UC-NRLF
i
CONCRETE ROADS
CONCRETE ROADS * 0
and Their Construction
BEING A DESCRIPTION OF THE CONCRETE ROADS IN THE UNITED KINGDOM, TOGETHER WITH A SUMMARY OF THE EXPERIENCE IN THIS FORM OF CONSTRUCTION GAINED IN AUSTRALIA, CANADA, NEW ZEALAND AND THE UNITED STATES OF AMERICA
'CONCRETE SERIES
PUBLISHED BY
CONCRETE PUBLICATIONS LIMITED
4, CATHERINE STREET, ALDWYCH, LONDON, W.C.2
Price Eight Shillings nett
FOREWORD
ONE of the most pressing problems of the time in connection with public works is that presented by the necessity for improved roads to meet the demands of modern traffic conditions, which have resulted from the enormous development of motor transport during recent years.
The adoption of concrete is a serious attempt to grapple with this problem, which really resolves itself into a search for the ideal road, and so many of our thoroughfares and highways are insistently calling for speedy reconstruction that the present would seem to be an opportune time for approaching the question dispassionately and without prejudice, examining it in the light of recent experience and determining whether the time has not arrived for giving the concrete road a fair trial in this country. True, our acquaintance with modern traffic conditions has been brief, but, brief as it may be, it is sufficient to form a clear indication of our future needs and to serve as a guide for future methods.
Frequent reference has been made in the public Press to the head- way made by concrete roads in America, where, owing to the wide adoption of motor transport, the road question has assumed serious proportions for years past. Thousands of miles of concrete road are in use there, and something like 75,000,000 sq. yds. are in con- templation during the present year. It cannot be supposed that a nation so keen at weighing up the possibilities of a business propo- sition would, after fourteen years' experience, continue to lay these roads on such an extensive scale were they not entirely satisfied as to their efficiency and economy. As might have been expected, there were partial failures, particularly in America, in the early days, but only in this way is progress attained — and the progress has, indeed, been great, both in the United States and in the United Kingdom — and even to-day, greatly as methods have improved, no sane person would venture to say that concrete road practice has reached finality.
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viii FOREWORD
The experimental stage is, however, long since past ; we have the advantage of American experience as well as our own to serve as a guide for future practice, and, claiming as we do that the con- crete road approaches more nearly to the ideal than any other, we maintain that, as Mr. H. Percy Boulnois, M.Inst.C.E., said in his report to the Roads Improvement Association, it should "be included in the practice of road building, and should be given a better chance in the future, than it has received in the past, to prove or disprove its merits." Should this opportunity not be given, progress here must inevitably be slow. But we believe it will be acknowledged that the records we present of roads laid in the United Kingdom are suffi- cient to show that this form of construction is quite sound, and that from the point of view of efficiency the concrete road is entirely justified ; while comparative figures have clearly proved that its initial cost is little in excess of, and its ultimate cost is appreciably lower than, that of any other type of road.
In the following pages particulars are given, as far as it has been possible to obtain them, of the various concrete roads that have been laid in this country up to the time of going to press, and the methods adopted in their construction. Every effort has been made to pre- sent a complete survey of the work done, and to this is added the latest information obtained from the officials concerned with regard to the condition of each road. It will be seen that these communications are all strongly in favour of the concrete road, and there is thus established a valuable summary of evidence from those best able to form an opinion from the point of view of the road authorities. A chapter has been devoted to roads in other countries, for the account in which of the concrete roads in America we are indebted to the courtesy of Mr. Thomas J. Harris.
For the chapter on mechanical devices as applied to concrete roadmaking we have had the advantage of the services of Dr. A. B. Searle, and our thanks are due to the various engineers and surveyors mentioned who have willingly supplied us with information.
December, 1920. THE EDITOR.
CONTENTS
PAGE
CHAPTER I CONCRETE ROADS IN THE UNITED KINGDOM
METROPOLITAN ROADS — Southwark — Deptford.
CHAPTER II
CONCRETE ROADS IN THE UNITED KINGDOM (continued) . 10 PROVINCIAL ROADS — Berkshire — Cheshire — Cornwall — Devonshire — Essex — Hampshire — Kent — Monmouth- shire— Northumberland — Somerset — Scotland — Ireland.
CHAPTER II [
CONCRETE ROADS IN INDUSTRIAL WORKS AND MILITARY CAMPS . . . . .... 69
Port of London Authority — J. Baker, Sons and Perkins, Willesden Junction — Empire Paper Mills, Greenhithe, Kent — Factory at Southampton — Portsea Island Gas- works, Portsmouth — Swindon, Great Western Railway — Purfleet, Messrs. Jurgens, Ltd. — Belfast, Messrs. Harland & Wolff— Hamilton Road, Belfast Harbour Co mmissioners — London, Brighton & South Coast Rail- way (Goods Yard) — Chisledon — Loch Boon — Cardiff, Messrs. Lewis & Tylor, Ltd. — Tredegar, Powell Duffryn Steam Coal Co., Ltd.
DC
x CONTENTS
PAGE
CHAPTER IV
CONCRETE ROADS IN OTHER COUNTRIES .... 99 New Zealand — Australia — Canada.
CHAPTER V
THE GROWTH OF CONCRETE ROADS IN THE UNITED STATES. 115 American Roads and their Development up to 1920.
CHAPTER VI
MECHANICAL DEVICES FOR MAKING CONCRETE ROADS. . 124 Appliances used for Preparing the Road-Bed — Preparing the Concrete — Laying the Concrete — Tamping and Fin- ishing the Concrete.
CHAPTER VII CONCRETE KERBING ... . . . -. . 168
CHAPTER VIII
SUGGESTIONS FOR THE PREPARATION OF SPECIFICATIONS FOR CONCRETE ROADS . . . . . . . * 177
CHAPTER IX
THE USE OF CONCRETE FOR ROAD ACCESSORIES . . 185
INDEX . . ..... . 195
LIST OF ILLUSTRATIONS
PAGE
ABERGAVENNY AND BRECON MAIN ROAD . . . , 54 ADAMS "LEANING WHEEL" GRADER . , , . 136
ANDREWS ROAD, GEORGIA . . . . • .120
BACKFILLER (GASTON) . , . . . . . .136
BARBER-GREENE LOADER ....... 149
BAXTER'S BALLAST- WASHING AND GRADING MACHINE . . 145 BRECON-ABERGAVENNY ROAD . . . . . .<• . 54
BRIDGE STREET, TAUNTON .. . , . . . 58
BROCKHAM STREET, SOUTHWARK ...... . 3
CANMORE STREET, DUNFERMLINE . . . .. 61, 63
CHISLEDON CAMP . . . . . .* . 91
CHTJRCHLAND ROAD, VIRGINIA . . . • >.' • .120 COAST ROUTE, SAN FRANCISCO TO Los ANGELES . .123 CONCENTRIC CYLINDER SCREEN . . . *. . .139 CONCRETE KERB LAID IN 1881 IN BRIGHTON . * . 171 CONCRETE KERB, PITCHER AND CEMENT PAVING LAID IN
BRIGHTON, 1878 . . . , -. *. . 171
CONSTABLE WAGON . . . . . . . 152
CRANE AND GRAB ........ 130
CROSS SECTION OF PART OF CONCRETE ROAD, SHOWING SUGGESTED SECTION OF OUTSIDE EDGE WHERE NOT SUPPORTED BY KERB ING . . . . . .183
CULVERT . .. . . . . . . 187
"DEVIL" DISINTEGRATOR . . . * . . 142
DOCK ROAD, SOUTHAMPTON ... . . .42
DOCK ROAD, TILBURY 35, 37, 40
DRAG-LINE EXCAVATORS 133
EPPING NEW ROAD, BUCKHURST HILL .... 33
ERIE SHOVEL 127
ERIE SHOVEL WITH GRAB 130
FOREGATE STREET, CHESTER 20
GLENGORMLY, BELFAST, CONCRETE ROAD AT . .66
GRAVESEND, ROAD NEAR 45, 48
xi
xii LIST OF ILLUSTRATIONS
PAGE
HALL'S DISINTEGRATOR . . ; . . . . 142
HAMILTON ROAD, BELFAST ...... 94
HEPBURN CONVEYOR . . . . . . .136
JUBILEE WAGONS . . . . . . 133
KERB AND CHANNEL IN THE BOROUGH OF AYLESBURY . .169
LADDER EXCAVATOR . 133
LAMP POST . .... . . . . 190
LOCH DOON CAMP . . 87
LONDON-DOVER ROAD, GRAVESEND .... 45, 48
LONGHOUGHTON ROAD, NORTHUMBERLAND . . .56
LOWER BRISTOL ROAD, BATH . . . . . . 58
LUTE TO PLACE CONCRETE, USE OF . . ' . . .161
MANHOLE . - . . . . . . . . 187
MARINE DRIVE, EXMOUTH . . . . . 26, 27
METHOD OF CONSTRUCTING SUBMERGED CONCRETE KERB IN
SURREY 174, 175
MILWAUKEE PAVER . . . . . . . . 164
MORRISON ROAD, COLORADO . : ' . . . . .117
MOULD FOR KERBS AT BRIGHTON . . .• ; . 173
MOUNTNESSING ROAD . . . . . . 31, 32
NEW KING STREET, DEPTFORD . . . . ... 7, 8
NEWPORT-CARDIFF ROAD . . . . . . .52
NEW SOUTH HEAD, WOOLLAHRA ROAD, SYDNEY . . . 103
NORTHBROOK STREET, NEWBURY . . . . 11, 13, 14
PADSTOW STATION . . . . . . . .23
PAVEMENT GUTTER IN THE BOROUGH OF AYLESBURY . .169
PIPES 190
PIPE -LINE EXCAVATOR . . . . . . .130
PORT OF LONDON AUTHORITY: ROAD IN COURSE OF CON- STRUCTION AND FINISHED ROAD . . . . . 71
PRIESTMAN GRAB . . 127
PYRAMIDAL INTERLOCKED REINFORCEMENT FOR ROADS, RAFTS, FLOORS, ETC., AS USED FOR THE PORT OF LONDON AUTHORITY ........ 70
RANSOME ELEVATOR . . . . . . .152
RANSOME HAND -MIXER 152
RANSOME MIXER ........ 158
RANSOME SELF-CONTAINED MIXER . . . . .155
REX MIXER ......... 158
REX PAVER . . . . . . . . .160
ROAD-LAYING MACHINE USED BY THE PORT OF LONDON
AUTHORITY .... 166
LIST OF ILLUSTRATIONS xiii
PAGE
ROBERTS LANE, CHESTER ... .16
RUSTON AND HORNSBY EXCAVATOR . . . . .127
ST. KILDA ROAD, MELBOURNE 103, 106
SALT LAKE CITY, CONCRETE ROAD NEAR . . . .117
SELF-PROPELLING TEMPLATE AND TAMPER . .165
SIDMOUTH ROADWAY AND FOOTWAY ..... 27
SMITH HAND-MIXER . . . . . . .155
SPECIAL ROAD FORMS . . . . . . .161
STATION NAME PLATE . . . . . . .190
STEEDMAN STREET, SOUTHWARK ..... 3
TELEGRAPH POLE . . . . . . . .190
TEMPLATE 183
TORONTO -HAMILTON HIGHWAY ..... 109, 113 TOTNES-PAIGNTON ROAD .... Frontispiece and 30
TREE GUARD 187
TRENCH TAMPER . 139
VICTORIA MIXER . . . . . . . .158
VICTORIA MIXER WITH BUCKET DISTRIBUTOR . . .160
WHITEFRIARS, CHESTER . . . . . . .18
WINGET CHAIN SPADES . . . . . . .158
WINGET CRUSHER . . . . . . . . 139
WINGET MIXER 158
WINGET SELF-CONTAINED WAGON LOADER . . .149
WORKS ROADS : —
BELFAST : HAMILTON ROAD ..... 94
BELFAST : HARLAND & WOLFF'S SHIPYARDS . .94
CARDIFF: LEWIS & TYLOR 98
EAST CROYDON : LONDON BRIGHTON AND SOUTH COAST RAILWAY GOODS YARD ...... 90
GREENHITHE : EMPIRE PAPER MILLS . . . .79
PORTSMOUTH : PORTSEA ISLAND GAS WORKS . 82, 83, 85
PURFLEET : JURGENS, LTD. ... 75, 95
SOUTHAMPTON : FACTORY ROAD ..... 79 S WIND ON : GREAT WESTERN RAILWAY . . .91
TREDEGAR: POWELL DUFFRYN STEAM COAL Co., LTD. . 98 WILLESDEN JUNCTION : JOSEPH BAKER, SONS AND
PERKINS 74
CHAPTER I
CONCRETE ROADS IN THE UNITED KINGDOM
A. METROPOLITAN ROADS
Southwark
Mr. Arthur Harrison, M.Inst.C.E., the Borough Engineer of South- wark, has long been convinced of the value ot the concrete road, and under his recommendation a stretch of concrete roadway was laid as an experiment in Penton Place in August and September, 1918. The success of this having been assured, the Southwark Borough Council laid down a programme for nine concrete roads, all of which have now been constructed, and so satisfactory have they proved that a more extensive scheme still has been decided upon, to include a total of twenty- five roads and streets by the end of 1920. At the time of going to press twenty-one of these have been completed.
Penton Place. Half of this roadway was laid in concrete as an experiment in August and September, 1918, and the remainder in 1919, being opened to traffic on December 19. Its length is 370 yds., and the area 2,680 super, yds. The traffic is described as being part heavy and part medium.
Amelia Street. Length — 320 yds. ; area — 1,940 super, yds. ; opened to traffic — July 14, 1919; nature of traffic — part heavy, part medium.
Steedman Street. Length — 193 yds. ; area — 1,630 super, yds. ; opened to traffic — August 16, 1919 ; nature of traffic — heavy coal traffic in winter.
Warner Street. Length — 220 yds. ; area — 2,459 super, yds. ; opened to traffic — October 1, 1919 ; nature of traffic — heavy.
Standard Street. Length — 186yds. ; area — 1,141 super, yds. ; opened to traffic — October 21, 1919; nature of traffic — part heavy, part medium.
1 B
: 2-": ;•• :.: ••:..: /;. .CONCRETE ROADS
Brockham Street. Length — 85 yds. ; area — 710 super, yds. ; opened
to traffic — November 6, 1919 ; nature of traffic — light. Content Street. Length — 93 yds. ; area — 538 super, yds. ; opened
to traffic — January 10, 1920 ; nature of traffic — light. Wadding Street. Length — 163 yds. ; area — 1,013 super, yds. ;
opened to traffic — January 10, 1920 ; nature of traffic — -medium. Queen's Row. Length — 182 yds. ; area — 1,440 super, yds. ; opened
to traffic— February 12, 1920 ; nature of traffic— light. Westmoreland Road. Length — 217 yds. ; area — 1,920 super, yds. ;
opened to traffic — March 26, 1920; nature of traffic — medium. Trafalgar Street. Length — 340 yds. ; area — 3,000 super, yds. ;
opened to traffic — April 3, 1920 ; nature of traffic — medium. Thurlow Street. Length — 533yds. ; area — 3,700 super, yds. ; opened
to traffic — June 3, 1920 ; nature of traffic — medium. South Street. Length — 177 yds. ; area — 1,479 super, yds. ; opened
to traffic — June 26, 1920 ; nature of traffic — medium. Wooler Street. Length — 80 yds. ; area — 573 super, yds. ; opened to
traffic — July 10, 1920 ; nature of traffic — light. Avenue Road. Length — 80 yds. ; area — 614 super, yds. ; opened to
traffic — July 24, 1920 ; nature of traffic — fairly heavy. Heiron Street. Length — 217 yds. ; area— 1,637 super, yds. ; opened
to traffic — August 7, 1920 ; nature of traffic — medium. Deverill Street. Length — 275 yds. ; area — 1,890 super, yds. ; opened
to traffic — November, 1920 ; nature of traffic — medium. Lawson Street. Length — 35 yds. ; area — 280 super, yds. ; opened to
traffic — November, 1920 ; nature of traffic — medium. Lorimore Street. Length — 350 yd?. ; area — 3,010 super, yds. ; opened
to traffic — November, 1920 ; nature of traffic — medium. Ralph Street. Length — 112 yds. ; area — 733 super, yds. ; opened to
traffic — November, 1920 ; nature of traffic — medium. Theobald Street. Length — 200 yds. ; area — 1,206 super, yds. ; opened
to traffic — November, 1920 ; nature of traffic — medium.
The other roads to be laid in this borough by the end of 1920
are Alsace Street, Alvey Street, Hill Street, and Mina Road,
and 5,000 additional yards are to be laid in Westmoreland Road. The general method adopted is the same for all, although Mr.
Harrison states that each street laid taught them something new,
and that, therefore, the whole scheme so far has been one of
continual progress, each road being an improvement in various
small details upon the one previously laid.
Construction. — The original roadway was of granite macadam,
FIG. 1.— Concrete road in Brockham Street, Southwark. The end of a day's work. Note the planks by means of which the vertical edge is formed.
\
FIG. 2.— Concrete road in Steedman Street, Southwark. This thorough- fare has been open to traffic since August, 1919. Although the photograph was taken soon after a heavy shower of rain, it will be noticed that, with the exception of a few damp patches, the road is already dry,
3
IN THE UNITED KINGDOM— METROPOLITAN 5
and this was excavated to a depth of 9 in.. The foundation, which was found to be fairly solid, received no special prepara- tion, and after being rolled was ready to receive the concrete.
The two -course method was adopted, the lower being 4 in. thick and the wearing coat 2 in., the latter being laid before the former had set, so that the whole might form one monolithic structure. The concrete for the lower consisted of a 6 : 1 mixture, and the material from the old macadam road was used as the aggre- gate. The upper course was composed of a 3 : 1 mixture, the aggregate in this case also being the material from the original road, crushed, washed and graded from £ in. down.
By the use of the material from the old roadway a very consider- able economy is effected by the elimination of costs for the purchase and transport of new aggregate.
With a view to further economy, the Council, in 1919, purchased a washing and grading machine which has already more than paid for itself. (See Chapter VI.)
The reinforcement was placed 2 in. from the bottom, i.e., in the middle of the bottom course. It consists of f in. rods simply interlaced, like bedstead laths, and wired at the ends, succes- sive lengths being joined to each other by being hooked together.
The method of laying alternate sections was not adopted, but each day's work was finished off by a clear vertical edge as shown in Fig. 1, against which the next day's work was butted without the intervention of a joint filler of any description. The reinforcement does not extend over these joints, so that each section consists of a slab of reinforced concrete in itself.
The contour was formed by the use of pins, which were removed as the work proceeded.
For finishing the surface, a special tool has been devised, which consists of a metal plate 15 in. square, to which is attached a handle fixed obliquely so that the tool can be operated from the side of the road. The surface was rubbed over with this tool, and parts of the road which were found to be too smooth were roughened with a bass broom.
The joints were tarred first, and after an interval of some weeks the whole road was coated with tar and sand. This gives a sur- face which is not too smooth and which affords a good grip for horses and wheels.
The traffic was kept off the road for about three weeks.
The roads in question are of varying character. Whilst not
6 CONCRETE ROADS
themselves main roads, several of them link up one main road with another, and all, therefore, carry a fair traffic, which on some of them may be described as heavy.
The average cost of the roads so far laid in concrete is 12 s. Qd, per super, yard, which, having regard to the low maintenance cost, compares very favourably with macadam, the maintenance cost of which is very high in Southwark. The Borough Engineer is of the opinion that macadam is quite unsuitable for town roads and streets, and has the utmost confidence in concrete, which he believes will in all cases ultimately be cheaper than any other form of road construction.
It is noteworthy that the majority of the men employed for this work were recently demobilized men who had never previously done any work of this kind and were trained by the Engineer's staff.
Fig. 2 shows one of the roads open to traffic.
Latest Report. — In November, 1920, Mr. Harrison stated that in two streets weaknesses appeared, but only over very limited areas, and there was nothing which could be termed a failure. The principal weakness was in Warner Street. This is thought to have been due to want of care in curing. In Steedman Street one weak place developed, the cause of which was believed to be want of consolidation along the " joints " at the beginning of the day's work.
All the other streets opened to traffic on the date named were in excellent condition.
Deptford
New King Street. — This road was laid under the supervision of the late Borough Surveyor, Mr. F. Wilkinson, A.M. I.C.E., and certain features render the construction unique.
The length of the street is about 350 yds., and the average width 16 ft. The traffic passing through this thoroughfare, though it is not a main road, is said to be amongst the heaviest in London, since the street leads to the entrance of the Supply Reserve Department, and owing to the narrowness of the road, which does not admit of any spreading out of the traffic, the whole weight and impact is concentrated within narrow limits. This constitutes a very severe test.
The two special features of this road are : — 1. Double reinforcement, one layer being placed near the top, and the other near the bottom.
IN THE UNITED KINGDOM— METROPOLITAN 7
2. The dipping down of both concrete and the lower reinforce- ment under the kerb and up on the inside as shown in Fig. 3 ; the kerbs are of granite.
The lower reinforcement takes the stresses due to the weight of the traffic in the usual way ; the object of the upper reinforce- ment is to take the stresses due to the horizontal motion of the traffic, the theory being that there is a tendency for the particles of concrete in front of a moving wheel to be pushed forward, with a reverse tendency in the case of the particles behind the wheel. Between those two a tensional stress is set up, and it is to take this stress, and so prevent cracks, that the upper reinforcement is intended. It is also considered that the double reinforcement
METROPOLITAN BOROUGH OF DEPTFORD
Concrete Road
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Depth of Concrete 9*
FIG. 3. — Transverse section of the concrete road laid in New King Street, Deptford, showing the kerbs embedded in concrete.
renders expansion joints unnecessary ; these were, therefore, not provided.
Construction. — No special foundation was prepared, as the sub- grade of the original road was found to be sufficiently firm for the purpose.
The road was constructed in two courses, a lower, 6£in., and an upper, 2£ in. On account of the upper reinforcement it was not possible to lay the surface coat before the concrete of the lower had set ; the former was, therefore, laid 24 hours after the latter, this being the earliest time at which the men could get on to the concrete to place the second or upper reinforcement in position.
CONCRETE ROADS
The lower reinforcement was first placed in position 2 in. from the bottom. To keep it in place the mesh was stretched over a 2 -in. plank, and was supported elsewhere by portions of concrete passed through a mesh. The wet mixture was then deposited to a depth of 6J in. and left until next day. After an interval of 24 hours the top reinforcement was placed and supported in position £ in. above the surface of the lower concrete, and the wearing coat put in to a depth of 2£ in. — J in. below thereinforce-
FIG. 4. — Concrete road under construction in New King Street, Deptford. The reinforcement for the lower course, stretched over a 2 inch plank to keep it in position, is seen in the foreground.
ment and 2 in. above it. Thus the depth of the concrete for the whole was 9 in.
The surface was finished with a wooden float.
The amount of camber was 1 in 48, to obtain which a screed was used. This, which was very shallow, remained in position until the concrete had set. It was then removed, the trench extended down to the first reinforcement and filled with the same mixture as the wearing coat.
Unwashed Thames ballast graded up to 1 in. was used for the lower course in the proportion of 6:1, and Mount Sorrel chip- pings and sand 3 : 1 for the wearing coat ; the former passing a f in. sieve. Fig. 4 shows this road in course of construction.
IN THE UNITED KINGDOM— METROPOLITAN £
It was not proposed to surface the road with tar, but to test' it, at any rate for some months, as an unsurfaced concrete road. An experiment was, however, being made in material in the fol- lowing way with a view to ascertaining which treatment produced the best results in point of wearing quality.
The length of the road was, for this experiment, divided into four sections, in each of which a different treatment has been adopted for the wearing coat, thus : — •
Section 1. Wearing coat plain 3 : 1 concrete.
Section 2. Same as section 1, but sprinkled with powdered carborundum.
Section 3. Plain 3 : 1 concrete with a different brand of cement.
Section 4. Same as No. 3, but sprinkled with carborundum.
The carborundum was laid to prevent horses from slipping. It was, of course, applied while the concrete was wet, and was not tamped, but allowed to sink in by its own weight.
After the concrete had set sufficiently hard the surface was covered with damp sand to a depth of 2 in. or 3 in., and the traffic was kept off the road for a month.
The cost of this road was 17s. per super, yard, but now that the men have experience in this form of work it is expected that the next concrete road will be laid at a cost of from 105. to 125. per yard.
The road has been open to traffic for eighteen months, and w'th the exception of two or three small surface cracks and a pot-hole at one of the joints, the road is in a good condition.
In a report, dated July, 28, 1920, the Borough Surveyor states that this road was tar-sprayed for the first time on May 10, 1920. "It was treated with a very thin coat of tar and covered with fine sand. The present condition is good."
Latest Report. — The Borough Surveyor, Mr. H. Morley Lawson, in his report in November, 1920, on the present condition of the road. . attributes the pot-hole, mentioned above, to careless floating after the surface screed was removed ; this conclusion was arrived at from the fact that all the other joints are perfect and show little deterioration. The cost of repairing this pot-hole will be small.
As before stated, the road takes all the heavy traffic going to and from the Supply Reserve Depot, which is ever increasing, and on account of the narrow width of the road the test to which it will be submitted is severe.
CHAPTER II
CONCRETE ROADS IN THE UNITED KINGDOM
B. PROVINCIAL ROADS
Berkshire
Northbrook Street, Newbury. — Northbrook Street is the main business street of Newbury, and, being part of the main road between the Midlands and Southampton, bears a fairly heavy traffic of a general character.
This road, which was laid in the spring of 1920, is 440 yds. long, and the width of the roadway, from kerb to kerb, is 45 ft. ; this enabled the reconstruction to be carried out in half widths without undue inconvenience.
Construction. — The particulars of construction are as follows : —
Foundation. — The foundation is that of the original macadam road, and is fairly well consolidated.
Course. — For the concrete road itself the one -course method was adopted, and the thickness of the slab is 8 in.
Aggregate and Proportions. — The materials were mixed by hand in the following way : A measuring box of one-third cu. yd. capacity was employed, and this was filled,
Once with 2 -in. Glee Hill granite,
Once with 1-in. to £-in. Clee Hill granite, and
Once with sharp sand and flint grit.
This gives 27 cu. ft. of aggregate, to which was added 6 cu. ft. of Portland cement, resulting in a 4£ to 1 mixture.
Reinforcement. — The subsoil here is peat, and it was solely with a view to counteracting its effect upon the road surface that reinforcement was employed. For a like reason the concrete was treated as a slab, and the reinforcement placed 2J in. from the under side.
10
IN THE UNITED KINGDOM— PROVINCIAL 11
FIG. 5. — The concrete road in Northbrook Street, Newbury, before being opened to traffic.
FIG. 6. — The concrete road in Northbrook Street, Newbury, after being opened to traffic.
IN THE UNITED KINGDOM— PROVINCIAL 13
Joints. — There are no transverse joints, the end of each section being finished with a vertical face, and the concrete of the next section butted up against it.
At the sides the construction presents a feature which appears to be a novelty. Between the longitudinal edge of the road slab which runs underneath the kerb (to which reference will be made later) and the outer edge of the footpath foundation a space of 2 in. was left. This formed a groove or trench 2 in. wide and 8 in. deep, running under the kerb the whole length of the roadway on each side, so that should there be any lateral expansion in the concrete a 2 -in. space is provided in which such movement can take place. This is seen in the section, Fig. 7.
FIG. 7. — Transverse section of the concrete road in Northbrook Street, Newbury. On the right is a double kerb, necessitated by the higher level of that side of the street.
Finish. — The surface was not floated, but tamped with a cam- bered iron-shod screed, 2 in. by 9 in. The surface obtained is very fine from the point of view of " grip " for horses and motor- vehicles.
Surfacing. — Traffic was kept off each portion for one month, and the road was tarred and gritted the day before being opened to the public.
Camber. — A fall of 1 in 50 is allowed from centre to side, and the flatness of the finished concrete portion, with its consequent freedom from skidding, is very striking when compared with the camber of the original road.
Footpaths. — The footways practically throughout the town are of concrete, laid in situ in slabs 6 ft. wide with £-in. joints formed with wooden strips, which are left in place. Those in the main street have been down for 23 years and are in remarkably good condition. In some cases the aggregate was composed of gravel and in others of granite chips.
14
CONCRETE ROADS
Kerbs. — In Northbrook Street the kerbs (of concrete) were laid in situ with £-in. joints, as in the case of the footways them- selves.
A-? the original footpaths were being retained, an outer form only was required for the kerb. This was placed in position on the road slab and about four or five inches from the edge, so that the outer portion of the kerb rests upon -the roadway itself.
Before placing the concrete for the kerb, a strip of tarred paper was laid in the bottom of the trench formed by the edge of the pavement and the outer form. This strip, which may be seen
FIG. 8.— Concrete road in Northbrook Street, Newbury, The kerb is here seen under construction. In the foreground the strip of tarred paper will be observed lying in the bottom of the trench. The form is kept in position by spacers on the inside and blocks of stone on the outside.
in Fig. 8, covered over the 2-in. space which has been mentioned above and which acts as a longitudinal joint to the roadway. The concrete was then placed in position up to the level of the footpath, and finished off with a steel trowel. The appearance of the finished kerb is very neat.
Cost. — The total cost cannot, at the time of going to press, be given exactly, but is expected to work out at approximately £1 2s. Qd. per super, yard. As prices rule to-day this is not high, and in the present instance is regarded as eminently satisfactory.
16: : PI
1 CONCRETE ROADS
FIG. 9. — Showing metal reinforcement and the placing of the surface concrete, Roberts Lane, Chester.
. 10. — View of completed road, Roberts Lane, Chester.
IN THE UNITED KINGDOM— PROVINCIAL 17
Northbrook Street has always been a bad roadway, and for 20 years prior to the war had cost £300 per annum in maintenance. To-day, if retained as a macadam road, it would cost something like £500 per annum.
The concreting of this road will cost somewhere about £5,000, and as the interest on this at, say, 6 per cent., will amount to £300 only, it will be seen at once that the contention of Mr. S. J. Lee Vincent, A.M.I.C.E., the Borough Surveyor, that the laying of a new concrete road is a sound commercial pro- position, is borne out by actual figures.
It is anticipated that, when the present road has had time to prove itself, other concrete roads will be laid in the borough.
Latest Report. — In December, 1920, the Borough Surveyor stated that, in order to give a real concrete road a thorough test, all top dressing was omitted with the exception of a thin coat of refined tar and granite chippings. After seven months of heavy traffic, the surface is in a thoroughly satisfactory condition.
Cheshire
Roberts Lane, Saltney, Chester. — One of the first reinforced concrete roads to be constructed in this country was Roberts Lane, Saltney, in the environs of Chester, laid in 1912, under the personal super- vision of Mr. Matthews Jones, late City Surveyor. Briefly de- scribed, this road, which is 950 ft. long and 20 ft. broad, was excavated to a depth of 8 to 10 in. On top of the clay subsoil 2 in. of cinders were placed to bind it, and on this 2£ to 3£ in. of concrete. Across the road the reinforcement was then laid. Covering this was concrete to a depth of 3£ to 4| in. The concrete was made of five parts broken granite f in. to £ in. and sharp sand mixed to one of cement. The road was closed for about three weeks, and for part of the time was kept well watered. After being opened for traffic, the road remained for nearly a year without any- thing being done to it, when it was tar-sprayed and sprinkled with granite chippings, at a cost of \\d. per yard. This treatment is car- ried out once a year, so the cost of maintenance is a very light one. The traffic on this road in 1913 was computed to be about 60 tons per day — not heavy — but undoubtedly this has increased, and will still further do so as the property in and around this district is developed. The original cost, including the excavation, was 3s. lOd. per yard, and the cost of maintaining the surface has already been mentioned,
18 CONCRETE ROADS
Latest Report. — When this road was inspected in the May of 1914, the surface was in perfect condition. In the spring of 1915 the tar-spraying, etc., was done, and when seen again in August, 1919, the surface was still in complete order, and there was not the slightest sign of the dressing lifting in any way. On this point it is well worth remembering that when the tar spraying and chippings were first put down, the concrete was thoroughly dry and hard.
FIG. 1 1 .—View of completed road, Whitef riars, Chester.
Whitefriars, Chester. — This road, which is 510 feet long and 15 feet wide, was laid in August, 1914. It was originally a road made with wooden blocks resting on a concrete foundation. The foundation, having been broken up at different times for various repairs, was not in good condition. Two inches of concrete were put in, after which the metal reinforcement was placed across the road, and upon the reinforcement a further 4 in. of concrete was laid. This was a 6 to 1 mixture composed of four parts Welsh granite, graded from \ to 1 in., two parts fine sharp sand and one part cement. On completion the road was closed for three weeks, kept well watered, and then opened to traffic. Somewhat later it was tar-sprayed and granite chippings were put on. The cost of this road, including excavation, was 6s. 3d. per yard super.
Latest Report. — Speaking at the Roads and Transport Congress, held in London at the end of 1919, Mr. Matthews Jones, the City Surveyor, stated that his Highways Committee had been so satisfied with the results obtained that permission had been given
20
CONCRETE ROADS
FIG. 12. — Road in course of construction, Foregate Street, Chester.
FIG. 13. — A portion of completed road, Foregate Street, Chester.
IN THE UNITED KINGDOM— PROVINCIAL 21
to lay a further reinforced concrete road right through the main thoroughfare of the City of Chester, namely, Foregate Street and Eastgate Street. .
Foregate Street and Eastgate Street, Chester.— This street takes all the through traffic from Manchester, Warrington and Liverpool to North Wales, and, speaking roughly, there is not less than 1,500 tons of traffic passing over the roadway each day. Along the centre of these streets is a double line of tramway track which was concreted in at the same time. So far, only a portion of the road has been completed and opened to traffic, but up to now the results have been all that were anticipated. Very careful observations are being made, and in the event of any defect developing it will be possible, from the statistics obtained, to find the cause and so remedy it in the future. The sanction of the Local Government Board was received to do this work, and the Road Board have shown their interest in the experiment by granting the full estimated amount for carrying it out, viz., £5,000. The reconstruction of this road was estimated for early in 1919, at a cost of lls. 3d. per super, yard, but up to now the cost has been 12s. Qd per super, yard ; this is owing to the increase in the cost of materials and of labour.
If this scheme proves a success, application will be made for permission to deal with eight miles of roads' in Chester in a similar manner. Mr. Matthews Jones stated in his paper that if the eight miles of roads are reconstructed with reinforced concrete, the estimated cost will be 13s. per super, yard, making a total of £82,368. If the work were done with granite sett paving on concrete foundation he could not, in Chester, estimate a lower cost than 25s. per super, yard, or a total of £158,400 ; or, again , if it were done with tar-macadam, including a foundation, 17s. per super, yard, or a total cost of £107,712.
The method adopted for laying this main street was as follows : The concrete was mixed in the proportion of 5 to 1. The granite used was of the following sizes : 1£ in., 1 in., f in., and \ in. These were mixed in equal proportions. The concrete consisted of 3£ of granite, \\ of clean sharp sand, to 1 of cement. When the concrete surface had been completed— that is, after it had been trammelled to the contour and allowed to set — the surface was tar-sprayed and covered with i-in. granite chippings.
Our two illustrations, Figs. 12 and 13, show the road in course of construction, and a portion of same after completion,
22 CONCRETE ROADS
Cornwall
PadstOW Station. — This road is on the Fish Quay at Padstow, on the London and South-Western Railway, and was laid towards the end of 1914. Its length is 107 ft. and width 20 ft.
Since it was thrown open it has so well stood the test of prac- tical use that there is no sign of wear. In the formation of this road there was first laid 2 in. of cinders, on this 3 in. of con- crete, consisting of five parts of broken granite f in. and small and sharp sand mixed, to one of cement. Across the roadway on the top of the concrete reinforcement was placed. Covering this was concrete of the same character as previously described to a depth of 3 in., the surface being roughly smoothed over. For three weeks the road was closed to traffic, and for the first nine days the concrete was kept well watered.
The illustrations, Figs. 14 and 15, show the road in course of construction and when finished.
Latest Report, November, 1920. — Mr. A. W. Szlumper, Chief Engineer of theL. &S.-W. Railway, states that the present condi- tion of the roadway is very good, and the cost of maintenance since the road was opened has been nil.
Devonshire
The Marine Drive, Exmouth, is one mile in length and has a total width of 65 ft., viz., carriage way 39 ft. 6 in., footpaths 5 ft. 6 in. and 20 ft. wide respectively.
The carriage-way is concrete 5 in. thick on a sand underbed between concrete kerbs. Felt expansion joints were placed every 24 ft.
The reinforcement is placed 2 in. from the surface.
The concrete was composed of six parts of beach gravel, fine and coarse proportionately, to one part Portland cement.
A trial portion was laid in May, 1915, and after six weeks was tar-sprayed one coat. Traffic was put on three weeks later and restricted to a width of 8 ft. of the carriage way in order seriously to test the concrete. Considerably more than 1 ,000 tons passed over this narrow portion between May and November, and there was not the slightest sign of wear.
IN THE UNITED KINGDOM—
FIG. 14. — Padstow Station. Fish Quay road under construction.
FIG. 15. — View of finished road, Fish Quay, Padstow.
t .\CONCRETE ROADS
FIG. 16. — Marine Drive, Exmouth, showing the trial portion, with concrete kerbs made on the site.
J
I
FIG. 17. — Marine Drive, Exmouth, during construction.
IN THE UNITED KINGDOM-
-jr,"
FIG. 18. — View of finished road, Marine Drive, Exmouth.
Fia. 19. — A reinforced concrete roadway and footway at Sidmouth.
IN THE UNITED KINGDOM— PROVINCIAL 29
The remainder of this road was laid and completed in September, 1916.
The photograph, Fig. 16, shows the trial portion referred to, with concrete kerbs made on the spot.
Half a mile of this Marine Drive is an excellent example of the application of reinforced concrete to engineering ends — the piling of concrete reinforced with plain bars, the slope and parapet also of concrete reinforced with expanded metal and faced with limestone, and, as stated above, the roadway of reinforced concrete.
The engineer for the whole of the road construction and the half mile of reinforced concrete sea defence was Mr. Samuel Hutton, Engineer and Surveyor to the Exmouth Council.
Latest Report. — Mr. Hutton, reporting on the condition of this road in November, 1920, stated that its present condition was very good, and that the cost of maintenance during the whole period since the road was laid has been less than £5, except for tar- spraying, which averages Id. per super, yard per annum.
Although the question of expansion joints in concrete roads is debatable, after three and a quarter years' experience Mr. Hutton is not prepared to advise that they should be dispensed with, since in this particular case the road, which is nearly 40 ft. wide, has a southern aspect and is exposed fully to the sun's rays.
The area so far laid is about 20,000 super, yards, and an extension of another 6,000 yards in the immediate future is in contemplation.
This engineer finds that repairs can be done quite easily, and is of the opinion that concrete roads will be more economical than other types.
Totnes — Paignton. — An experimental section of reinforced concrete road was laid in December, 1919, on the main road between Totnes and Paignton.
The particular stretch was chosen owing to (1) its very damp nature ; (2) no proper foundation ; (3) narrowness ; (4) The fact of there being a convenient road where traffic could be diverted, thus permitting the section to be dealt with being closed. The road has a length of 100 yds., a width of only 16 ft., with the addition of a 3 ft. wide footpath, and was excavated to a depth of from 6 in. to 2 ft. in order to bring the bed to a gradient of 1 in 42-5.
Before concreting was started all drains were laid, these being placed under the footpath where possible.
30
CONCRETE ROADS
The aggregate used was composed of equal proportions of granite broken to sizes H in., 1 in., f in. and | in. free from dirt and dust ; the sand was washed River Dart sand. Cement was to the British Standard Specification.
Frequent tests for voids were made, as a result of which the proportion of material worked out at about 4| to 1. The mixture was turned three times dry and three times wet, care being taken that only sufficient water was added to bring the whole to a plastic consistency. The centre of the road for a width of 12 ft. was 6 in. in thickness, the remaining 2 ft. on each side being 10 ins. The reinforcement was placed 2| in. from the bed.
Very little ramming was done, the material bejng carefully deposited approximately to required levels and floated with a
FIG. 20. — Road between Totnes and Paignton.
long wooden template run on screeds of wood. No joints were provided for longitudinal expansion.
Over a week's frost was experienced whilst the work was in hand, which necessitated a stoppage, the section completed being covered with a layer of sand over which bags were placed. Care was taken to leave the edge of the work stepped, rough, and doubly reinforced/so as to form a good key when a recommence- ment was made. No injury was done by the frost, nor is the junction noticeable.
Five weeks after completion the surface was sprayed with refined tar and the road opened to traffic.
IN THE UNITED KINGDOM— PROVINCIAL 31
A regular motor-bus service, as well as heavy traction engine traffic, passes over the section daily.
Latest Report. — Mr. Andrew Warren, County Surveyor (Southern Division) writing in November, 1920, stated : "The road is as good to-day as when first reopened (January, 1920), and no com- plaints have been received of its being slippery. The noise when steel-tyred vehicles are running over the section is no greater than when macadam was employed."
Essex
Mountnessing. — This road, which was laid in 1915, is one of peculiar interest, inasmuch as the sides of it are composed of reinforced concrete, whilst the centre track, a little over 11 ft., is of water- bound macadam. Mountnessing is on the main road between London and Colchester. The length of the section under notice is about three-quarters of a mile, and the width 22 ft. 4 in. The subsoil in this locality is clay, but as in early days this road
FIG. 21. — Section : Road at Mountnessing, Essex.
from time to time had been dressed with gravel it was on the latter that the work of the new road was started. First of all the road was excavated to a depth of 7 in., except at the side, where the depth was 13 in. to provide for the kerb. A layer of 3 in. of ashes was placed on the loose gravel, then l£ in. of concrete, on which the metal reinforcement was laid, and on the top of this 3^ in. of concrete. On either side of the road is a concrete kerb rein- forced with one steel rod and sunk to a depth of 10 in. This stands 3 in. above the surface of the road, and is 5 in. wide. The kerbing was made and placed as the road progressed. The width of the reinforced concrete on either side of the macadam is 5 ft. 7 in., and supporting the macadam is a concrete abut- ment running down from the level of the road to a depth of 8 in.
As regards the water-bound macadam, which extended to a depth of 3 in., it is the old material scarified and a thickness of 2 in. of new macadam rolled into it and water-bound.
The whole of the concrete was made up of three parts of crushed ballast, graded so as not to exceed 1 in., one part of washed sand, and one part of cement,
32
CONCRETE ROADS
FIG. 22. — -Road under construction, Mountnessing, Essex.
It should be observed that the first intention was to use the reinforced concrete as a foundation for other material, but it was afterwards decided that the concrete should be employed for the whole thickness of this portion of the road, and this plan was carried out. Some time after laying, the surface was covered with a thin coating of tarred slag.
Fig. 21 is a diagram of the road, showing in a section from kerb to kerb the position of the concrete, reinforcement, macadam, etc.
This work was planned and arranged with the approval of the Road Board by Mr. Percy J. Sheldon, County Surveyor, and Mr. Alfred Lyddon, late Deputy County Surveyor, Essex.
Latest Report. — Mr. Sheldon, reporting upon the road in November, 1920, states that it is in very good condition, and the cost of maintenance has been practically nil. The road carries a very heavy traffic.
Epping New Road — Buckhurst Hill. — This road forms part of a great highway which runs from London, through Woodford, to Newmarket and Cambridge, and the portion which has been laid in concrete is the Epping New Road at Buckhurst Hill. It parries a weight of traffic of some 1,500 tons a day.
The stretch of concrete road originally designed was 500 yds.,
IN THE UNITED KINGDOM— PROVINCIAL
33
but owing to strikes and other labour difficulties, 235 yds. only have been possible up to the present.
The Epping New Road at this point is 27 ft. wide, and since it is a main road, the traffic could not be diverted ; one-half of the width of the road was constructed at a time, the other half remain- ing open for traffic.
Method. — The two course method was the one adopted at
FIG. 23. — The reinforced concrete road under construction at Buckhurst Hill.
Buckhurst Hill, the lower course being 5£ in. in thickness, with a wearing course of 2 in., making a total of 7£ in. At the channel on each side to the width of a foot from the kerb the depth of the concrete is 12 in.
The mixing was done by hand, and the upper course laid imme- diately after the lower, so that the whole forms one monolithic structure.
34 CONCRETE ROADS
For tho lower course local ballast was employed in the propor- tion of 6:1, and for the wearing course granite chippings and crushed granite graded from £ in. down, and mixed in the pro- portion of 3 : 1.
The original road was macadam, and since the foundation has proved to be thoroughly sound it received no special preparation other than shaping and hand ramming.
The road is reinforced 1£ in. from the bottom.
No transverse joints were provided, the material at the com- mencement of each day's work being butted against the vertical edge left at the end of the previous section. Next to the kerbs longitudinal joints filled with bituminous material have been provided.
For purposes of surface drainage the road is shaped to a camber of 1 in 50.
The surface was finished by being worked over writh a shaped board or straight-edge until the mortar had been brought to the top. When the concrete was thoroughly dry and hard it was tar-sprayed.
After the concreting was completed the road was kept sprinkled with water for several days ; the traffic was kept off for twenty- one days in the warmer weather, and twenty-eight days during the autumn weeks.
The surveyor for the county of Essex, Mr. Percy J. Sheldon, M.Inst.C.E., under whose supervision the work was carried out. reported as follows on the condition of the road.
Latest Report, November, 1920. — The cost of maintenance has been nil, and very heavy traffic conditions prevail. The road has been in use about five months.
Mr. Sheldon is convinced that there is no question as to the strength and durability of concrete for roads, and that their success and efficiency are only a question of workmanship.
It is interesting to note that all the bridges that are being re- newed in the area administered by the Essex County Council are being constructed in concrete, and there is every reason to anticipate an extensive development of concrete roads within the next few years.
Tilbury Dock Road. — The South Ward of Tilbury immediately adjoining the huge dock of the Port of London Authority lies well below the river level — the surface level being only four
IN THE UNITED KINGDOM— PROVINCIAL :}.">
Ordnance datum. The soil being alluvium for a depth of 40 ft. before the ballast is reached, considerable trouble was formerly encountered when erecting buildings or constructing roadways, because of the unequal settlement of foundations.
The success which attended the erection of some cottages by the use of reinforced concrete foundation. rafts caused the Council to look to a somewhat similar form of foundation for remedying the difficulties met within the heavily trafficked portions of their road system ; instructions were therefore given their engineer to prepare specifications for a trial length of concrete roadway with suitable reinforcement.
The experimental section was laid down on the main Dock Road during the months of September, October and November, and opened to traffic at Christmas, 1917. It is 130 ft. long, 27 ft. wide, and 7 in. thick.
<»**vryr
- -/?--»•
= SECTION-^
FIG. 24. — Reinforced concrete roadway, Tilbury.
The section is level longitudinally, with a cross-fall of 1 in 50.
It is on the main road leading from London to Tilbury Main Dock, where the Cunard, Atlantic Transport, Orient, Peninsular and other companies' large liners are berthed, and a summary of traffic statistics shows " heavy traffic," there being more than 250 vehicles daily in addition to tractors.
Before the new roadway was laid down, the road paving had consisted of water-bound macadam resting on about 1 ft. of hard core.
The eastern end of the roadway being the turning corner of ArrolTs Bridge leading to the Port Authority's property, the heavy lorries in turning caused deep ridges to keep appearing, and much nuisance from dust in dry weather ensued, to the annoy- ance of inhabitants of adjoining property, with a large accumula- tion of mud whenever the weather was wet.
The existing surface of the new carriage-way was excavated
36 CONCRETE ROADS
to an average depth of 7 in., except the portions adjoining exist- ing kerbs, which were cut out to a depth of 12 in.
At this stage the gas and water companies' men visited the site and satisfied themselves as to the necessity for any repairs to their mains and services before the new work was com- menced.
The concrete for the lower bed consisted of three parts of local ballast to the following specification : 1 part of material passing through a 1-in. screen and retained on ^-in. ; 1 part of material passing through a f-in. screen and retained on a I -in. ; 1 part of material passing through a |-in. screen and retained on a 22 screen.
To this was added 1 part sand all through ^ in. screen, and 1 part Portland cement, complying with British Standard Specification for slow-setting cement.
The top-course concrete was 1| in. in thickness, and consisted of one part best granite chippings graded from dust to -| in. One part sand all through ^ in. screen, and one part Portland cement.
The concrete was mixed by hand to a plastic consistency, and special attention was given to the placing of the top course, which throughout the entire job was carried along simultaneously with the putting in of the lower bed or base.
Transverse expansion joints were made in the concrete every 40 ft., and longitudinal expansion joints in the concrete alongside the kerbs. These were provided for before the concrete was laid by placing £-in, by 7-in. wrought boards of convenient lengths and slightly greased with a hard lubricating grease ; the boards were withdrawn when the concrete had set sufficiently to allow their being removed without the arrises being destroyed, and the expansion joints were filled flush with the finished surface of the concrete with commercial soft pitch.
As soon as the lower course was finished, and while the material ^as still plastic, the reinforcement was placed upon it and slightly pressed into it, the sheets of fabric being overlapped 4 in. at the sides. While the reinforcement covered the whole area between the expansion joints, in no case did it extend across them.
As the top-course concrete was laid the surface was immediately struck off by means of a template resting on one kerb, and one longitudinal screed, the template being moved over the surface with a combined longitudinal and transverse motion. Any excess pf material accumulating in front of the template was uniformly
IN THE UNITED KINGDOM— PROVINCIAL
37
FIGS. 25 and 26. — Views showing road construction at Tilbury.
>urse of
40
CONCRETE ROADS
FIG. 27. — Road in course of construction, Tilbury.
FIG. 28. — View of finished road, Tilbury.
IN THE UNITED KINGDOM— PROVINCIAL 41
distributed over the surface of the new road except when near the expansion joints, when the excess material was removed.
When the concrete had set sufficiently for a man to walk upon its surface without in any way disturbing it, it was fenced in and kept free from all traffic for twenty-one days, and the sur- face was well watered by means of a watering can for the first ten days and nights.
At each end of the new roadway a double row of 4-in. granite setts on Portland cement concrete, 6 in. in thickness, was laid to effect the junctions with adjoining surfaces.
Although owing to the increase in transport work at the docks the roadway has had to bear a continuously increasing traffic, the road after over a year's wear is as when laid down. The repairs and maintenance have been nil, in the summer there is a com- plete freedom from dust, in the winter an absence of mud, and a very agreeable running surface is provided for vehicular traffic.
The cost of the complete work, including granite, ballast, cement , reinforcement, and granite setts at junctions with adjoining roads, was IDs. 2^..'. per sq. yard.
Latest Report. — Mr. S. A. Hill-Willis, reporting on this road in November, 1920, stated that since the road was constructed in 1917 it has been traversed by all types of heavy traffic in and out of the Docks, and he is in every way satisfied with this trial length, so much so that contracts have now been placed by the Tilbury Urban District Council for 6£ miles of similar roadway in the place of tar-macadam. A 50-ton Parsons trench excavator recently passed over this road ; the rear wheels of the excavator were shod with heavy steel studs, but in spite o^ the great weight of the machine no injury was caused to the surface.
Hampshire
Southampton Docks. — This road was laid down at Southampton Docks in the summer of 1917. It is 342 ft. long, 25 ft. wide, and 6 in. thick, and has no paths or kerbs. It is level longitudin- ally, but has a transverse camber of 4 in. (about ^ in. per foot). The greater part is straight, but at one end it has a curve of about 100 yils. radius. It approaches one of the most important quays, where vessels up to 20,000 tons are berthed, and consequently has to sustain a fairly heavy traffic of all kinds. The ground in this neighbourhood was reclaimed from the estuary some years
42
CONCRETE ROADS
ago, the filling consisting of broken chalk several feet in thickness and overlying the original river mud. The site of the road had, however, been in use for about twenty years, so that the ground was fairly well consolidated. Before the new concrete was laid down the road paving had consisted of water-bound ( macadam resting on about 1 ft. of hard core, which again rested on the chalk filling. The latter had settled so much that in places it was necessary to raise the road as much as a foot. This was effected by covering the old macadam with ashes, which were consolidated by watering and rolling with a 10-ton roller, the surface being finished off with a camber ready to receive the concrete. The
FIG. 29. — Reinforced concrete Dock Road, Southampton, for London and South-Western Railway.
new pavement was made with Portland cement, and sea gravel dredged from Langston harbour. As no machine mixer was available it was all turned by hand three times dry and three times wet to ensure good mixing. It was 6 in. thick in all, the lower 4 in. being mixed in the proportion of 1 to 6. and the upper 2 in. in the proportion of 1 to 3. For this upper layer, the gravel was all passed through a f-in. square mesh screen so as to avoid the possibility of the road surface being pitted by the splintering
IX THE UNITED KINGDOM— PROVINCIAL 43
of large pebbles. In the lower layer of the concrete, and 2 in. from its under surface, was placed one thickness of reinforcing fabric.
While carrying out the work it was fortunately possible to divert the traffic on to a temporary road. After rolling the base, the first operation was to lay down the fabric, which was weighted and kept from touching the base by 2-in. pebbles or pieces of brick here and there. On the curved part of the road the fabric was laid parallel to the straight part and sheared off at the. sides to suit the curve. Immediately before placing the concrete, which was of a moderately wet consistency . the base was w^ll watered.
A length of 12 ft. to 15 ft. only was started every day, so as to be certain of finishing the whole thickness before evening. This ensured the fine concrete on top being incorporated with the coarser concrete below. Each day's work was finished off against temporary timber templates fastened on pegs at the sides and ends, the sur- face being formed by working a straight-edge longitudinally backwards and forwards on the end templates. By this means a fairly smooth surface was obtained and no rendering or touching up was necessary. To prevent the possibility of the surface being spoilt by rain at night, it was covered for twenty-four hours with a tarpaulin sheet, which was supported so that it did not touch the green concrete. After a length had been completed, the next was omitted for a while, and the alternate length concreted. Xo attempt was made to form any sort of expansion joint, the concrete being simply shovelled up against the older concrete face. The work occupied five weeks ; it was then left for another five weeks — viz., till October 9, 1917. when the traffic was turned on to it. As soon as weather conditions permitted (which was in November, 1917), the whole of the surface was served with a coat of hot tar, and dusted over with coarse sand.
Latest Report.— In November, 1920, Mr. F. E. Wentworth- Sheilds reported that the road has stood the traffic exceedingly well, and although, of course, a slight crack is visible at the joint of each day's work, there is no sign of deterioration here or elsewhere. What little wear there is is very even, so that there are no pot-holes or malformations of a sort likely to become intensified by further traffic. The surface is not slippery, and the road has given general satisfaction, and is still in excellent con- dition.
44 CONCRETE ROADS
Kent
On the Main London- Dover Road. — In the autumn and winter of 1914-1915 a trial length of concrete road 300 yds. in length was laid near Gravesend. During the time of its construction the weather conditions were most unfavourable, and as it was on a section of the highway from which the traffic could not easily be diverted, it became necessary to make one-half of the length of the road at a time. The original specification provided that the concrete should be of a 6 : 1 proportion throughout, that is to say, one part of cement to six of aggregate, including sand — certainly not a rich concrete. That portion of the road laid in this manner was, after its completion, tar dressed, probably before the con- crete was properly set. Heavy traffic was put upon it in its early days, and, in consequence, partial disintegration ensued. On the other side, where a bed of 4| in. of 6 to 1 had been put in with a metal mesh reinforcement above it, the authorities consented to a richer concrete being used for the surface, and this consisted of 1£ in. of 3 to 1.
This road was opened for traffic on March 15, 1915.
Nearly six years have elapsed since its construction, and the section last-mentioned, which has never been tar-sprayed or coated with any bituminous material, is still as good as when it was first used, except for a few slight abrasions where the transverse joints were put in.
The good condition of this part of the road has on more than one occasion been referred to by Mr. H. T. Chapman, the County Surveyor of Kent.
Latest Report. — At the Institute of Municipal and County Engineers in July, 191 9, Mr. H. T. Chapman said that the portion which was topped with 3 to 1 concrete was practically as good as when laid, and there were no signs of disintegration or cracks, except at the expansion joints, and we may further add that he is of opinion that the description given above still holds good in 1920.
Monmouthshire
The Main Road from Newport to Cardiff. — The main Newport to Cardiff road is probably one of the most heavily trafficked roads in South Wales. This road, although specially treated, had never been quite satisfactory, the poor subsoil being to some extent
IX THE UNITED KINGDOM-^PRO VINCI AL 45
FIG. 30. — A general view of the road.
FIG. 31. — A closer view of the good portion which has proved so satisfactory.
ROAD NEAR GRAVESEND.
48
1 CONCRETE ROADS
FIG. 32. — A detailed view of one of the joints in the good portion of the road, in order to demonstrate the undesirability of these.
I
FIG. 33. — A close view of the surface of one of the bays of good concrete, which shows how level this remains after well over 5 years' wear. The half of the road which was laid 6:1 is in the background, and the con- trast between the two halves is very noticeable in the photograph.
ROAD NEAR GRAVESEND.
IN THE UNITED KINGDOM— PROVINCIAL 49
the reason : so that it was thought that, all things considered, the position would give an excellent test of the possibilities of a reinforced concrete road.
Owing to the absolute necessity of keeping the road open to traffic, the length was treated in two portions. The width of the road between kerb lines was from 24 ft. to 26 ft., and as the width of the reinforcement was 7 ft., a 14 ft. width for the length of 300 ft. was dealt with first, thus leaving the remaining width open to the traffic.
The following specification was adopted : —
•'The thickness generally to be 6 in., laid in one course, with the reinforcement placed about 2 in. above the bottom of the concrete. The concrete to consist of one and a half of 2-in. local limestone, one and a half of 1-in. stone, one and a half of coarse sand to one part of cement. Transverse joints not to be provided, but a longitudinal joint to be formed along the whole length between the two portions of the road as laid. A strip of thin tarred felting to be placed against the finished portion as the work of laying the remaining portion proceeded ; thus the two lengths would be absolutely independent of each other. Where the concrete butts the kerb a clay joint of about f in. to be made on both sides. At the end of the day's work an additional strip of reinforcement 3 ft. wide to be built into the last portion of the day's work about 2 in. below the top of the concrete, leaving 18 in. of the 3-ft. width projecting, in order to help the bond with the next day's work. When completed the road to be allowed to harden for at least three weeks before opening to traffic, the surface being treated with tar and grit at the end of this period."
After the work of scarifying and removing the old macadam surface had been carried out to the required depth, the founda- tion, which was not any too good, was* well rolled by a 12-ton roller and made up in a few sunken places with hard, dry filling.
Laying of Concrete. — The work of laying the concrete was car- ried out exactly as specified, but it was found difficult to do this economically owing to the somewhat confined space caused through the necessity of keeping the one part of the road free for traffic.
Before spreading the concrete the foundation was saturated
50 CONCRETE ROADS
with water in order that none should be drawn away from the con- crete when placed into position, and while being spread the con- crete was tamped down by shovel and rammer.
The surface was obtained by means of a shaped floater or tem- plate 2 in. thick, 6 in. wide, and of a length sufficient to reach across the portion laid. This was operated by two men, one at each end, who gripped the handles provided for the purpose, and tamped along the fresh surface until the ends of the floater rested upon boards placed at the sides at the required level.
No other treatment was given to the surface, and the results obtained are considered to be very satisfactory.
As regards the mixing of the concrete, great care was taken that the proportions as specified were adhered to with each batch. A gauge-box ^ cu. yd. capacity, with strips placed at half depth, allowed the easy gauging of the 1| of large stone, 1£ of 1-in. stone, 1£ of sand, and the one part of cement ; the whole was mixed by hand, and only sufficient water added to make the mass into just a plastic state.
Each portion of the road when completed was allowed to stand at least three weeks before being opened to traffic, and during that time the surface was covered with fine sand to a depth of 1-in., and continually kept damp with water. Immediately before opening to traffic the surface was brushed clean and allowed to dry thoroughly before being covered with tar brushed in by hand and gritted.
Previous to this, the concrete surface was carefully inspected, and gave the appearance of being in excellent condition.
Weight of Traffic. — As with all new constructions, it is the practical test which counts. This road has now been open for over 12 months, and has during that time, especially owing to the railway strike, carried excessive traffic. Two days after the opening of the first portion laid, a very heavy traction engine with three loaded trailer wagons, the whole weighing at least fifty tons, passed over it ; also, six days after, a huge piece of machinery which had to pass through the town during the night, owing to its size, the weight upon one axle being close upon twenty tons, was drawn over the new length of concrete road. Coupled with this, the continuous heavy and fully loaded motor-lorry traffic which used this road during the railway strike, it being the main trunk road into South Wales, has undoubtedly proved that this concrete road is well able to
IX THE UNITED KINGDOM— PROVINCIAL 51
carry any traffic which is likely to be brought upon it. Up to the present, the surface has the same appearance as when first opened.
Cost. — As regards the cost, this has been rather high.
The cost of labour and also the amount of material used are given, as it may be some guide to those contemplating this mode of construction.
Cost of removing existing macadam roadway and preparing for concrete. Length, 300 ft. ; average width, 24 ft., equals 800 sq. yds. ; average depth, 6 in. : —
£ s. d.
Labour 56 10 9
Horse hire 35 8 5
Roller (scarifying and rolling) . . . 8 15 0
Watching and lighting . . . . . . 13 10 0
Supervision (say) . . . . . . .500
Total . . £119 4 2
This works out at 3*. per super, yard for preparing only.
There were 206 loads of useful material removed from the road and 300 ft. run of 12-in. by 5-in. stone channelling — for which a credit of £71 10s. is placed to the job.
Cost of reinforced concrete work : —
£ a. d. Horse hire .......
Labour .......
Watching, lighting and fuel
2-in. stone (73 tons 10 cwt. 3 qr. at 12s.) .
1-in. stone (69 tons 2 cwt. 2 qr. at 12s. 3d.) .
Gravel and sand (86 tons 5 cwt. 1 qr. at 12s.) .
Cement (42 tons 14 cwt. 1 qr. at 74s. 9d.)
Use of timber for staging, etc.
B.R.C. fabric . . . . . .
Incidentals .......
Tar
Supervision (say) ......
Total . . .£675 3 10
For the 800 sq. yds. 6 in. thick laid this gives a cost per super, yard of nearly 16s. lid.
52 CONCRETE ROADS
Taking the inclusive cost of the whole work and giving credit for the salvaged materials : —
Cost of preparation Cost of concrete work
Credit material
£ s. d. . 119 4 2 . 675 3 10
Net total
794 8 0 . 71 10 0
£722 18 0
or per super, yard, nearly 185. Id.
This is a high figure, but irrespective of what has been said above, there is no doubt that with better working facilities and more extensive work the cost would be considerablv reduced.
FIG. 34. — The main road, Newport to Cardiff.
Latest Report. — This road was laid under the supervision of Mr. Ivor F. Shellard, A.M.Inst.C.E., and Mr. H. Tremelling, M.Inst.C.E. The present Borough Engineer reported in November, 1920, that " the road is still standing in good condition, the only cause for anxiety being the longitudinal joint in the centre of the road, which is being worn down rather badly.'
54
CONCRETE ROADS
I
FTOS. 35 and 36. — Brecon and Abergavenny Road, in course of con- struction and partially completed.
IN THE UNITED KINGDOM— PROVINCIAL 55
Brecon and Abergavenny Main Road. — Work was commenced on this road at a point near the Brecon boundary in September, 1919, under the supervision of Mr. S. A. Bennett, A.M.I.C.E., the County Surveyor, one-half width being laid at a time. After about 100 yds. had been laid this portion was fenced off for twenty-eight days, after which the traffic wras turned on to it while the other half of the road was being constructed.
No longitudinal joint was made in the concrete, but a double layer of the reinforcing fabric about 18 ins. wide was laid at the centre of the road where the two halves met. Expansion joints were provided, but instead of being placed at right angles to the direction of the road, these were laid diagonally at intervals, and were filled with bituminous material.
The concrete, which is 6 in. in thickness, was laid in one course" and consisted of crushed furnace slag, graded from 2 in. to \ in., sharp freshwater sand, and Portland cement, in the proportion of 4£ slag, l£ sand and 1 cement.
Before being opened to traffic the surface was tarred and spread with a |-in. coating of granite chippings.
On account of the water-logged subsoil, diagonal cross drains were laid in the road, with 4-in. pipes, open jointed, the trenches being filled in with 6-in. broken slag. These cross drains are connected to a 6-in. longitudinal drain under the footpath, the drainage water being discharged into watercourses.
The width of the roadway is 20 f t . , and the length so far completed is about 800 yards.
The nature of the traffic over the road is both heavy and con- tinuous, and consists of heavy steam tractors with trailers, commercial motor lorries, and a frequent omnibus service, in addition to the ordinary local traffic. Prior to the concrete being laid, the road was constructed with most of the known pro- prietary materials, but on account of the soft nature of the subsoil it became almost impassable on account of corrugations and depressions.
Latest Report. — The County Surveyor, reporting on the condi- tion of the road in November, 1920, says: "So far the concrete road has been a complete success, having withstood the traffic, and showing no signs of disintegration or of any cracks."
56
CONCRETE ROADS
Northumberland
Longhoughton Road. — In May, 1920, the first reinforced concrete road in Northumberland was commenced by the Alnwick Rural District Council under the supervision of their Highway Surveyor, Mr. Nicholas Bean. The road, which begins at the Longhoughton railway station, is about a quarter of a mile in length and 24 ft. in width. With a gradient of 1 in 18 this hill has always been a source of trouble to the authorities, since, being the main outlet of the Northumberland whinstone quarries, it has to bear very heavy traffic, consisting mainly of steam wagons carrying loads of five tons of stone between the quarries and the railway, and has always had a tendency to "creep."
The concrete, which is 9 in. thick, was laid on a bottom of whinstone setts and consists of 2| parts of Northumberland whinstone chippings graded from 1 J in. to | in., and H parts of f-in. chippings and coarse whinstone grit, to 1 part of Portland cement. This aggregate is an ideal one for road work, being of a very hard, dense nature.
FIG. 37. — Longhoughton Road, Northumberland, showing road- making machine at work.
The Main North Road.— The first section of this road to be laid in reinforced concrete is situated between Wideopen, about five miles north of Newcastle, and Seaton Burn, a length of about one mile. The road is practically level, the only gradient being 1 in 30.
CONCRETE ROADS
FIG. 38. — Lower Bristol Road, Bath.
FIG. 39. — Bridge Street, Taunton, laid June, 1920. Surveyor, Mr. D. Edwaids. Length, 500 yds. ; width, 13 ft. 6 in. Traffic very heavy.
IN THE UNITED KINGDOM— i>ROVINCS AX* V^ $%
The concrete, which was laid on the top of the existing road, was mixed in the proportion of 3^ parts of crushed whinstone H in. to | in., and 1£ parts f in., mixed with coarse whinstone grit, to 1 part Portland cement.
The thickness of the concrete is 6 in., the reinforcement being placed about 2 in. from the under side.
The cross-fall is about 1 in. to the channel, and the surface is finished with tar paint and chippings.
As it was impossible entirely to close this main road, the con- creting was done in half -widths, each section being opened to traffic five weeks after completion. At the time of going to press one-half of the road has been finished and is said to be standing exceedingly well. It is the intention of the County Council, who have acquired some of the most up-to-date road-making plant, to layabout six miles of concrete road, and for this prepara- tions are being made. The work is being carried out under the direction of the County Surveyor, Mr. J. A. Bean, C.E., F.G.S.
Somerset
Lower Bristol Road, Bath. — In the first instance a length of 350 yds. of this road is being constructed in concrete, but upon com- pletion of this section a further length will probably be laid.
The centre of the road is occupied by a tramway track, and on either side of the road, which runs practically east and west, are high buildings which exclude sunshine, with the result that the road is hardly ever free from moisture.
The former road construction was hardwood paving, which had become in a deplorable condition, and, in view of the parti- cularly heavy traffic to which the road is subjected, it was felt by Mr. D. Edwards, A.M.I.C.E., the City Engineer and Surveyor, that the only solution was a concrete surface.
As the traffic could not be diverted and the width of the road in its narrowest part is 29 ft., the work was carried out in half widths.
The foundation is that of the original concrete, and so is well consolidated.
The thickness of the new road is 6 in., and the reinforcement was laid 2 in. above the bottom.
The aggregate consisted of Pennant stone, 1£ in. down to 1£ in. ; limestone, 1 \ in. down to 1 J in. ; fine stone chippings and
SJI^i'V".! « - tW CONCRETE ROADS
sand; and the proportions adopted were 1 part Portland cement, 1 part chippings, 1 part sand, and three parts stone. The amount of water used was from 1 £ to 2 gallons for every 6 cubic ft. of the materials taken separately, or, in other words, If to 2 gallons for every cubic foot of dry cement.
A portion of the road was laid with Pennant stone and a portion with limestone, with a view to comparison of results.
A batch mixer is used, and while being spread the concrete is tamped with shovel and rammer and finished off with a floater about 1 in. thick and 7 ft. long.
The finished work was covered with sand, which was watered daily. The road was not opened to traffic until one month after completion.
The surface was not treated in any way and thus this is a concrete road pure and simple.
Scotland
Canmore Street, Dunfermline. — Canmore Street is one of the few " level " streets found in the south side of a city where hills and steep gradients predominate. Connecting, as it does, with the centre of the town at its west end and with New Row at its east end — the latter being the principal route to the lower railway station, and very steep in that portion which lies between Canmore Street and High Street — it has to carry a very heavy traffic. During the summer of 1916 a motor-bus service was inaugurated between the city and the dockyard at Rosyth, with its starting point at the west end of Canmore Street. The roadway, wThich has an average width of 15 ft. 6 in. between the kerbs, was originally constructed of whinstone setts 7 in. deep, laid without a concrete foundation, and soon gave way under the bus traffic, so much so that within a very few months it became dangerous. The then Burgh Engineer, Mr. P. C. Smith, submitted two schemes to the Town Council : one to lift the setts, lay a concrete foundation, and relay the setts, grouting the same with pitch ; and the other to discard the setts and lay the roadway with 6 in. of concrete reinforced with steel wire and surface sprayed with tar and chipped. The latter was adopted.
The old setts having been removed and the surface brought to the proper contour and level, 2 in. of concrete was laid down and on this was spread the reinforcement. Two widths were required to cover the roadway, and an overlap, averaging 8 in.,
IN THE UNITED KINGDOMS-SCOTLAND.
FIG. 40. — Road during construction, Canmore Street, Dunfermline.
FIG. 41. — View of finished road, Canmore Street, Dunfermline.
IN THE UNITED KINGDOM— SCOTLAND 63
was allowed ; on top of this another 2 in. of concrete of the same proportions as the bottom layer was placed, and above this was laid the finishing coat, 2 in. thick. The work was so carried on that no layer was set before the other was superimposed upon it. • . •
The two bottom layers consisted of three parts 1 \ -in. machine - broken whinstone metal, two parts sharp sand, and one part cement, while the finishing coat was of two parts £to 1-in. whin-
FIG. 42. — Road prior to reconstruction, Canmore Street, Dunfermline.
stone metal chips, two parts granite |-in. to dust, and one part cement.
The surface contour was maintained by the putting in of pegs every 4 ft. along the kerb line and at the crown of the roadway ; on these were laid 1-in. laths from kerb to kerb, these being taken up as the work proceeded.
When the surface was about three -quarters set it was gone over lightly with a bass broom, thus securing a "key" for the tar spray ; it was thereafter covered over with fine sand which was kept moist for seven days and removed at the end of fourteen days.
On the work being completed, the surface — with the exception
64 CONCRETE ROADS
of 12 in. at the sides, which was finished smooth — was tar-sprayed and chipped with f to £-in. whinstone chips. No expansion joints were put in transversely, but along both kerbs were laid J-in. white pine boards the depth of the concrete. It was intended to remove these and fill the caviiy with pitch, but wet weather interfered and the wood was left in.
The cost of the work, which included the removal of the old setts, excavation, filling trenches for gas, water, etc., with 6 to 1 concrete, the concrete in the roadway, the fabric and the wood slips along kerbs, was 105. 4d. per super, yard, and the tar-spraying l%d. per super, yard.
Latest Report. — When the road was last inspected by the Burgh Engineer in September, 1919, it was found by him to be in as good a condition as on the day it was laid. He further reports that the only maintenance necessary between October, 1916, and the date of his leaving Dunfermline in 1919, was an annual tar- spraying and chipping, which was carried out at an expense of less than £5 per annum.
During the first year the road had to carry a heavy motor- bus traffic, which was suspended in 1917. But apart from this the road continued to bear a very heavy general traffic, including that of traction engines, with no apparent detriment to the surface. Mr. Smith states that from the experience gained in Canmore Street, Dunfermline, he is quite prepared, should occa- sion arise, to recommend the adoption of a similar construction for roads of a like nature. He is satisfied that where the surface is kept well covered with a coating of tar and chips, such a road will last for many years and will repay the time and cost expended upon it by a greatly reduced cost in annual maintenance.
The above report is borne out by the present Burgh Engineer. Mr. R. Muir Morton, who, writing in November, 1920, stated that ': the condition of the road to-day is very satisfactory, and, beyond requiring a new coat of tar, which it will receive in the spring, no fault can be found with the surface of the road. The work as it now stands is satisfactory and it is not anticipated that any extraordinary expense will have to be incurred thereon for a very considerable time."
Edinburgh
Blackwood Crescent. — That concrete roads are not the novelty which is often supposed is shown by the fact that the concrete
CONCRETE ROADS
FIGS. 43 and 44. — Views showing the road at Glengormly, Belfast, during
construction.
IN THE UNITED KINGDOM— IRELAND 67
carriage-way of Blackwood Crescent, Edinburgh, 441 feet long and 33 feet wide, was laid in July, 1873.
The construction was a 4-inch base of 2-inch broken stone, rolled, and a 5-inch coat of 1^-inch whinstone grouted with 1| parts of fine riddled sea gravel and 1 part Portland cement, well beaten down. No reinforcement was used, and the road has never been surfaced with any other material.
The city road surveyor, Mr. James Sims, reporting on this road on November 16, 1920, states that the surface is still in fair condition and, what is very remarkable, the total cost of main- tenance has been but £40 since the road was laid over forty-seven years ago.
Gillespie Crescent, Edinburgh, was laid about the same period and by a somewhat similar method.
Ireland
Glengonnly, Belfast, Antrim. — In August, 1915, a short length of rein- forced concrete road (48 yds.) was laid in the Belfast Rural District about four miles outside the boundary of the borough of Belfast. This was one of three experimental lengths on a portion of the Antrim main road where maintenance has always proved to be difficult and expensive on account of the boggy nature of the subsoil.
The width of the carriage way is 30 ft., and there is a footpath 6 ft. wide on the north-east side of the road, as well as a grass verge of about the same width on the south west side.
The specification adopted for the work was the one used for the Kent experimental length, with the exception that the con- crete, instead of having a uniform thickness of 6 in., was made 7 £ in. thick at the middle of the road, reducing to 6 in. at the sides. The road was laid in half widths, and each half width in 10-yd. lengths.
After the foundation bed had been prepared a 2 -in. layer of concrete was laid, and on this the reinforcement was placed longi- tudinally, with 4-in. overlap where the separate sheets joined. On account of the sheets overlapping, the reinforcement did not come quite to the edge of the 30-ft. width of the concrete, but the width outside the reinforcement was given an extra thickness of 3 in. underneath, being 9 in. thick for a width of 12 in. The
68 CONCRETE ROADS
upper layer of concrete was laid immediately upon the fabric and carefully tamped to bring it to the specified thickness, when the surface was finished off by men who used contour boards, which ensured that the surface had the proper form and cross -fall. The concrete surface was then covered with a 2 -in. layer of damp sand until the concrete had thoroughly set, and an interval of fifteen days was allowed to elapse before traffic was permitted on the new surface. The other half of the road was dealt with in the same way, and when the full width of the concrete had set and was thoroughly dry, the surface was tar-sprayed.
A traffic census on the Antrim Road near the Sandy Knowes cross-roads, where this length was laid, gave a total of 416 tons per day.
Latest Report, November, 1920. — Mr. D. Megaw, A.M.Inst.C.E., the County Surveyor, states that the length is at present in very fair order and there has been very little expenditure on it since it was laid, except the cost of tar-spraying each year : the road is subject to heavy traffic.
CHAPTER III
CONCRETE ROADS IN INDUSTRIAL WORKS AND MILITARY CAMPS
The Port of London Authority. — The system of reinforced concrete roads introduced and developed by the Port of London Authority presents many features of interest.
The road slabs are 9 in. to 10 in. thick, including a top wearing crust of 2 in.
The method of reinforcement, designed and patented by Mr. J. H. Walker, Assoc.M.Inst.C.E., of the Port Authority, was the outcome of the difficulty foreseen in laying a satisfactory concrete road upon the particularly soft ground of which the land in the vicinity of the docks is composed. The reinforcement provides for top and bottom layers of reinforcing bars combined and inter- locked with zigzag diagonal tension members in such a manner as to form a rigid mattress to which any additional bars may be attached as required (see illustration).
The steel is delivered direct to the site from the rolling mills in coils of ^ in. diameter wire and straight lengths of \ in. or ^ in. bars. The men quickly and economically bend and assemble the bars on rough benches, which latter are moved forward as the road progresses.
Very careful consideration was given to the question of rein- forcement. The reasons for adopting such a type of double reinforcement, with its accompanying great advantage of pro- viding steel diagonal members to counteract the shear or diagonal tension stresses, were as follows : —
(a) Economy.
(6) To provide two layers of reinforcement to meet the flexure
and contra-flexure stresses in the slab imposed by the
heavy rolling traffic, (c) To eliminate the necessity for providing objectionable
expansion joints and to prevent the concrete from devel- 69
70 CONCRETE ROADS
oping contraction cracks due to variations in temperature and amount of moisture in the concrete. The surface of the roadway being exposed to great variations in diurnal weather conditions necessitates steel reinforce-
FIG. 46. — Pyramidal interlocked reinforcement for roads, rafts, floors, etc., as used for Port of London Authority roads.
ment near the surface of the concrete, whilst, due to seasonal changes, a bottom layer of steel is also required. The pyramidal diagonal bars being anchored in the bottom layer of concrete also perform a very important
IN INDUSTRIAL WORKS AND MILITARY CAMPS 71
FIG. 46. — Reinforced concrete road in course of construction, showing reinforcement and the road-laying machine covered with canvas.
FIG. 47. — Finished view of road for the Port of London Authority at the Royal Victoria Docks.
74
CONCRETE ROADS
FIG. 48. — Reinforced concrete road at the works of Messrs. Joseph Baker, Sons & Perkins, Willesden Junction.
FIG. 49. — Reinforced concrete road at the works of Messrs. Joseph Baker, Sons & Perkins, showing the truck lines.
IN INDUSTRIAL WORKS AND MILITARY CAMPS 75
function in providing for any possible contraction of the concrete by spreading this contraction over innumer- able and practically invisible hair cracks.
(d) To provide a simple, cheap and practicable way of readily assembling the steel, and to ensure that the reinforce- ment, when laid, shall be in its correct position in the concrete, and also to provide a framework to which any additional bars can be readily attached when required over trenches or other exceptionally weak places. This system of constructing concrete roads was installed in the Royal Victoria Docks in the winter of 1917-18, and has ful- filled all expectations.
The proportions of the concrete, the methods of mixing, and construction of the road may shortly be described as follows : —
The lower 7 in. consists of 6 of Thames ballast to 1 of Portland cement, the top or wearing crust of 2£ of f-in. broken shingle, and 1J of sand to 1 of Portland cement.
The construction of the road was as follows : After the road bed had been excavated and graded, the reinforcement was laid there- on, the bottom 2 in. of concrete was placed in position, and the reinforcement lifted through it, by hooked bars, so that it rested on the concrete. The remaining 5 in. of the bottom 7-in. coat was then deposited. The top 2-in. coat was afterwards placed in position, tamped and screeded by a specially constructed screed worked by two men, which brought the surface to the actual level and contour required.
A special feature in the making of these roads was the machine for fixing, laying and screeding the concrete, which is briefly described in Chapter VI, page 165.
Messrs. J. Baker, Sons & Perkins, Willesden Junction.— A con- crete road was laid down at the works of Messrs. Joseph Baker, Sons & Perkins, engineers, Willesden Junction, under the super- intendence of Mr. S. W. Moscrip, the engineer.
Having studied the concrete roads of America and of this country, and examined the question in all its bearings, Mr. VIos- crip was satisfied that a concrete road was calculated to meet more satisfactorily than any other the demands made upon it by the heavy traffic which a road of this description has to carry ; the company therefore decided to give this method of construc- tion a trial.
76 CONCRETE ROADS
The foundation consisted of a mixture of clinker and ballast, well rolled and consolidated. The kerbing, which was laid first, is 1 ft. in depth, and is battered on both sides, being 6 in. wide at the top and 9 in. at the bottom. The concrete for the road it- self is 6 in. in thickness, and was laid in two courses, a lower course of 4 in., consisting of a mixture of one part Portland cement and five parts coarse material, and an upper layer of 2 in., consisting of one part Portland cement, one part sand, and two parts pea shingle, graded up to f in. diameter. The reinforcement consists of steel mesh. Adopting the principle to which, where reinforce- ment is used, recent experiments seem to point as being sound, no expansion joints were provided. The concrete was laid in alternate bays, and the material in the intervening spaces was laid close up to the concrete already in position. The surface was worked over by a trammel, shaped to the camber of the road, and was afterwards finished with a wooden float. When the concrete was sufficiently hard, the road was covered to a depth of about 2 in. with ashes, which were kept constantly moist, and allowed to remain for three or four weeks.
The road so far constructed is about 200 yds. in length and 24 ft. wide, and the result is satisfactory in every way. The sur- face is even, but not smooth, and presents a " dead " face which affords an excellent grip for horses and motor vehicles, and enables each to work up to its maximum power ; and although some two or three hundred tons of traffic pass over the road daily, there is in it neither crack nor flaw. Indeed, so satisfied is the engineer with the result of this experiment, that the company has in contemplation the construction of concrete roadways throughout the whole of its yards.
Latest Report. — Mr. S. Moscrip, the company's engineer, writing in November, 1920, states : " The road has been in use now just over three years and has cost nothing for maintenance or repairs. When the concrete was thoroughly dry we gave it a good coat of tar and sand and this has not worn off yet. Heavy loads up to 13 tons have been over the road in motor, steam and horse wagons.
" Messrs. Joseph Baker, Sons & Perkins are thoroughly satis- fied with this kind of road construction and will certainly use it in future extensions of their works."
Empire Paper Mills, Greenhithe, Kent.— This road forms the approach to the Empire Paper Mills, Limited, at Greenhithe, and was
IN INDUSTRIAL WORKS AND MILITARY CAMPS 77
laid in the spring of 1918. The length which has been concreted is about 800 ft., and the width of the road is 18 ft. between the kerbs. Concrete kerbing, 6 in. thick, was first moulded in situ, the mixture used being 3 of sand to 1 of cement. No reinforce- ment was used for this kerbing, but to allow for expansion joints were formed with deal strips £ in. thick, spaced every 12 ft. The concrete of the road was 6 in. in thickness, and con- sisted of a bottom 4 in. of 6 : 1 mixture, and a finishing surface 2 in. thick of 3 : 1. It was reinforced throughout with metal mesh, placed as nearly as possible 3 in. above the bottom — i.e., in the centre of the concrete. In order to reduce the number of joints (which are a source of weakness in concrete roads), each day's work was done continuously in one bay, and sufficient space was left between one day's work and the next to allow of the intervening bay being put in afterwards when those on each side were set. One thickness of tarred paper was placed against the ends of the completed bays before the intervening bay was filled in. The reinforcement was placed so that it stopped 2 in. from the end of each bay, and also 2 in. from the kerbing on each side, in order to ensure that it was protected by concrete from any risk of corrosion.
The number of vehicles passing over the road is not very great, but they are of all classes, including large motor lorries and steel- shod steam wagons. The illustration Fig. 50 shows this road after completion.
The whole road is on a gradient from one end to the other, but the gradient varies throughout its length. A cross-fall to both kerbs of 1 in 50 was provided.
Latest Reports, November, 1920. — -According to a report from the chief engineer of the above Company, Mr. D. T. Maclvor, and a later report by an independent observer, the road has been in use two years and is in as good condition as when first opened.
The method adopted for constructing this road, viz., by alter- nate bays, has quite justified itself, and has demonstrated that it is both unnecessary and undesirable to provide " expansion " joints in a reinforced concrete road.
It is understood that the Empire Paper Mills Company is highly pleased with this road, as, prior to its construction, great trouble and expense had been experienced in keeping up the macadam roadway, whereas the concrete road has cost nothing for upkeep, and is not affected by the state of the weather.
78 CONCRETE ROADS
A Factory at Southampton. — Fig. 51 shows a concrete road laid down at an important factory at Southampton. The road runs the whole length of the main buildings, some 2.500 ft. in all.
During the construction of the factory, which was a Govern- ment rolling mills, a hard core roadway had been formed approxi- mately on the same lines as the new concrete road, for which a good foundation had thus been prepared. Preparatory to starting work on the concrete road, the top of the hard core was picked over> screened, levelled and rolled. Concrete kerbs which had previously been cast in moulds were then laid on a concrete bed on either side of the new road, and served as forms for the concrete.
The roadway itself is 10 ft. wide between the kerbs, with double width passing-place, and consists of 6 : 1 cement concrete 10 in. thick, laid direct on the hard core referred to. No reinforcement of any kind was used, but the concrete was deposited in alternate sections 10 ft. 8 in. in length and the full width of the road. Upon this was laid a surface coat, 2 in. in thickness, consisting of granolithic paving. When these sections had set, the inter- vening portions were laid in a similar manner.
The traffic is of the heaviest and consists of motor wagons up to 10 and 12 tons in weight with broad flanged metal wheels.
The Portsea Island Gas Works, Portsmouth. — The Portsea Island Gas Light Company early in 1919 decided to lay a reinforced concrete roadway in Green Lane, a public thoroughfare for the mainten- ance of which the Company is responsible. The road, which carries a fair amount of heavy traffic, including tractors, steam wagons and motor lorries, was originally of water-bound macadam but this had been repaired and patched many times, and its con- dition was very bad ; a trial length in reinforced concrete was therefore recommended. The eastern half of the road, extending from the Gas Works entrance to the railway crossing, was put down in concrete, the remaining half, over which the same amount of traffic passes, being laid in water-bound macadam, in order to obtain comparative results. The concrete portion measures 725 ft. in length and 22 ft. in width between the kerbs.
Manholes were provided where necessary at the crown of the road, and gulleys were placed on both sides bedded in Portland cement concrete foundations.
Work was commenced on the site in June, 1919, and as it was
IN INDUSTRIAL WORKS AND MILITARY 0? AMPS':
FIG. 50. — Concrete road, Empire Paper Mills, Greenhithe.
FIG. 51. — A concrete road at a factory in Southampton.
IN INDUSTRIAL WORKS AND MILITARY CAMPS 81
fortunately possible to divert the traffic, the whole of the road was scarified to a depth sufficient to form a new bed, all surplus material being screened and the recovered metal carted away for vise on the second half of the road. A good solid foundation was ensured by filling in, watering and ramming any soft places in the bed; the latter being finally finished off to the required camber.
On the bed was laid the reinforcement — a metal mesh — a lap of 4 in. being arranged at the junction of each width, and a lap of 12 in. where one length ended and another began.
The aggregate employed was shingle dredged from Langs ton Harbour, in the vicinity of the Works. This was mixed with Portland cement in the proportion of 6 : 1 for the lower course of 4 in., and 3 : 1 for the wearing coat, the shingle for the latter all passing a f in. screen.
On depositing the concrete the reinforcing fabric was lifted and well shaken, and the concrete rammed to a depth of 2 in. below the reinforcement, the position of which was thus uniformly 2 in. from the under surface of the slab. Great care was taken that the upper 2 in. of fine concrete should be laid before the lower layer had set, and the work was finished off each evening at a straight edge placed transversely across the road. At the end of each day's work a strip of reinforcing fabric some 3 ft. wide was so laid across the road as to bond the two days' work together, half the width being left projecting.
The formation of the correct camber was effected by the use of two parallel screeds, placed one on each side of the road, and a template faced with hoop -iron, which was dragged backwards and forwards along the screeds after the laying of the concrete in each section. This gave a very good surface.
Good progress was made by the above method, the average rate of completion being about 30 ft. run per working day.
As the concrete was laid and the surface finished the work was protected from the sun by means of corrugated iron supported on poles. This temporary roof was moved daily to follow the work, and was replaced by a layer of wet sand, which was kept well wetted for three to four weeks after laying. Fig. 53 shows the sub-grade in the foreground, the roll of reinforcing fabric, the template and the corrugated iron protection.
When the concrete had thoroughly matured, the sand was removed, and finally a coat of hot dehydrated tar applied, the whole being dusted over with coarse sand.
82
CONCRETE ROADS
The road was opened for traffic six weeks after laying the last batch of concrete, or twelve weeks after commencing the work. The result has been considered very satisfactory, and up to the present has been an entire success. A photograph of the completed road is shown in Fig. 55.
In cost the concrete compares very favourably with the macadam road, and a very large saving in maintenance charges is anticipated.
Benefiting by their experience with this trial length of road, the company has since put down other concrete roads of greater length inside the Works. The method of laying these roads and their general construction are very similar to those of the trial length, but one or two modifications have been introduced.
In the first place the new roads are formed with concrete kerbs instead of stone, which forms the kerbing in the trial length.
ff+infot-c/'ng fabric' SECTION Of
FIG. 52. — Section through roads and border, Portsea Island Gas Works.
The layer of reinforcing fabric will project under the kerb and for a distance of 6 in. beyond its outer edge, where the concrete is formed into a step. This, it is thought, will reduce the stress on the kerb, and, as an additional safeguard, a further strip of reinforcing fabric 1 ft. 6 in. long has been laid through the body of the kerb, as shown in Fig. 52.
The question of camber has required some attention. Many concrete roads are laid with very little camber, 1 in 50 being often specified for this purpose. Doubtless this will allow water to run off provided the road can be kept reasonably clean, but a gas- works yard is usually so muddy as to render the road leading therefrom very needful of attention in this respect. A greater camber was, therefore, given to the trial road — some 4 in. on the total width of 22 ft., or 1 in 33, and this camber has been adhered to in the new roads.
The work was carried out to the specification and drawings of
IN INDUSTRIAL WORKS AND MILITARY CAMPS 83
FIGS. 53 and 54. — Method of laying concrete in Green Lane, Portsea Island, Portsmouth.
IN INDUSTRIAL WORKS AND MILITARY CAMPS 85
FIG. 55. — View of completed trial road at Portsea Gas Works.
Mr. T. Carmichael, the Gas Company's engineer and manager, and, we understand, has resulted in remarkably fine thoroughfares.
Chisledon. — An interesting development of the use of concrete for roads during the WTar was the making of a number of camp roads, and the illustration, Fig. 59, shows a camp road at Chisledon, about five miles from Swindon, where some concrete roads were constructed during the War. Altogether there are about two miles of these roads. The surface formation of the roads is reinforced concrete, 6 in. thick. The roads comprise different sections, one being 700 ft. long and 20 ft. wide. It was originally intended that the concrete should be covered with as- phalt or similar material, but eventually it was decided to leave the concrete surface as it was. Another road was 15 ft. in width. The concrete mix was 5£ to 1. The reinforcement was in the form of electrically welded steel wire placed about 2 in. from the under side of the concrete.
Loch Boon. — This road, which was laid in July, 1917, is about 700 yds. long and 16 ft. wide. It leads down to the loch from a road which runs parallel to the side of the lake but some dis- tance from it. The latter road is of macadam, and in some cases had been filled in several feet in thickness, but was still subsiding,
86 CONCRETE ROADS
and it was for this reason that it was decided to try reinforced concrete for the road down to the lake. The ground is boggy, but was drained by a system of field drains and ditches. The road was laid directly on top of the grass, which was fairly level, and any small hollows were filled up with stones, but there was no pitching and no rolling. It was understood at the time that the road was entirely experimental, and nobody expected it to carry the heavy traffic without showing some defects, although it was hoped that it would be better than the macadam road. The result has exceeded all expectations, as the road has carried all the traffic in connection with dismantling the camp at the Loch Doon Aerial Gunnery School and does not show the slightest defect. The surface is coated with tar spray and granite chips. The concrete, which is reinforced, is 7 in. to 9 in. thick. London, Brighton and South Coast Railway Goods Yard, East Croydon. — These roads, two in number, have been laid in the sidings which are used mainly for the discharge of coal, with the result that the traffic is of a very heavy order and comprises vehicles of all descriptions up to heavy steam wagons.
The base of the new road was prepared by scouring off to the required depth the top surface of the old road and consolidating to shape with a 10-ton roller.
Before concreting, test blocks were made and were broken at 7 and 28 days, the results being found to be satisfactory.
The thickness of the concrete is 6 inches, and the proportions adopted were 1 : 2 : 4, the larger aggregate being beach shingle obtained from Newhaven Harbour.
The reinforcing mesh was laid 2 inches from the under surface of the slab.
After the concrete had been laid, the surface screeded and the material allowed to set, the road was covered with sand which was kept wet for, approximately, three weeks, at the end of which period the sand was removed, and the surface allowed thoroughly to dry. It was then covered with a thin layer of tar and fine granite chippings.
Fig. 57 shows the sub-grade prepared to receive the concrete, and Fig. 58 is a view of the finished road.
The work was carried out under the superintendence of Mr. J. Petrie, O.B.E., the district engineer.
The first of these roads was opened on 24th June, 1 920, and the second on 29th September, 1920.
IX INDUSTRIAL WORKS AND
'CAMPS 87
CONCRETE ROADS
FIGS. 57 and 58. — Goods yard, East Croydon.
IX INDUSTRIAL WORKS AND
??:<: «1
FIG. 59. — Concrete road at Chisledon Camp.
PIG. 60. — A road at Swindon Works for the Great Western Railway Company (laid partly in 1916 and partly in 1919).
CONCRETE ROADS
FIG. 61. — Road at Messrs. Harland & Wolff's Shipyards, Belfast. Laid during 1919-20. Length laid up to November, 1920, about 2,000 ft. ; width varying from 18 ft. to 30 ft. Traffic: heavy shipyard traffic.
FIG. 62. — Hamilton Road, Belfast — laid for the Belfast Harbour Commissioners. Engineer, Mr. F, S, Gilbert, M.Inst.C.E.
IN INDUSTRIAL WORKS AND
FIGS. 63 and 64.— Road at Purfleet, at the works of Messrs. Jurgens Ltd. Engineer, Mr. E. H. Simons. Laid in April, 1920. Length, 840 ft. ; width, 18 ft. Traffic : heavy factory traffic,
WORKS AND MILITARY CAMPS
FIG. 65.— Road for Messrs. Lewis & Tylor, Ltd., Cardiff, laid May, 1920, Length, 164 ft. ; width, 16 ft. Traffic : Motor lorries.
FIG 66.— Colliery road for the Powell Duffryn Steam Coal Co., Ltd.. Tredegar. Engineer, Mr. W. J. Jones. Laid in April, 1920. Length, 240yds. by 13 ft. 6 ins. wide. Traffic: Very heavy motor lorries. Present condition leaves nothing to be desired.
CHAPTER IV CONCRETE ROADS IN OTHER COUNTRIES
New Zealand
PASSING now to the use of concrete for roads outside the United Kingdom, the experience gained in New Zealand calls for attention, and the following information is based on a paper read by Mr. Walter E. Bush, M.Inst.C.E., City Engineer, Auckland, before the Roads and Transport Congress held in London in November, 1919.
He stated his " belief in the future of concrete paving for climates like that obtaining in Auckland, especially as motor traction would tend more and more to replace horse traction in the future, and in respect to a number of streets he gave alternative estimates for paving such streets in compressed asphalt, wood block, stone setts and concrete. It was not, however, until the latter end of 1915 that the City Council authorized him to put down the first cement concrete pavement in the city, although cement concrete founda- tions had been put under all paved streets.
" The measure of success met with in the first street has led to its increasing use, and practically all streets that have since been per- manently paved have been carried out in cement concrete.
"By March, 1919, some 35,000 yds. in all had been completed, 14,000 yds. were in hand, and an additional 135,000 yds. had been authorized."
The following are some short particulars regarding three of the streets laid in Auckland, according to information furnished by Mr. Bush in his paper at the above-mentioned Congress : —
Little Queen Street. — This street is 423 ft. in length, and lying almost due north and south, thus exposing it to the sun's rays for the middle part of the day, which means that in summer-time the surface temperature is often as high as 120° F., and may sometimes exceed that. Its mean elevation is 9 ft. above sea level, and it
99
100 CONCRETE ROADS
serves the back or cart entrances of a number of warehouses and works to and from which the traffic is of the heaviest description, both two and three-horse lorries and also motor-trucks being used, carrying the largest loads that the very flat grades on the water front make possible, and it is also subjected to much turning and twisting traffic from the fact that many of the ware- houses have cart docks, and practically all unloading is done by backing the lorries and trucks either into such cart docks or against the kerb.
The street was prepared for paving by scarifying the water - bound macadam, excavating to the required depth and preparing and rolling the sub-grade to the required camber to receive a uniform thickness of 8 in. of pavement, with a fall from the crown to the channel of approximately 1 in 36.
Two-coat work was adopted, the lower six inches of 7 to 1 concrete and the upper two inches of 3 to 1 . The 7 to 1 concrete consisted of five parts of clean beach shingle having a fair propor- tion of sand, two parts of broken basalt between 1 in. and 2^ in. gauge, and one part of Portland cement, while the 3 to 1 concrete consisted of 2*25 parts of beach shingle, 0*75 parts of f in. gauge basalt chippings and one part of cement. The top 2 in. was laid immediately after the lower 6 in. had been roughly brought to its proper shape, and while it was quite greeh, in order to ensure that the whole 8 in. was practically homogeneous.
The surface was brought to a proper camber by a straight timber template shod with steel, operated transversely to the longitudinal axis of the street, from the centre to the channel, on screeds of angle iron fixed to bars in the ground, after which it was steel trowelled till it presented a wet, even surface ; after setting had commenced it was lightly broomed to remove glazing of any portion of the surface, and when setting had taken place the concrete was covered with bags and kept wet for eight or nine days.
It being midsummer, only three weeks were allowed before the road was opened to traffic, and after nine months it was treated with Calif ornian asphalt, brushed on hot and dressed with screened beach shingle.
Prior to the application of the asphalt dressing the surface showed slight signs of wear in one or two places where the shingle had not been so good as in the remaining portions, a fact which emphasizes the necessity of using only the best qualities of aggre-
IN OTHER COUNTRIES • . . : 1Q1
gate available in this class of pavement. This road was completed in February, 1916.
Durham Street. — This was done with one-coat work 7 in. thick of 5 to 1 concrete, the traffic conditions not being so severe as in the preceding road, and it was left untreated and has stood quite satisfactorily since its completion in October, 1916.
Park Road forms a portion of Auckland's busiest traffic outlet, and lies immediately eastward of the important reinforced concrete viaduct known as Graf ton Bridge, which is surfaced with com- pressed Neuchatel asphalt. The road was completed in July, 1917.
It carries mixed traffic, most of which is fast travelling, and includes heavy petrol motor-wagons and chars-a-bancs, but no motor-buses similar to those so common in London, the number of vehicles counted being over 2,000 per day of ten hours.
The work was done in two halves to prevent stoppage of the traffic, and was much delayed by difficulty in obtaining shingle owing to bad weather, and this resulted in some shingle being used which was not absolutely first class, and also in the street being opened up for traffic sooner than was advisable. This caused the engineer to cease using shingle for aggregate and to substitute broken basalt and sharp sand.
The change was mado during the progress of the Park Road job, which was a one-coat pavement of 5 to 1 concrete, 8 in. thick, and the bays done with the basalt and sand aggregate showed enough superiority to the rest of the work to justify the alteration made.
With the exception of a short length of the basalt and sand concrete, the whole surface was treated with a dressing similar to that used on Little Queen Street.
In all the streets paved since 1917 the paving has been one- coat work of concrete composed of clean basalt chippings and screenings varying from IJ-in. gauge to "fines" mixed with 25 per cent, of sharp beach sand free from shell and gauged with Portland cement in the proportion of 5 of aggregate to 1 of cement, but prior to the concrete being laid the sub -grade is sprinkled with 2 1 -in. clean basalt road metal as a measure of economy. In all cases the sub-grade is carefully prepared and rolled solid, and steel rod reinforcement is laid transversely over trenches likely to cause trouble by subsidence.
102
CONCRETE ROADS
The cost per sq. yard, of pavement only, for the above thre6 streets worked out at 10s. and 9s. respectively.
In addition to the roads above described, it is interesting to note the other works done to the end of 1919, as scheduled in the accompanying table.
|
Kame of Street. |
Length in Feet. |
Area in Square Yards. |
Thick- ness in Inches. |
Cost per Sq. Yd., Pave- ment only. |
Date of Comple- tion. |
Remarks. |
|
Market Roads . |
640 |
1,340 |
7 |
8/- |
Mar., 1918 |
Untreated. |
|
Exchange Lane . |
140 |
155 |
4 |
• 5/3 |
Dec., 1917 |
Untreated. |
|
Quay Street Ex- |
530 |
3,828 |
8 |
9/- |
Mar., 1918 |
Untreated. |
|
tension |
Intersected |
|||||
|
by railway |
||||||
|
sidings. |
||||||
|
King's Wharf Rd. |
605 |
2,351 |
8 |
9/- |
May, 1918 |
Untreated. |
|
Intersected |
||||||
|
by railway |
||||||
|
sidings. |
||||||
|
Beach Road |
1,896 |
12,801 |
8 |
— |
May, 1919 |
Double-track |
|
tramway. |
||||||
|
Anzac Avenue . |
2,347 |
9,909 |
8 |
— |
— |
Under con- |
|
struction in |
||||||
|
March, |
||||||
|
1919. |
||||||
|
Symonds Street. |
3,100 |
13,427 |
'8 |
— |
Sept., 1919 |
Double-track |
|
tramway. |
Total length, 10,453 ft. Total area, 49,372 sq. yds.
In addition to the above an area of over 2,000 sq. yds. in Pitt Street, on which trial lengths of proprietary bituminous pavement had been laid on a 6-in. concrete foundation and had failed, was surfaced on the old concrete foundation with a rich concrete (3 to 1), half of the area being an average thickness of 3 in. and the remainder 3£ in. This was only completed in March. 1919.
Note. — The prices paid for labour and materials were as fol- lows : Labourers 10s. Id., finishers and machine men lls. Id. per day of 8 hours ; cement delivered 50s. per ton ; basalt chips and screenings 10s. 3d., basalt road metal, 2^-in. gauge, 9s. 3d., and sand 10s. lid. per cu. yard.
Dealing with the question of concrete mixing, Mr. Bush expresses himself strongly in favour of machine mixing.
Regarding joints he adopted the use of tarred paper, folded
IN OTHER COUNTRIES;
1D3
FIG. 67. — Western Motor Track, St. Kilda Road, Melbourne.
FIG. 68.— New South Head, WooMahra, Sydney.
lOu
CONCRETE ROADS
IN OTHER COUNTRIES 107
to form two thicknesses, and these were placed approximately 56 ft. apart, the length of bay laid being 14 ft., and four bays a convenient length for a joint.
Out of 35,000 yds. laid, of which only 5,216 had been coated, not a single crack had been discovered between the bays, and only in Little Queen Street and Park Road, in which shingle concrete was used, were there any noticeable signs of wear. The tarred paper joints and those formed by the junction of two bays are coated with asphalt and fine shingle.
Australia
In Australia some experiments in reinforced concrete road con- struction have been carried out at Melbourne and Sydney in the suburban areas, notably on the St. Kilda Road, Melbourne, and the New South Head Road, Sydney.
St. Kilda Road, Melbourne (West side). — An extended, and what may, so far, be called a satisfactory test with a reinforced con- crete road has been made by the South Melbourne City Council on the west side of St. Kilda Road on a section within the council's jurisdiction. It was carried out under the supervision of Mr. A. E. Aughtie, M.Inst.C.E., City Surveyor. Five different, but conjoint, sections of the road were laid with steel mesh reinforcement — longitudinal and transverse, and triangular — supplied by two different makers, and with plain concrete, in order that a comparative test might be made of their relative values. In March, 1914, one chain of road was experimented upon, 33 ft. being laid with plain concrete, and 33 ft. with con- crete and longitudinal and transverse steel mesh reinforcement. In June, 1915, 2£ chains of plain concrete road were put down ; at the same time half a chain of concrete road with triangular mesh reinforcement was laid. In March, 1916, half a chain of concrete road with longitudinal and transverse mesh reinforce- ment was constructed.
The reinforcement in the several instances mentioned was laid in concrete 6 in. thick, while the plain concrete road was 6-8 in. The concrete mixture for the various tests comprised four parts of blue stone screenings two parts of sand, and one of cement. The width of the road so treated is 24 ft., with 3 ft. of channelling on either side. The surface of the various sections was tar painted and sanded.
108 CONCRETE ROADS
Reporting on the test Mr. Aughtie said it had conclusively shown that there had been absolutely no wear on the surface, anql to all appearances it was as sound as on the day on which it had been laid. A number of transverse cracks, however, had appeared in the plain concrete road and at the junction of the reinforced road, but very few had shown themselves in the latter. Taking the reinforced sections as a whole, the cracks were of a very minor nature and the structure gave evidence of durability.
New South Head Road, Sydney.— Some time ago the Woollahra Council, Sydney, experimented with a section of the New South Head Road, near Mona Road, Darling Point. There is a founda- tion oi a depth of 6 in., consisting of concrete made in the following proportions : — >S cu. ft. of H-in. blue metal, 8 ft. of f-in. metal, or " shivers," 10 ft. of blue metal screenings, and 4 cu. ft. of cement. Over this layer of ^concrete is laid the reinforcement. Above this is the wearing course, which consists of a rich concrete mixture of two parts of blue metal screenings to one of cement. The length of road constructed was 160 ft., with expansion joints 20 ft. apart.
Canada
The Toronto-Hamilton Highway.— This is one of the most interest- ing examples of concrete road construction in Canada, and is thirty-five miles in length. The former Engineer of the Toronto- Hamilton Highway Commission, Mr. A. E. Wynn, has recently stated that this road represents the best and most modern practice in road building. For this reason we give some brief particulars of its construction, together with illustrations.
The road is a link of the Provincial Government's scheme for a system of main highways connecting the towns, and it carries more traffic than any other road in Canada.
Its construction was undertaken in the autumn of 1914.
The specifications adopted very closely followed those of Wayne County, Michigan, which is the pioneer district for concrete roads. All work was done by day labour under the supervision of the Commission's engineers.
The pavement itself had a standard width of 18 ft., with shoulders
IN OTHER COUNTRIES
109
FIG. 70. — The road before concreting.
FIG. 71. — View of finished road at Oakville. THE TORONTO-HAMILTON HIGHWAY.
IX OTHER COUNTRIES 111
3 ft. wide on each side composed of the natural earth, gravel or crushed stone.
The width was increased to meet local conditions, such as through towns and villages. It was 24 ft. wide for a few miles outside Toronto, and reached a maximum of 50 ft. wide through the town of Oakville.
Materials and Method of hatidling them. — Only tested cement of known quality was used. Before considering any stone for use an inspector visited the quarry, and all details as to the methods of handling, screening, output per day, etc., were recorded. A sample of 100 Ib. was carefully selected from different points in the quarry and shipped to the testing laboratory.
Here the following tests were made : —
(1) Resistance to wear — (2) Resistance to impact — (3) Specific gravity — (4) Absorption — (5) Weight — (6) Granulometric analysis —(7) Voids— (8) Cleanliness.
Most of the stone used was limestone or dolomite varying in size from 1£ in. down, and had to pass the above tests satis- factorily before being accepted.
All sands used were tested for cleanliness, grading and tensile strength, and from the result of these tests certain sands were decided upon to be used.
Every car-load of sand or stone was inspected before shipping, and samples were sent in periodically to the laboratory to be tested in order to be sure that they were up to specifications. On these tests, too, was based the exact mixture to be used with a certain aggregate.
The mixture adopted was nominally 1 cement, 1£ sand, 3 stone ; but this was checked up by the tests and was varied slightly to suit different aggregates. When there was any change in material the testing engineer gave to the field engineers the correct mixture to be used and the amount of water required for mixing.
At convenient points along the road material yards were built alongside the railway, about eight miles apart. Xew spurs were run into each yard. The cars of material were unloaded by a clamshell bucket into large wooden storage bins with hopper bottoms.
The material was then transported to any desired point along the road by means of a narrow-gauge temporary tramway ; the dump cars being loaded automatically from the storage bins,
112 CONCRETE ROADS
The track was laid on steel sleepers and bolted together in 20-ft. sections, so that each section could be easily and economically handled by two men.
The material was deposited along the road, behind the mixer, in such quantities that as concreting progressed and the mixer moved backwards there was always just sufficient material on hand, with no waste or shortage.
Each train load carried cement , sand and stone in the desired proportion, so that there was no delay in concreting due to in- sufficiency of one of the materials.
The sub grade consisted of the natural soil, mostly sand. It was rolled flat with a 10 -ton roller and thoroughly wetted down to prevent absorption of moisture from the concrete. Side forms for the concrete pavement were 6-in. iron channels, which were accurately lined up and staked in place by instrument for some distance ahead of concreting. Materials were mixed by half cu. yd. mechanical mixers, steam-driven.
Water was pumped from the nearest available supply. The amount of water used in mixing was accurately gauged by a meter fixed to the machine and was varied to suit different aggre- gates, but was kept constant for any particular aggregate. This correct proportioning of water is very essential in road work and is a point often overlooked. It ensures a uniform mixture and is an important point in preventing cracks.
The materials were mixed in the drum of the mixer for a specified time, and the concrete was then dumped out into a bucket which travelled along a 20-ft. boom, to be deposited where required.
Construction of Road. — The cross section of the road was a parabola, 6 in. thick at the sides and 8J in. at the crown, laid in one course. As the concrete was deposited it was levelled off by a template, handled by two men, and resting on the sido channel forms.
Following up were the cement finishers, who worked from a wooden bridge spanning the pavement. They floated up the surface with wooden trowels, just sufficiently to bring the moisture to the top.
No attempt was made to render the surface smooth, as a slight roughness gives a better foothold, and too much trowelling will bring the fine particles to the top, which would be liable to cause dust.
All pavement was laid in 35-ft. sections. Between each section
IX OTHER COUNTRIES 113
was an expansion joint about £ in. wide, consisting of prepared asphalted felt.
This felt was laid against the end form, which was set truly in line and vertical, and the concrete was carried up to it. complet- ing one section. Then concrete was laid the other side of the form, and after setting a short time the form was taken out and the space filled with concrete. To ensure the concrete being exactly the same height on either side of the joint, a special trowel was used with a groove to fit over the felt filler which projected above the pavement about £ in.
After concreting followed the " curing."
The day after the concrete was laid it was covered with 2 in. of dirt and was sprinkled with water daily for ten days.
After about four weeks the dirt was removed, the joint fillers
FIG. 72. — View of finished roacl, Toronto -Hamilton highway.
trimmed to within a quarter of an inch of the pavement surface, and the road opened to traffic.
At intervals during concreting l-cu.-ft. blocks were made and left along the road to cure in the same manner as the pavement. They were marked according to their location and were afterwards tested in the laboratory.
The pavement was not carried over culverts until after the fill had thoroughly subsided, and was always reinforced with wire fabric or ordinary fencing-wire, to prevent cracks.
I
114 CONCRETE ROADS
The pavement as a whole was not reinforced except over bad places in the sub grade.
Building the 3 -ft. shoulders was the last operation, the material employed being mostly that used for curing.
On the other hand, all culverts and bridges were built during the winter under the severe climatic conditions that exist in Canada. They were all constructed of reinforced concrete, the longest spans being 125 ft.
Concrete was laid in very low temperatures with no ill effect. The danger lies in using frozen material and in allowing the concrete to freeze before gaining its initial set.
Maintenance so far has been a small item and is easily covered by fines imposed upon motorists for speeding. The cracks are cleaned out and filled with tar, heated to about 225° F. Coarse dry sand is then sprinkled over, an excess of sand and tar being used, and the traffic is allowed to iron it out.
Traffic along the road has far exceeded all estimates.
CHAPTER V
THE GROWTH OF CONCRETE ROADS IN THE UNITED STATES
AMERICAN ROADS AND THEIR DEVELOPMENT UP TO 1920
AT the close of the year 1909. there were six miles of concrete road in all of the United States. At the close of 1919 there were 11,400 miles of concrete road. These mileage figures are based on the actual yardage built, and since different roads are constructed of different widths the usual road width of 18 ft. was used for the pur- pose in hand. So the growth from practically zero to a mileage that would span the continent from the Atlantic to the Pacific more than three times shows how the popularity of these roads has in- creased.
The study of the evolution of concrete roads cannot well be carried on without at the same time taking note of the develop- ment and use of .the automobile. In 1909 there were 127,731 cars in the United States, whilst at the end of 1919 a total of almost 8,000,000 was reached, with an annual production of nearly 2,000,000 cars. It will readily be seen that the develop- ment of concrete roads and that of the motor driven vehicle have been side by side. Carrying the motor-car figures a little further, it is found that in the United States there is one car for every fourteen persons, and automobile manufacturers expect production for 1920 to be greatly increased. Motor-cars demand a smooth, rigid road. It was not so with roads when the horse was the motive power. Horse-drawn travel compacts dirt and gravel roads, while motor traffic disrupts these same roads. The speed of trucks and automobiles is at least five times greater than that of the wagon and surrey,* likewise the cost of driving intricate and expensive motor vehicles is correspondingly more expensive on poor roads.
It is particularly interesting, as we bear in mind that concrete roads and automobiles have developed side by side, to notice another fact. Detroit, Michigan, is the centre of the automobile industry,
* A four-wheeled pleasure carriage (commonly two-seated), somewhat like a phaeton, but having a straight bottom.
115
116 CONCRETE ROADS
and Wayne County, which contains the city of Detroit, is generally recognized as the pioneer among counties throughout the entire United States as a builder of concrete highways. At this point it is fitting that recognition should be given to Mr. Edward N. Hines, who, as chairman of the Board of County Road Commission- ers of Wayne County, had the vision and foresight to anticipate the need for hard roads, and who by great personal initiative was able to convince voters and taxpayers that a comprehensive system of concrete roads connecting the principal points in the county should be built. At the outset considerable difficulty was experi- enced in determining the proper width and thickness of the pavement. It was a pioneering venture, and there were few rules or experiences by which to guide their actions.
Many of the first concrete roads were much narrower than those built since highway building experience has become more rounded. Eighteen feet is now considered the minimum as a practical width for country roads. This width gives an opportunity for trucks and automobiles to pass with a good margin of safety at reasonable speed, and in a large measure prevents road accidents.
The history of concrete roads, spanning as it does the short period of a decade, may properly be divided into three parts. First, pre- war construction, which commenced, as we have said, in 1909 and continued until America entered the World War. Second, the period of war construction, which took place from the date of the entry of the United States into the world conflict until the signing of the Armistice. The third period may be called the post-war period of construction, which began at the signing of the Armistice and continues until the present date.
The period of pre-war construction carries us largely through the experimental and educational stage of concrete road-building. From 1909 until 1911 actual construction was limited, and in those two years less than 300 miles of road were built. During 1912 and 1913 considerable stimulus was felt, and from 1914 until 1917 the construction of concrete roads throughout the United States was carried on at a rapid rate. When a graph of the mileage by years is plotted, the curve covering the last-named period becomes almost perpendicular. In the four years ending in 1917, 5,000 miles of 18-ft. concrete roads were built. People were buying cars. Farmers who at first had frowned upon self-propelled vehicles, and had regarded them as a whim of the idle rich, had come to find out that the car and the truck were valuable aids in carrying on their farming
GROWTH OF CONCRETE ROADS IN
FIG. 73. — A concrete road near Salt Lake City. (2 1 miles long.)
FIG. 74. — Morrison Road, between Denver and Morrison, Colorado. (About 1 mile long.)
FIG. 75. — Andrews Road, near Atlanta, Georgia. (6,000 ft. long.)
FIG. 76. — Churchland Road, Xorfolk County, Virginia. (Nearly 2 miles long.)
GROWTH OF CONCRETE ROADS IN UNITED STATES 121
operations. With the motor-car they could attend to more business than ever before, and with the truck they were able to take care of the increased business that came. Rural communities began to want concrete roads. Now the farmers became consistent supporters of concrete highways for their trucks and motor-cars.
Then came the entry of the United States into the World War. The mobilization of 4,000,000 men for arms and the mobilization of the remainder of the population for industrial work made labour unavailable for continued road construction. Moreover, had labour been available, material and transportation could not have been furnished, since it, too, was diverted to war work. The country at large had, as we have said, become educated to good roads, and now came severe tests that were to prove the soundness of its logic in asking for permanent roads. Particularly around army camps and the roads traversed by military trains pavements were put to the crucial test. Heavy pieces of artillery and endless trains of heavy trucks carrying war supplies rapidly wore down all pavements that were not of the highest class. Gravel and macadam roads failed rapidly. Many other types that .were considered fair under peace-time conditions gave way before the strain. It is interesting to observe that where the army engineers reconstructed these military roads they were usually built of concrete and successfully withstood the severe punishment that our military establishments imposed upon them. Reverting to the actual mileage constructed during the war period, we find that J,533 miles of concrete road were built in 1917 and 1,300 miles in 1918.
The situation, then, at the signing of the Armistice in November, 1918, was this : Before the war the popularity of the automobile had created a widespread sentiment for good roads, and the heavy punishment that roads received under war-time conditions proved that concrete roads were better able to stand the stress than other types.
After the war was over there was a strong, widespread sentiment throughout the United States to build roads. The various States and other road-building units gave large contracts, and in 1919 4,130 miles were built or contracts awarded. It was the premier year for road construction. With hardly an exception every State increased its mileage. The State of Illinois, which contains the city of Chicago, voted $60,000,000 worth of bonds to build State highways.
The same day that Illinois pledged itself to spend $60,000,000
122 CONCRETE ROADS
in improving its roads, the State of Pennsylvania voted a like amount. The State of Michigan, which, as we have pointed out, was a pioneer in road-building, voted $50,000,000 additional bonds in 1919. This money will be used in extending its road system. During the same year the State of California voted $40,000,000, Oregon $10,000,000, and Alabama $25,000,000, in road bonds. During the coming year Missouri will vote on the issuance of $60,000,000 worth of bonds, and Minnesota will vote on the issuance of $100,000,000 worth of bonds, to be used in improving the roads in the States named. This sentiment prevails in practically every quarter of the United States, and bond issues totalling high into the millions were passed, and all was in readiness for the greatest era of road building in the history of our own or any other nation. In 1920, $625, 000, 000 is available for road work, and the programme will yet, in all probability, be much enlarged. But conditions were such that the building had to be either curtailed or postponed. Labour is very costly and at the same time extremely scarce even at the high wage scale offered. Transportation facilities are to a large extent disorganized and overworked. Their equipment is not sufficient to take care of the present industrial needs of the country, and manufacturers of cement and dealers in road materials find themselves helpless to receive raw material or deliver finished products.
A sketch of the concrete road in the United States wo\ild not be complete without mentioning the roads built by the State of Cali- fornia. As Wayne County, Michigan, was the pioneer county in con- crete road-building, California stands out in bold relief as the first great State building an extensive mileage of concrete road. California builds her roads almost exclusively of concrete. In this State alone are almost 2,500 miles of roads made of concrete. At the close of 1919 there was a thirty mile stretch of concrete highway known as the " Ridge Route " in California opened to the public. The cost of this road was something like $1,200,000, and it was estimated by conservative State officials that with the heavy traffic that would pass over this road the total cost of building would be absorbed in less than 200 days by the saving in petrol, tyres and upkeep on the vehicles passing over it.
As has been suggested, the entire people of the United States are strongly in favour of good concrete roads. The term " concrete " has come to be accepted as the general word designating all that good roads should be. The Federal Government has made liberal
GROWTH OF CONCRETE ROADS IN UNITED STATES 123
appropriations to help to build roads where States and counties have properly applied and their project has been accepted. The Federal Government assists in building what is known as Federal Aid Pro- jects. The platforms of the political parties have paragraphs endors- ing the continuance of building good roads. There is no doubt that of the roads to be built concrete will be strongly represented. When conditions get back to normal, there is reason to believe that the United States will carry on continuously a programme of road building that will not stop until every important highway is paved, and the lanes leading into these main routes will, if not paved, at least be highly improved. It may truly be said that this is the era of concrete roads in the United States.
Fro. 77. — Coast Route, San Francisco to Los Angeles, California.
CHAPTER VI
MECHANICAL DEVICES FOR MAKING CONCRETE
ROADS
THE construction of concrete roads in an economical and efficient manner depends, to a very large extent, on the properly co-ordinated use of a number of mechanical devices. It is, of course, possible to make excellent concrete roads without the use of any machinery, but the time required and the cost of such a procedure are excessive. By the use of suitable machinery the drawbacks of hand labour are avoided, the large number of men with wheelbarrows and shovels are unnecessary, and a considerable amount of material as well as time is saved. Consequently, the use of suitable machinery not only reduces the cost of construction, but enables a much larger area of roadway to be laid in a given time.
The mechanical devices used for constructing concrete roads may be arranged in five groups : — •
1. Appliances used for preparing the road-bed.
2. Appliances used for preparing the concrete.
3. Appliances used in placing the concrete.
4. Appliances used in striking and tamping the concrete.
5. Appliances used in finishing the surface.
Appliances used for Preparing the Road-Bed
It is essential that the road-bed or foundation shall be properly prepared or the concreted surface will not be durable. Hence great care should be taken to ensure the bed being of the proper width, shape and solidity. This is best secured by digging out the surplus material by mechanical means, giving the bed the cor- rect curve or camber by means of a grading machine, and rolling or tamping the surface, if necessary, to increase its compactness.
Steam-shovels have long been used for quarrying and railway work, but their employment for road-making is comparatively new. They
124
MECHANICAL DEVICES FOR MAKING ROADS 125
have now been modified so as either to remove a relatively thin slice of material or to cut their way through a hill. When used for levelling a rough piece of country — as in working a wholly new road or in widening an existing one — steam-shovels are found to be much cheaper and quicker than hand-digging, and far less super- vision is required.
A British firm of steam-shovel manufacturers is Ruston and Hornsby, Ltd., Lincoln, whose No. 5 Excavator (Fig. 78), by reason of its remarkable mobility, wide range of move- ments, ease of control and general utility is particularly suitable for road-making. This excavator is capable of taking a maximum depth of cut of 20 ft. without breaking the top down by hand, and will also successfully deal with very shallow cuts for grading, With the standard bucket-arms this machine can excavate a trench to a depthof 6 ft., and, by the simple expedient of letting out the jib ties and fitting slightly longer bucket-arms, up to 12 ft. The minimum bottom width of cut with 1 to 1 slopes is 12 ft., and the maximum height of open bucket door from rail level 12 ft. 9 in., the maximum and minimum discharging centres being 22 ft. and 15 ft. respectively.
Small revolving steam-shovels have been in use in the United States for road-making with great success. The sizes which are most popular are equipped with dippers of £ or f cu. yds. capacity. Two such dippers full of material would com- pletely fill the ordinary tip wagon or cart, while three dippers would load a 2-yd. wagon or cart to its maximum capacity.
The shovels revolve through a full circle, permitting the ma- chine to dig or dump at any angle and enabling them to operate successfully in limited space. The latter feature is especially valuable when it is necessary to build one-half of a roadway while the other half is open for traffic. These steam-navvies will excavate any materials which can be penetrated by picks and shovels, and they are also valuable in handling properly blasted rock.
The shovels have capacities in ordinary roadwork varying from 15 to 60 cu. yds. per hour, depending on the depth of cut, class of material, and manner in which disposal of the material is organ- ized.
Traction wheels are generally used on this class of navvy, but any of them can be equipped with standard gauge car wheels, and on some of the shovels continuous tread traction can be substi-
126 CONCRETE ROADS
tuted where desirable. It must, however, be recognized that the use of any type of caterpillar traction, while it increases the speed of the shovel in operation, makes moving of the shovel from one job to another very much slower than is the case where ordinary traction wheels are used.
These shovels are sufficiently light to be used for ordinary street and road work without planking, although most of the traction wheels are so arranged that cleats can be attached when necessary.
Several of these machines, in addition to the customary fea- tures of steam-navvies, are equipped with special devices for use in shallow cuttings and for automatic levelling and grading work.
While these navvies are generally classed as " one man " machines, it is usually desirable to provide an assistant to take care of the firing of the boiler, keeping up the coal and water supply, and generally assisting in operation. One or two pit men are needed, depending on the type of machine, speed of the work, and the care which it is necessary to give in cleaning and levelling up.
It must be recognized that the output from these navvies depends almost altogether on the skill of the operator. A working speed of from two to three dippers per minute can be obtained by the average operator, although skilled men can obtain from four to five dippers per minute with the same shovel working under similar conditions.
Some navvies of the type mentioned above are the Erie Shovels, manufactured by the Ball Engine Company of Erie, Pennsylvania, and now sold in this country by Gaston Limited and by William Muirhead, Macdonald Wilson & Co. Ltd., the Thew Shovel, manufactured by the Thew Shovel Company, Lorain, Ohio, sold in this country by the Allied Machinery Company, Ltd., and the shovels manufactured by the Bucyrus Company of Milwaukee* Wisconsin, sold in England by Messrs. George F. West & Co.
Cranes and Grabs. — For lifting large quantities of loose materials, such as sand, aggregate and tipped earth, it is sometimes cheaper to use a crane and grab than a steam shovel.
A firm of crane and grab manufacturers in this country is Priestman Bros., Ltd., Hull, one of whose machines is shown in Fig. 79.
A modification of the Erie shovel in which a grab is used instead of a shovel is shown in Fig. 82. A similar crane and grab, made
MECHANICAL DEVICES FOR MAKING '
FIG. 78.— Huston & Hornsby No. 5 Excavator.
FIG. 79. A Priestman Grab.
FIG. 80. Erie Shovel.
CONCRETE ROADS
FIG. 81. — Crane and Grab.
FIG. 82. Erie Shovel with Grab.
FIG. 83. — Pipe Line Excavator.
MECHANICAL DEVICES FOR MAKING ROADS 131
by Pawling and Harnischfeger Co., Milwaukee, Wis., and obtain- able in this country from Gaston, Ltd., is shown in Fig. 81. This machine is a complete portable locomotive crane with a lifting capacity of 1 £ tons at 30 -ft. radius. It is driven by a petrol engine and can travel under its own power at a rate of 1 mile per hour.
Drag-line Excavators are chiefly used on sticky soils or for lifting loose materials, but they may also be employed for grading roads of which the material is not too hard. As shown in Fig. 84, this type of excavator has an inverted bucket or dipper suspended from the boom by a rope and, on reaching the ground, this bucket is dragged towards the machine till it reaches the limit of its journey ; it is then lifted, the whole crane is swung round and the contents of the bucket are discharged. By suitably regulating the suspen- sion and drag lines, the bucket may be made to dig itself into the ground to a convenient depth prior to its being drawn along and a cut up to 8 in. deep obtained. The caterpillar wheels are a special feature of the drag-line excavators made by Pawling and Harnischfeger Co.
Trench Excavators. — As their name implies, trench excavators are specially designed to make deep, but relatively narrow cuts, chiefly for pipes for water, sewage and gas, and electric conduits.
Standard trench excavators are manufactured in various sizes to cut trenches from 12 in. to 76 in. wide and in varying depths to a maximum of 20 ft. at a rate of 6 in. to 40 in. linear per minute, according to the nature of the ground and the size of the machine.
Trench excavators are commonly built in two classes, one being known as the wheel type, the other the ladder type exca- vator.
Wheel Type Trench Excavators are suitable for trenches not more than 7 ft. 6 in. deep. They consist essentially of a vertical wheel provided with a series of cutters around its circumference, the wheel being mounted on a strongly trussed steel frame which also carries the oil engine, hoist or conveyor for the excavated material and the oil tanks.
The excavator should be provided with a steering gear, so that either right or left-hand curved trenches of any radius may accur- ately be cut, and a grade-control or lifting device should also be provided, so that the trench is cut to the full depth and the bottom is left at any desired slope or grade. In the wheel excavator (Fig. 83) made by Pawling and Harnischfeger Co., the excavating
132 CONCRETE ROADS
wheels are of the open type, i.e., without an axle, and are arranged to obtain the maximum depth of trench with the minimum diameter of wheel.
Ladder Excavators are much more powerful and are capable of digging to a much greater depth than wheel excavators. The ladder excavator usually consists of two endless chains running over an adjustable boom, the chains carrying a series of toothed cutters and buckets. As the chain revolves these cutters penetrate the ground slightly, and the material thus excavated is carried upwards to be discharged as the bucket reaches the top of the boom on to a chute or conveyor, which in turn transports the excavated material to either side of the machine. It can be dumped into a pile for backfilling or direct into tip wagons or carts. Ladder excavators should have ample strength, since excavating deep, wide trenches for sewer and similar projects subjects them to constant heavy strains. Ladder excavators of this type are manufactured by Pawling & Harnischfeger, and sold through Gastoiis, Ltd. ; the Parsons trench excavators sold through the Allied Machinery Co., Ltd. ; the Bucyrus sold through Messrs. George F. West & Co. ; the Austin sold by the Austin Machinery Company.
Backfillers. — -Where openings are made in roadways it is always necessary to re-fill the trenches. This process — sometimes termed backfilling — is often done in an unsystematic and inefficient manner, and, consequently, is unnecessarily costly. Re-filling trenches can be accomplished economically by a mechanical backfiller such as is shown in Fig. 88, which consists of a scraper attached to a light motor-driven crane with a supplementary winding drum. The scraper is lifted and carried behind the pile of earth or other material ; it is then lowered and dragged across the hollow portion or ditch into which it discharges its contents, and is then ready to be lifted back preparatory to repeating the operation. Such a machine will re-fill a trench as rapidly as twenty-five to fifty men moving the material a distance of 15 ft. to 25 ft. The machine only requires one man for its operation. In the backfilling of trenches it is of great importance that the material should be thoroughly rammed or tamped, and although this operation has up till now been chiefly performed by hand, a machine for so tamping and trenching has been designed in America and is actually in use in this country.
MECHANICAL DEVICES FOR MAKltfGT *tok&fe
FIG. 84. — Drag Line Excavators.
FIG. 85. — Ladder Excavator.
FIG. 86. — Jubilee Wagons.
FIG. 87. — Hepburn Conveyor
Fro. 88.— Backfiller (Gaston).
FIG. 89. — Adams "Leaning Wheel" Grader. 136
MECHANICAL DEVICES FOR MAKING ROADS 137
Wagons. — The excavated material should, wherever possible, bo placed directly into wagons, those known as the Jubilee type (Fig. 86), supplied by the Ransome Machinery Co. (1920) Ltd., being very convenient. '; Trains " of six or more wagons are hauled away to the tip by a motor or locomotive.
Conveyors. — When circumstances do not permit the excavated material to be placed in wagons direct from the excavator, it should be conveyed on to one side of the road, well out of the way of the workmen by means of a portable conveyor. Several suit- able conveyors are on the market, the one shown in Fig. 87 and made by the Hepburn Conveyor Co., Wakefield, being very satis- factory.
Grading Machines. — Grading machines are used to ensure the foundation of the road having the correct inclination and camber. Xumerous machines for this purpose have been constructed in various sizes to be operated by horse or mechanical traction. In general they consist of a heavy frame mounted on four steel wheels, the frame carrying a long blade. The position of the blade is universally adjustable to any angle or depth, the useful work of the machine being performed as this blade is drawn for- ward along the work in such a way as to move the material from the centre of the road to the side, or vice versa. In some cases, larger type machines also are provided with scarifying attach- ments so that macadam roads can be loosened up and re-graded. Several successful machines are on the market, among these being the Adams " Leaning Wheel ;' grader ; the Austin Giant type ; and the Western Aurora type grader. Fig. No. 89 shows an Adams grader making a cut almost the entire length of the blade and delivering the earth just inside the left rear wheel.
Rollers and Tampers. — In order to consolidate the foundation of a road, especially those parts which have been made by ''fill- ing," rollers or tamping devices — operated by hand or power — • are employed.
Hand and Horse-Operated Rollers are only suitable for the lightest and smallest work. They are so well known as to need no descrip- tion here, especially as their use is rapidly diminishing.
Steam Rollers are invaluable where great pressure is required for compacting the foundation. They should be designed so as to
138 CONCRETE ROADS
secure the maximum pressure on the roller, whilst still retaining sufficient " weight " on the rear wheels to ensure satisfactory driving up steeply inclined gradients.
For road-making, a steam-roller should have sturdy construc- tion and ample boiler capacity, with the boilers and cylinders mounted so as to facilitate quick repairs.
The design should be as simple as possible, as such machines work continually under adverse conditions and frequently in Out-of-the-way places. In order that the roller may be stable, its centre of gravity should be low, yet there should be sufficient space above the ground to prevent the engine being damaged by obstacles which the roller has failed to crush or by the machine having to work on very irregular ground.
As steam-rollers are not required the whole of the time, it is convenient to attach a belt to the fly-wheel and from this to drive a crusher, screen or other machinery which can be operated at intervals.
Motor Rollers in all sizes have been in successful use for a great many years. They are manufactured in both the single and double cylinder types, and some of them can be run on paraffin, the advantages of the motor-rollers being that they can be operated by one man, that keeping them supplied with fuel is less costly, and that they do not require a constant supply of water.
Machines at present on the market are manufactured by Messrs. Barford & Perkins, Peterborough, and the Austin Manufacturing Company of Chicago.
Preparing the Concrete
The chief mechanical devices used in preparing the concrete are crushers for the coarse aggregate, sand washers, screens, measuring devices, appliances used for transporting the raw materials as well as the concrete " slop," mixers and engines for the supply of power. It is convenient to consider each of these separately.
Crushers should reduce the large lumps of stone or other material used for coarse aggregate so as to produce angular fragments of the required size. Machines which produce rounded pieces are useless for road-concrete. Jaw-crushers and gyratory crush- ers are the most satisfactory ; in the former the lumps are crushed between two plates, one of which moves towards and away from
^MECHANICAL DEVICES FOR MAKI^
FIG. 90. — Trench Tamper.
FIG. 91.— A Winget Crusher.
FIG. 92. — Concentric Cylinder Screen.
CONCRETE ROADS
Fia. 93. "Devil" Disintegrator,
FIG. 94.— C. E. V. Hall's Disintegrator.
MECHANICAL DEVICES FOR MAKING ROADS 143
the other, whilst in a gyratory crusher the material is broken by the toothed faces of two cones between which it falls. The crushing effect is obtained by a gyratory motion imparted to the cone by the special gearing. Stamping mills and crushing rolls are less effective, and edge-runner mills are quite unsuit- able.
Jaw Crushers. — Among the commonest of this type of crusher are the Blake-Marsden (made by H. R. Marsden, Ltd., Leeds) and that made by Messrs. Winget, Ltd. (Fig. 91).
One example of this type of mill is the Heclon crusher made by Hadfield, Ltd.
The crushers just described are suitable for coarse aggregate but not for sand, as they are not economical when used to grind a material to a fine powder.
Disintegrators or Cage Mills consist essentially of (a) a pair of cages revolving in opposite directions, the material being broken be- tween these cages and passing out between the bars, or (6) a ro- tating shaft carrying loosely pivoted hammer-bars which rotate like the spokes of a wheel and deliver a rapid series of blows on the material contained on a grate until the material is crushed small enough to pass through the grate. These disintegrators (with various minor improvements) are made by several firms. An illustration of the exterior of the " Devil " disintegrator made by the Hardy Patent Pick Co., Ltd., Sheffield, is shown in Fig. 93, and an illustration showing an interior view of another disin- tegrator made by C. E. V. Hall, Sheffield; is shown in Fig. 94.
Disintegrators are not suitable for grinding to a very fine pow- der, but are very efficient for reducing hard lumps in sand, and for producing a proportion of fine flour in the sand.
It is generally preferable to use crushers and disintegrators on the site of the raw material and not in the roadway, though where the latter course is preferred, the crushing machinery may be mounted on a stout truck and driven by a portable engine. Care should be taken, in selecting an engine for this purpose, to choose one which is not readily damaged by the great and sudden varia- tions in the power required. A little consideration will make it clear that each time a hard piece of stone undergoes the crushing process the pressure applied to it increases steadily until it exceeds the maximum resistance of the stone, when the latter yields
144 CONCRETE ROADS
suddenly and the pressure being just as suddenly relieved the engine will " race " badly until pulled up more or less suddenly by the next piece of stone. This jerkiness of action is largely inevitable ; it is much less serious in a steam-engine than in a gas, petrol or oil-engine or an electric motor. If one of the last four is used, it should be much more powerful than is strictly necessary in order that it may not be suddenly stopped, and pos- sibly damaged, by a stone of unusual hardness.
Where very finely powdered material is used, an entirely different type of crushing apparatus is required ; this cannot suitably be used on the site of a road, and such special material — which is seldom required — should therefore be bought ready for use.
Washers. — As the presence of some kinds of clay is detrimental to the setting and hardening properties of concrete, and as it is always desirable to wet both the fine aggregate and sand thoroughly before putting them in the mixer, it is convenient to wash them prior to use, though this process is often omitted on account of its cost. Such washing consists essentially in stirring up the material with a sufficiently large volume of flowing water to bring the clay and " dirt " into suspension and to carry it away. Wash- ing machines used for this purpose therefore consist of some form of container fitted with agitators and some means of carrying the sand forward in one direction, whilst the water, bearing away the clay, etc., flows in another.
A considerable number of types of washers are used in various industries, but they require adaptation before they can suitably be used for the fine aggregate and sand used for concrete.
As all types of washers necessarily require very large volumes of water, they cannot usually be employed on the site of a new road, but are preferably erected on the site where the fine aggregate or sand occurs or at some central site to which it is taken, treated and then delivered in a washed state to the road-makers.
The Baxter Ballast Washer and Grader, illustrated in Fig. 95, is, however, being used on the site by the Southwark Borough Council, London.
Screens are essential for the production of a properly graded aggre- gate, and failure to use them has, on several occasions, resulted in
MECHANICAL DEVICES FOR MAKING ROADS 145
the production of concrete of such low quality that its failure to withstand the strains put upon it was inevitable.
The coarse aggregate should bo passed through a series of steol cylinders, the perforations in which are arranged so as to form a [series of sieves or riddles through which the material passes consecutively, a portion of it being separated by each screen.
A commonly used device consists of a single cylinder, 6—14 ft. in length, the circumference of which is divided into four or more
FIG. 95. — Baxter's Ballast -washing and Grading Machine, fitted with petrol motor. The machine, which is taken from street to street as required and connected to the nearest hydrant, was used by the Borough Council of Southwark for washing and grading the material from the old macadam roads.
sections, each of which consists of a series of perforations of defin- ite size, the finest being at the entrance end of the cylinder. When an ungraded coarse aggregate is passed through such a cylinder, the smallest fragments pass out through the smallest perforations, the remainder travel forward as the cylinder revolves, pieces of increasingly larger size being separated until the largest " stones " fall out at the exit end of the cylinder and are returned to the crusher for further treatment. The chief objection to such an arrange- ment is that the separation or grading is very inefficient. The slope or inclination of the screening cylinder and the speed at
fc
146 CONCRETE ROADS
which it revolves impel the material much too rapidly through it, with the result that, instead of all the pieces of aggregate of any given size passing through the desired perforations, some of them are carried forward and pass through larger openings. Even when baffles are inserted in the cylinder the grading1 — though better — is far from satisfactory.
To avoid this serious objection, Messrs. Johnston and Chapman Co., U.S.A., supply a screen which consists of three or more con- centric cylinders (Fig. 92), arranged so that the outermost ones have the smaller perforations. By this means the largest pieces are separated first, and no pieces can pass to the next section of the screen unless they are of the proper size to do so. Such an arrangement has the further advantage of only allowing the smaller pieces to come into contact with the finer portion of the screen, so that these can be made of thinner metal and they are not so rapidly spoiled by wear and tear.
Rectangular screens are occasionally employed — chiefly for small quantities and for relatively crude grading. If properly arranged, however, a series of rectangular screens can be made to work with remarkable efficiency especially for the finer aggregates, and with little or no expenditure of power. Rectangular screens may be of two kinds, horizontal or inclined, the latter being usually more satisfactory and requiring less labour. An excellent type of inclined screen is the " Newaygo " screen made by Messrs. Sturtevant Engineering Co., Ltd., which consists of a sheet of perforated steel plate inclined at an angle of about 45 degrees and arranged so that it is vibrated by a number of hammers which rotate on shafts above the sieve and periodically strike raised projections on the sieve provided for the purpose, thus keeping the apparatus constantly in u state of vibration. The material is supplied to the uppermost end of the sieve by means of a screw conveyor, and as it falls down the incline the small particles pass through the perforated plate whilst the coarser ones run down either into a box below or on to a coarser screen. The vibration of the screen prevents the holes in the sieve becoming clogged, unless the material is very sticky.
In some cases, several screens of varying fineness are suspended one below another, so that the material passing through one sieve passes on to a finer one below it, and so on until the whole of the material is satisfactorily graded, when it may be mixed in the required proportions.
MECHANICAL DEVICES FOR MAKING ROADS 147
Elevators are particularly useful for lifting the road-materials from the ground level to trucks, etc., and where sufficiently large quantities are involved. Their use is much cheaper than that of hand-shovels. These elevators consist essentially of an end- less band or its equivalent, on which is mounted a series of slats or buckets which carry the material. If the height to which the material is to be lifted is not great, a plain band-conveyor will suffice, but for greater angles of elevation buckets are preferable.
A self-contained wagon loader, supplied by Messrs. Winget, Ltd. (Fig. 97), will fill a 3-ton lorry in twelve minutes. It is specially designed for filling trucks and wagons with sand, gravel, crushed stone and similar materials, and is driven by a 2^-h.p. petrol or benzol engine, or, if desired, by electric motor.
The belt-conveyor made by the Hepburn Conveyor Co., Ltd., Wakefield, shown in Fig. 87, is equally useful where an elevator of this type can be used.
The addition of two rotary discs (as in the loader supplied by the Allied Machinery Co.) (Fig. 96), converts a bucket elevator into a self-feeding machine and so greatly enhances its value in road-making. The two horizontal steel discs set close to the ground revolve inwards towards the conveyor.
Transporting the Materials. — The raw materials, consisting of stone or gravel, sand and cement, are usually brought to the roadway in motor-lorries, wagons or carts. Where the materials must be dumped in the roadway, these should preferably be of the self- tipping type, so as to reduce to a minimum the labour required in emptying them.
Among the large number of tipping wagons available the " Constable " Patent Side-Tipping Wagons (Fig. 100) of Messrs. Tuke & Bell, Ltd., may be mentioned. During the operation of tipping, an angle of 50 degrees is obtained, which is sufficient to eject any class of material. The door on the side of the body automatically remains in its normal position and out of the way of the material being tipped. The load is discharged in 90 seconds.
The material tipped on the side may be transported in wagons or carts ; or an automatic feeder and conveyor system, such as the Barber- Greene Loader (Fig. 96) may be employed for this pur* pose.
148 CONCRETE ROADS
It is convenient when reloading materials on the site to use wagons, carts or boxes which also act as measures.
It is of the greatest importance that the transporting, propor-
" tioning and distribution of the materials should be effected
systematically and with a minimum of labour, as it is easy,
through carelessness or absence of suitable appliances, to spend
a double amount of money on these portions of the work.
Keeping Aggregates Clean. — One of the essential but too often neglected features in constructing concrete roads is the. delivery of clean aggregate to the mixers. Engineers rightly insist on the use of clean stone, sand and cement ; therefore, wherever possible, the material should not be dumped on the sub-grade or on the side of the road, since in re-handling it to the mixer it is quite possible that a considerable amount of sub-grade or shoulder material may become mixed with the aggregate.
This may largely be avoided by combining the measuring and delivery of the stones, sand, etc., with the transportation of the material direct from the source of supply to the mixer. In most road jobs this can be accomplished by placing the material for a complete batch in specially constructed boxes or carts. These boxes or bodies can be built, or can be obtained from manufac- turers in several sizes; the material is automatically measured to ensure accurate proportions, and so that they can be easily dumped directly into the mixer or into the mixer loading skip.
In addition to ensuring the cleanliness of the material, this method of charging the mixer is usually much more economical than dumping the material on the grade ahead of the mixer, since it eliminates a double handling of all material.
A fixed measuring hopper is supplied with Ransome Mixers (supplied by the Ransome Machinery Co., Ltd., London). The hopper is of such dimensions that it contains the requisite quantity of aggregate to form the batch in each size of machine. The door is operated by a hand-lever. Every Ransome Mixer, un- less otherwise specified, is also despatched with a water-measuring tank attached.
Various mechanical measuring devices suitable for concrete road materials are on the market, though most contractors will find the divided wagon previously mentioned, or separate "boxes," quite satisfactory and free from great liability to error or serious
MECHANICAL DEVICES FOR MAKING ROADS 149
FIG. 96. — Barber-Greene Loader, supplied by the Allied Machinery Co., Ltd.
FIG. 97.— Winget Self-Contained Wagon Loader.
152
CONCRETE ROADS
FIG. 99. — Ransome Hand Mixer.
FIG. 98. — Ransome Elevator.
FIG. 100.— Constable Wagon.
MECHANICAL DEVICES FOR MAKING ROADS 153
misuse ; they do not require any power, such as is always the case with mechanical measurers.
The Measurement of Water is most satisfactorily effected by means of a tank of the required capacity which is fixed at a suitable height above the mixer, and is so arranged that a definite quan- tity of water — neither more nor less than is required — is delivered on opening the tap. An ordinary water-saver syphon tank with a ball- valve, controlling the feed is excellent for the purpose, as it delivers the water with the utmost rapidity and can be refilled automatically from a larger tank without any trouble. Water- measuring tanks fitted with taps are often troublesome, and the delivery of the water is usually too slow.
The water tank used in connection with a concrete mixer should be of ample size, yet not excessively large. For the size of mixer most suitable for road work, a tank delivering 17 or 18 gallons is satisfactory.
Elevators. — The cement, aggregate and sand must usually be lifted from the ground level to a short distance above the inlet of the mixers. If the material is transported by means of a conveyor no further arrangement for raising it is needed, but in other cases some form of elevator is desirable. Such elevators may conveni- ently form a part of the mixing plant. The use of an elevator reduces the cost of charging the mixer and, under certain condi- tions, increases the output by reducing the time required to charge the mixer. The advantage is very marked when the mixer is located at a considerable elevation above the level at which the aggregate, etc., is delivered.
Many elevators which have been in use in the past are primitive and crude in design and arrangement, but several more recent designs are quite satisfactory. Among the latter is the Ransome Elevator (Fig. 98), which consists of an elevating skip of rectangular form to avoid undesirable clogging when discharging its contents. The skip is controlled by a single lever, by the use of which all operations of lifting, discharging, lowering and steadying during its descent are controlled.
Mixers. — The machines used for mixing concrete are arranged in two classes, according as they are operated by hand or mechanical power.
Hand-Mixers are chiefly useful for small repairs, as they are very
154 CONCRETE ROADS
portable and essentially "one-man" machines. A convenient machine (Fig. 99) for this purpose is made by the Ransome Ma- chinery Co., Ltd. ; it has a capacity of about 2 cu. ft. and an output of 2-2^ cu. yds. per hour. The mixer is of such dimensions that a standard navvy barrow can be readily placed beneath the drum in order to receive the batch when discharged.
In the " Smith Hand mixer " (Fig. 10 1 ) made by Messrs. Stothert and Pitt, Ltd., the mixed concrete is discharged on to a board placed ready to receive it, or into wheelbarrows. In the latter case it is advisable to remove the wheels, placing the machine on timbers sufficiently high to allow wheelbarrows to pass underneath and receive the charge. When desired, the mixer can be placed so as to discharge its contents into a trench, and being portable can readily be moved along as the work progresses, discharging each batch exactly where required. Two men are required to drive this mixer, which has a capacity of 3-3| cu. ft. of unmixed material, and an hourly output of 2£-3| cu. yds. of concrete. Power -driven mixers have replaced the hand -driven machines for all except the smallest jobs, as they not only mix a larger quantity of concrete at a time with greater certainty, but they can be arranged to discharge it precisely at that part of the road where it is required. Power-driven concrete mixers are of two chief types, (a) continuous and (6) batch mixers. Con- tinuous mixers are seldom satisfactory for road-making, as the conditions are not usually favourable ; batch mixers should, therefore, be used in most, if not all, cases. In a batch mixer, definite measured quantities of all the ingredients are placed in a hopper or skip provided for the purpose, and this quantity of material—termed the batch— is introduced into the mixer, in which is added a definite and proper quantity of water. When the process of thoroughly incorporating the ingredients is com- plete the mixed material is then completely discharged from the mixer, which is ready to receive the next measured batch which has, meanwhile, been prepared in the hopper or skip previously mentioned.
Mixers which are especially adapted for road-making have been developed to a very satisfactory and economical point. The introduction of the material into the mixing drum usually requires its elevation to a considerable height ; therefore, most of the satisfactory road mixers are equipped with some type of power- operated elevator. They are also equipped with means for
MECHANICAL DEVICES FOR
FIG. 101.— Smith Hand Mixer.
1083 FIG. 102.— Ransome Self-Contained Mixer.
158
. ^CONCRETE ROADS
FIG. 103. — Ransome Mixer.
FIG. 104. — Victoria Mixer.
FIG. 105. — Rex Mixer.
FIG. 106.— Winget Mixer. FIG. 107.— Winget Chain Spades.
MECHANICAL DEVICES FOR MAKING ROADS 159
mechanically distributing the concrete after the mixing is com- pleted. This is accomplished by means of a pivoted chute into which the material is dumped from the mixing drum. A wider range of distribution can be effected by means of a boom and bucket arrangement. These booms are maae in varying lengths to 25 ft. A bucket attached to an endless rope is drawn in towards the mouth of the mixing drum and receives its charge; the wind- ing gear is then reversed and the bucket drawn out along the boom to the point of discharge, where an automatic trip arrange- ment causes the bottom doors of the bucket to drop open. As the boom is pivoted so that it will swing through 1 80 degrees, a very large area can be covered. Since road work requires that the mixer should be moved frequently as the work progresses, it has been found advisable on most paving mixers to arrange for power traction derived from the engine which operates the mixing drum. Certain types of mixers are also arranged so that from the same source power is derived for steering the machine during the moves.
Mixers of the above type can be supplied by the Ransome Machinery Co. Ltd. (Figs. 102 and 103), by Messrs. Stothert &Pitt, Ltd. (Figs. 104 and 108), Messrs. Gaston,Ltd. (Figs. 105 and 109), and by the Allied Machinery Co., Ltd. (Figs. 113 and 114).
The "Winget" Mixer, which has a capacity of 3 cubic feet, has been fitted with special mixing arms (in place of the chain spades illustrated in Figs. 106 and 107) for wet concrete, and is as suitable for road work as for site concrete and Drench concreting.
Laying the Concrete
The mechanical devices employed in laying the concrete on the roadway include : (i) The forms or shuttering boards which pre- vent the material from flowing outside the prescribed limits and also determine the thickness of the layer of concrete ; (ii) distribu- ting devices used for applying the concrete to the road surface ; (in) the devices used for spreading the concrete.
The forms or shuttering boards are held in position by clamps of any convenient pattern. As wooden forms easily warp, they can only be used a limited number of times and are more costly than appears at first sight, it is usually more economical in every way to use steel forms, such as the Blaw forms, made in America, but which may be obtained in this country. These are shown in Figs. 110 and 112.
160
CONCRETE ROADS
FIG. 108. — Victoria Mixer with Bucket Distributor.
Tamping and Finishing the Concrete
In the United States, a self-propelling template and tamper (see Fig. 115) is sometimes used. This is now being introduced into the United Kingdom by the Allied Machinery Co., Ltd. At the front of the machine is a strike-off board which levels up the concrete, leaving the surface about half an inch high, a power-driven tamping-bar then consolidates the concrete, and a power-driven belt finisher at the rear of the machine smooths up the surface to a trowel finish.
The surface of a concrete road may be finished with a wooden float or trowel applied by hand, the workman kneeling or lying on a suitable "bridge."
FIG. 1U9.— Rex Paver.
MECHANICAL DEVICES FOR MAKING ROADS 161
FIG. 110. — Special Road Forms.
FIG. 111. — Use of Lute to place Concrete
FIG. 112. — Special Road Forms.
M
164
CONCRETE ROADS
FIG. 113. — The Milwaukee Paver, showing method of loading.
FIG. 114. — The Milwaukee Paver, showing method of discharging.
MECHANICAL DEVICES FOR MAKING ROADS 165
It is, however, preferable, when a sufficient length of roadway is constructed to justify the expense, to mount the bridge on end wheels, and to provide it with a simple propelling mechanism. A particularly effective arrangement developed by the Walker- Weston Co., Ltd., 7 Wormwood Street, E.C.2, used in construct- ing concrete roads at the Victoria Docks of the Port of London Authority, is so arranged that once the road-bed is graded and the reinforcement laid thereon there is afterwards no necessity for any machines or men to stand on the road formation (see Figs. 116 and 117). It consists of a light timber framework structure completely spanning
FIG. 115. — Showing self-propelling Template and Tamper.
the whole width of the road, and carried on either side on a bogie mounted on rails. One bogie mounted on a track of 4 ft. 8£ in. gauge carries an electrically-driven concrete mixer, and also an electric motor driving a pair of friction winches. The bogie on the other side of the road is mounted on a 24-in. gauge track and carries the other end of the framework. This framework is covered over with tarpaulin, and its interior can easily be lighted or heated so that work can proceed, if necessary, by day and night, and also in frosty weather. To the under side of the ridge of the framework structure is attached a cableway actuated by friction winches, by means of which the concrete skip is conveyed from the concrete mixer to any part of the road under the " tent." Boards laid opposite each other, transversely across the " tent," form a platform or bridge on which stand the two men who work
166
CONCRETE ROADS
the strike board for smoothing the concrete surface. Roads 30 ft. wide are " struck " or screeded in three strips, and when screeding the crown or centre strip, each end of the board rests on two fixed
FPJWfrtG COYE&eD MTH CJNV/iS
3 /DEL ELS: VA 77 o/y .
FIG. 116. — Road-laying machine used for concrete by the Port of London Authority.
angles carried transversely across the base of the " tent " and parallel to the longitudinal axis of the road. These angles are easily adjusted
FIG. 117. — Reinforced concrete road in course of construction, showing the Road -laying Machine in use.
and fixed to the correct height to enable the board automatically to strike off the surface to the correct level. The strips of road on each side are treated in a similar manner, with the exception that
MECHANICAL DEVICES FOR MAKING ROADS 167
the gutter-end of the board rests on a board fixed to pegs in the ground and graded to the levels required for the gutters.
Some engineers prefer to finish the surface by rolling, using a roller made of light sheet steel 8 in. diameter and 6 ft. long and weighing about 70 Ib. The roller has a handle of such a length that the operator can stand at one side of the road and push or draw the roller completely across it, or two ropes may be attached to the shaft of the roller, so that it may be drawn across the road by a man on each side of the latter.
The roller should not cross the road at right angles, but at such an angle that it advances about 2 ft. along the road at each crossing. It is usually necessary to roll the surface three times in this manner.
An alternative method consists in drawing a belt of rubber or rubber-faced canvas at least 2 ft. longer than the width of the road and 8-12 in. wide, to and fro and longitudinally across the surface. The belt should be moved in strokes about 12 in. in length, across the road, the movement along the road longitudinally being very slight. In a second, similar application of the belt, the strokes should be quite short — only about 4 in. — and the movement along the road much greater than before.
A popular method of finishing road surfaces in the United States is a combination of the two processes just described.
REINFORCEMENT NOTES.
The roads at the following places mentioned in this volume were reinforced with the British Reinforced Concrete Engineering Com- pany's Fabric: Abergavenny, Bath, Belfast (3), Buckhurst Hill, Cardiff, Chester (3), Chisledon, Deptford, Dunfermline, Gravesend, Greenhithe, Loch Doon, Longhoughton, Melbourne, Mountnessing, Newbury, Newport-Cardiff, Portsea Island, Purfleet, Southampton, Swindon, Sydney, Taunton, Tilbury, Totnes-Paignton, Tredegar.
The Expanded Metal Company's Rib Steel Reinforcement was used in the following roads : Roberts Lane, Chester ; Marine Drive, Exmouth ; Fish Quay, Padstow ; and on the sea front, Sidmouth.
Triangle Mesh was employed in the B road Portsea Island Gas Works, and Goods Yard, L.B. & S.C. Ry., East Croydon.
The Walker-Weston Patent Pyramidal Interlocked Reinforcement at the Royal Victoria Dock (Port of London Authority).
The other roads were reinforced on non-proprietary systems.
CHAPTER VII CONCRETE KERBING
CONCRETE kerbing and channelling have been used extensively in many of our counties, and the practice adopted by surveyors in Surrey, Brighton and Aylesbury, may serve as a useful guide as to the method for making kerbs of concrete.
Aylesbury. — Mr. W. H. Taylor, Borough Engineer and Surveyor of Aylesbury, gives the following account of concrete kerbing in his district : —
The Aylesbury Corporation have made concrete kerb and chan- nelling for the past eight years. The kerbs are 5 in. by 10 in. by 3 ft. long, and the top face is chequered to give a good foothold. At the commencement the kerbs were cast in wood moulds, but after a time the moulds became warped and iron moulds were obtained.
The channel-blocks are 9 in. by 4 in. by 15 in. long, and the upper face is slightly dished. They are cast in wood moulds face down- wards.
The materials used for making both the kerb and channel- blocks are one of Portland cement to three of Clee Hill granite chippings J in. to dust. In mixing the materials, great care is taken, as it has been found from experience that this is most essential, or the results are not so good.
The aggregate is measured and well mixed with the cement both before and after the water is added. As the moulds are being filled the material is rammed gently by means of a small wood rammer, and if this is done a good surface is obtained.
Many thousand yards have been laid and the first length is still excellent.
168
CONCRETE KERBING
169
FIG. 118.— Concrete kerb and channel in the Borough of Aylesbury
Section.
Fio. 119. — Concrete pavement gutter in the Borough of Aylesbury.
170
CONCRETE ROADS
Pavement Gutters. — During the War it was found impossible to obtain iron pavement gutters and therefore experiments were made with concrete gutters. They are cast in a wood mould with a 3-in. iron pipe running through the mould. If care is taken in the casting and when being fixed they are found equal to iron gutters. Fig. 119 shows a gutter of this type.
Brighton. — In 1878 the Corporation commenced making concrete kerb and " pitchers," and the first street was laid with concrete kerb and pitchers in that year. Since that date many streets have been laid with that material.
The kerbs and pitchers have been made in the Corporation's own stores in iron moulds by hand and without pressure, the kerbs 30 in. by 11 in. by 5 in., and pitchers 18 in. by 6 in. by 4 in. They have been found to be a very useful and cheap substitute in the case of roads having ordinary traffic. They were at first made with beach shingle and cement, 3 parts shingle, 1 part sand, and 2 parts cement, but afterwards, owing to the slippery nature of the shingle, granite was substituted. These, with granite, were made at a cost of Sd. per foot lineal, against Purbeck stone at Is. 3d., and granite at Is. Qd.
Concrete slabs were also made by hand, and the first were laid in 1881 in one of the busiest streets of the town and are still in existence ; York stone laid adjoining has been replaced on two occasions.
FIG. 120.— Moulds for kerbs at Brighton.
CONCRETE KERBING
171
FIG. 121. — Concrete kerb and pitcher, and cement paving laid in 1878,
in Brighton.
FIG. 122. — Concrete kerb laid in 1881 (and cement paving laid later),
in Brighton.
CONCRETE KERBING 173
Concrete has been much used in Brighton. The wall at the south side of Marine Parade was built in lime concrete by a local builder in 1830-1834. This wall, in places, is 50 feet high, has a batter on the face of 1 in 6, is 2 ft. thick at the top, and the back is vertical. This cost about £100,000.
The first cement concrete groyne for sea defence was built in 1865, and at the present time all the wooden groynes have been removed and concrete groynes substituted.
Surrey. — Mr. Alfred Dryland, M.Inst.C.E., late County Surveyor of Surrey, now of Middlesex, has furnished us with the following interesting details and illustrations of the method adopted by him : —
The first kerb put down in Surrey was a reinforced concrete submerged retaining wall or abutment to the carriage-way, and was evolved from considerations of, and investigations into, the apparent weakening of the road crust at the sides by movement or " creep " in the cross-fall direction where the roadside wastes were soft or the ditches unpiped, and was primarily intended to remedy such defects as arose from this cause. The kerb was laid in situ and was 9 in. deep by 4 in. wide and reinforced with two steel rods £ in. diameter in the positions shewn in Fig. 123.
The kerb was put down to levels to coincide with the finished top or carpet coat of the carriage way when laid. A trench 8 in. wide was excavated to required depths and 9 in. by 2 in. deal shuttering held in place with iron road-pins was fixed in proper position four inches apart. Concrete composed of four parts clean crushed ballast to pass half -inch mesh sieve, two parts clean sharp sand and one part British Standard Specification Portland cement (all measures by bulk) was deposited between the shutters and tamped and trowelled off on top and the reinforcing rods inserted in their proper positions as the work proceeded. The shutters were painted with soft soap and were allowed to remain for three days, when they were removed without difficulty and with- out detriment to the concrete kerb, which was immediately cov- ered over with a small mound of earth and left to set for at least 28 days. Where the ground was sufficiently deep and compact and could be cut in a straight regular face, no shuttering was used on the back face. At bends or curves in the road 9 in. by 1 in. shutters were used to obtain an easy sweep. The kerb was con- tinuous and being practically submerged, and therefore not liable to great changes in temperature, no expansion joints were con-
174
CONCRETE ROADS
FIG. 123. — Method of constructing submerged concrete kerb in Surrey.
sidered necessary, this conclusion being substantiated by the total absence of cracks, damage, or movement so far as obser- vations can detect. This retaining kerb performs its functions successfully and is one to be recommended in rural areas where building developments are slow. For use upon main roads and others in districts where, in anticipation of housing schemes, foot- paths are essential in the completed road, an elaboration of this kerb was adopted, and is designed not only to retain the road crust but also to keep traffic within the boundaries of the carriage- way and form an edge to the footpath. It is shown in Fig. 12 4. The trench in this case is dug 9 in. wide and generally to a depth of fourteen inches below the intended path level, and a layer of concrete 9 in. wide and 5 in. thick composed of five parts ballast to pass a 1-in. mesh sieve, two parts broken clinker and ashes, one part clean sharp sand, and one part Portland cement, is laid iii the trench. The shutters, which are again 9 in. by 2 in., planed on one face, and coated with oil or soft soap, are secured in position on this bed of concrete to show 5 in. between faces. The reinforcement is fixed in the line of neutral axis on a vertical plane in order to resist as far as possible reversals of normal stress which undoubtedly occur, and although not in conformity with theory, it was contemplated that in this position it would oppose the necessary tensile resistance to any bending and unbalanced stresses brought to bear upon it in any direction and avoid the cost of two lines of reinforcement. It consists of a strip of " Exmet " expanded metal f-in. diamond mesh 9 in. wide, cut in lengths of about 16 ft. for convenient handling. To ensure continuity of the reinforcement an overlap of about 2 in. is arranged at each join, but to provide for expan- sion of the concrete, joints are made at every 15 to 18 ft. by intro- ducing a layer of tarred felt into the cross section of the kerb. This is slit and passed over the reinforcement. Five to one con- crete is then poured in to such a height as will bring the kerb
CONCRETE KERBIXG
175
to road level, and above the road level a three to one concrete con- sisting of one part £ in. crushed ballast, one part |-in. to dust granite chippings (to give "case hardening"), one sand and one Portland cement, is added and tamped against the shutters and smoothed off on top. To eliminate the sharp angular edge a chamfer is trowelled on the kerb about one inch wide, or to effect the same purpose a hard wood fillet can be nailed to the front shutter. On gradients where traffic in many instances uses the kerb to form a "drag" upon the vehicle, a protecting steel strip is embodied in the kerb immediately below the chamfer. It is
FIG. 124. — Method of constructing concrete kerbs in Surrey.
\\ in. by & in., and is secured every 2 ft. by bent wire nails as shown in Fig. 124.
The nails are countersunk into the steel and are finished flush, so that no " bite " can be got of them by wheels, which would cause damage difficult to repair.
It is essential when removing the shutters to cover over the kerb for at least a month to ensure thorough setting, as it is subjected to a considerable amount of grinding and buffeting from the wheels of vehicles. Many miles of this kerb have been laid and give every appearance of proving entirely successful, both from a constructional and financial point of view, the cost at present prices being little more than one-third the cost of granite. For this class of work a gang of eight men is required, and, when experi- enced, 50 to 60 yds. per day can be averaged. The shutters can
176 CONCRETE ROADS
be used many times over, and by hooping the ends before use the life of the boards is greatly increased.
Integral Kerb. — Where concrete footpaths are laid, a method more recently adopted is that of forming the kerb in situ as part of the footpath itself. This is done by erecting a planed 3-in. plank along the kerb line in a trench, the kerb and paving being laid together with a joint every six feet. In this method the greatest care is required in the alignment of the planks. They must be very rigidly supported with stakes, or bulging will occur. The cost is rather less than when the kerbing is moulded separately.
There are many other examples of concrete kerbing which could be mentioned, as this class of work has been carried on for many years. In Gravesend and Northfleet, for instance, concrete kerbs were put down more than thirty years ago.
CHAPTER VIII
SUGGESTIONS FOR A FORM OF SPECIFICATION FOR CONCRETE ROADS
IN submitting the following suggestions, it must be clearly under- stood that they are put forward more in the light of a useful guide when drawing up a specification for making concrete roads, than laying down any hard and fast formula.
There will always be found, from time to time, certain conditions in road construction requiring special treatment, and undoubtedly these are matters which will naturally engage the close attention of the road engineer, surveyor or contractor in charge of the work. It may be stated, however, that the suggestions set out have been compiled after much study and observation of concrete road work in this country, and in addition, valuable aid has been rendered by those who have had considerable experience in the most modern and successful methods of concrete road-making in America. These notes are, therefore, presented in the full belief that they will be found reliable and instructive in framing the definite principles of a specification.
Materials
1. Cement. — The cement shall be supplied by a British manufacturer of repute, and shall comply with the requirements of the British Standard Specification for cement in force for the time being. It shall be of the " slow-setting " quality as defined in that specification. Conditions as to testing, delivery and storage shall be agreed between the vendor and purchaser.
2. Aggregates. — Great care shall be taken in the selection of the aggregates. The actual materials to be used must depend upon local circumstances, subject to the following limitations : —
No natural deposits of sand and gravel shall be used without washing, screening, and grading to comply with the conditions hereinafter laid down.
Jf crushed stone is used it shall be screened, graded, and, if
177 N
178 CONCRETE ROADS
necessary, washed, to comply with the conditions hereinafter laid down.
No aggregate shall be used which is not hard and tough, or which is laminated, and upon crushing breaks down into flat or elongated particles. Soft or porous materials, such as broken brick, breeze, etc., shall be prohibited.
All aggregates used shall be clean and free from clay, dust, vegetable and other foreign matter. Care shall be taken that the aggregate is not contaminated with mud, etc., after delivery to the site of the work.
Coarse Material. — For one-course roads no aggregate shall be used which will not pass through a screen having square openings of 1 in. ; but for two-course roads the bottom course may contain aggregate the largest stones in which will pass through a If -in. square opening. None of the coarse material shall pass through a J-in. square opening. The grading from the maximum to the minimum sizes shall be regular, and no material shall be used which contains a large proportion of stones of approximately one size.
Sand or fine material shall all pass through a J-in. square open- ing, but not more than 10 per cent, by weight shall pass a sieve having 50 meshes per lineal inch. The grading from the maximum to the minimum sizes shall be regular, and no material shall be used which contains a large proportion of particles of approxim- ately one size.
Representative samples of the approved coarse material and sand shall be retained by the surveyor in charge of the work, and all deliveries shall be required to conform strictly to such samples.
3. Concrete. — The average compression resistance of not less than three test pieces of the concrete shall not be less than will comply with the following formulae : — •
When 4 weeks old :— C 1 = 2,800—200 V, and When 13 weeks old :— C 3 = 3,600—200 V, where
C 1 and C 3 = compression resistance in Ibs. per sq. in.
V= Volume of sand and coarse material per volume
of cement.
For determining the compression resistance, tests shall be made on cubes or cylinders of not less than 6 in. each way. The prepara- tion, setting and maturing of the test pieces shall, as far as possible, conform to the conditions that will pbtain in the actual execution of the work, provided that care must be taken to see that the conditions for all test pieces are as uniform as practicable, and that none of them is exposed to frost during setting and maturing. The compression resistance of any test piece which gives such a
SUGGESTIONS FOR FORM OF SPECIFICATION 179
low result as to indicate a faulty specimen shall be eliminated in arriving at the average of the results for any test.
4. Water. — The water" shall be fresh and clean, and shall be taken from a public drinking water supply or from other source of known purity.
5. Reinforcement. — All metal for reinforcement shall be free from oil, paint, excessive rust, or coatings of any character which will tend to destroy the bond with the concrete. The metal shall develop an ultimate tensile strength of not less than 60,000 Ibs. per sq. in., and withstand bending when cold 180 degrees around one diameter and straighten without fracture.
6. Joint Filler. — Joint filler must be an elastic waterproof material, which will not lose these properties under extremes of weather conditions.
Preparation of the Existing Surface
7. Foundation. — The preparation of the foundation will necessarily vary with local conditions, and must be determined by the sur- veyor in charge of the work. Any necessary embankments or fills shall be executed to the satisfaction of the surveyor, and shall be thoroughly consolidated, so that there is no possibility of settle- ment at any point. Any soft or weak places must be excavated and filled up with hard stone or other suitable material, so as to obtain solidity equal to the remainder of the surface. The sur- face shall be finally rolled to the required contour with a roller of not less than 10 tons in weight. It should be noted that the use of concrete for the road cannot be assumed to do away with the necessity for a good and even foundation over the whole surface.
The surface thus prepared shall be regular and may be flat, or with a slight cross fall as may be specified by the surveyor.
When the road is not supported by kerbing on either side, a channel may be dug, longitudinally, immediately inside the edge of the prepared base, so that the concrete when placed has a cross section at this point as shown in Fig. 125.
Immediately before the concrete is placed, all foreign matter shall be removed from the prepared surface, which shall then be thoroughly watered.
8. Drainage. — -Where local conditions require, a suitable drainage system shall be provided to the satisfaction of the surveyor.
180 CONCRETE ROADS
Concrete
9. Proportions. — The coarse material and sand shall be used by volume in such proportions, one to the other, as are found by trial with several mixtures of the same total quantity measured separately, but of varying proportions, to give the least volume of concrete when mixed with the prescribed quantity of cement and tamped into a mould of known capacity.
For one-course roads not more than 5 parts of coarse and fine aggregate, mixed as provided, to one of cement shall be used. Generally speaking, where severe traffic conditions are likely to be met, the concrete for a one-course road should be in the proportions of 1 part of cement to 1 ^ parts of fine aggregate and 3 parts of coarse aggregate. For two-course roads not more than 8 parts of coarse and fine aggregate, mixed as provided, to one of cement shall be used for the lower course, and not more than 3 parts of fine aggregate to one of cement for the upper or surface course.
10. Measuring the Materials. — The method of measuring the materials for the concrete, including water, shall be one which will ensure uniform proportions at all times. The cement shall be taken by weight on the basis that 90 Ib. is equivalent to a volume of one cu. ft.
11. Mixing. — The concrete shall be mixed in a batch concrete mixer of an approved type. The mixing shall continue until the in- gredients are homogeneous and plastic throughout. The drum shall be completely emptied after mixing each batch.
12. Consistency. — The quantity of water to be added to the concrete shall be such as to secure a plastic mixture which can be easily worked, and so that only light tamping shall be necessary to con- solidate when placed in position. Care shall be taken to pre- vent an excessive amount of water being used, and the concrete shall not be so sloppy as to cause a separation of the coarse aggre- gate from the mortar during handling and laying.
Any concrete which has partially set before being placed in position shall not be used. To avoid waste from this cause, all concrete which is mixed ready for placing in position imme- diately before the dinner hour or other stoppage of the work shall be placed and finished before stopping. Under all circumstances as little time as possible shall elapse between the mixing of the concrete and placing and finishing.
SUGGESTIONS FOR FORM OF SPECIFICATION 181
Placing the Concrete
13. Weather Conditions. — So far as is practical, all work should be clone during the summer months, but in the event of concrete roads having to be laid when the thermometer is below 39° F., care shall be taken that the sand and stone shall be heated before being introduced into the mixing drum, or that an intense heat shall be brought to bear on the concrete during the mixing process. During such weather conditions, after material is put in place on the road, care should be taken that it is thoroughly protected, preferably by tenting with canvas under which steam pipes or braziers shall be introduced to ensure that the temperature of the concrete will remain above freezing point until the concrete has had time thoroughly to set.
The concrete shall be deposited over the whole width of the road at one and the same time, except in cases where it is impossible to divert the traffic for the time being. The sides of the road, where there is no kerb, and the end of each day's work, shall be supported by a wooden or metal form sufficiently strong and properly supported to resist straining out of shape under the pressure of the concrete. All mortar and dirt shall be removed from forms which have been previously used, and the forms shall be greased or oiled before any concrete is deposited against them. The side forms shall remain in place until the concrete is set sufficiently hard to permit of the removal of the forms without damage to the edges. In removing the form at the end of the previous day's work, in order to resume operations the next day, very special care will have to be taken to see that the concrete is not damaged, and, furthermore, in beginning the deposition of concrete special care must be taken with the tamping of the concrete to see that the previous day's work is not disturbed or damaged in any way. This will, inevitably, be one of the most critical points in the road and will merit the very closest attention and supervision. If desired, joints filled with material complying with paragraph 6 may be provided between each day's work, but shall not exceed J in. in thickness. The value of these joints, however, is not proved, and they undoubtedly introduce weak points into the road. Longitudinal joints similarly filled may also be provided alongside the kerb or channelling (if any) if desired.
14. Thickness. — The total thickness of concrete for both one and two-course roads shall be specified, and it will be found that, under average conditions, a total thickness of about 6 in. will probably be sufficient. The surface course of two-course roads shall be approximately 2 in. thick.
182 CONCRETE ROADS
When a two-course road is being laid the upper course or wear- ing surface shall be spread on the lower course immediately after the latter is deposited and before it has begun to set.
15. Consolidation. — Immediately after being placed in position in a roadway, the concrete shall be struck off to approximate grade and camber and shall then be thoroughly consolidated to eliminate all voids and all surface moisture. This consolidation is to be effected by tamping or punning the surface of the concrete, either mechanically or by hand, or it may be done by rolling. In no event shall any tamping device be used which necessitates a penetration below the concrete surface.
16. Surface. — Failing the use of a mechanical tamper, the wear- ing surface shall be struck off to the finished contour by means of a double template, of which a suitable type is shown in Fig. 126. This template shall be drawn over the concrete with a com- bined longitudinal and transverse motion, so as to produce a surface free from depressions or inequalities of any kind, and this surface shall not afterwards be disturbed by floating off or in any other way. The finished surface shall have a cross fall only sufficient, in the judgment of the engineer or surveyor, to ensure that the surface water will pass off the roadway quickly, and shall not vary more than £ in. from true shape. It will be found that, at the most, a cross fall of 1 in 60 will be sufficient.
No cessation of work of more than an hour's duration shall be permitted, except at the end of a completed bay.
In cases where it is impossible to divert the traffic and the con- crete has to be laid on one-half of the road at a time, the edge of the concrete in the centre of the road shall be left with a rough verti- cal edge, and immediately before filling in the concrete for the second half this edge shall be thoroughly swept, watered, and painted with a thin coat of neat cement and water in equal pro- portions. The concrete shall then be applied immediately.
17. Reinforcement. — The concrete may be reinforced with steel reinforcement of a type approved by the surveyor. When, in the opinion of the surveyor, reinforcing is necessary, such rein- forcing should be equivalent to 0-05 square inch per foot width of the concrete. In cases where one-half of the roadway is laid at one time, the reinforcement should be carried beyond the centre edge of the concrete first laid so as to provide a positive connection between the two halves.
i
s-«
184 CONCRETE ROADS
Curing and Protection
18. Watering Surface. — The surface of the concrete shall be sprayed with water as soon as it has sufficiently hardened to withstand pitting, and shall be kept wet until covered as hereinafter provided.
The surface of the concrete shall be covered within 24 hours with clay, earth or other easily obtained material, which shall be kept thoroughly wetted for a period of at least 10 days.
When sunshine, a drying wind, or other conditions make it desirable, in the opinion of the surveyor, the freshly laid concrete shall be protected by canvas laid on a wooden framing or other covering until set sufficiently to be watered and protected as prescribed.
19. Opening to Traffic. — Under the most favourable weather condi- tions the concrete road shall not be opened to traffic until at least twenty-one days after it is laid, and when the weather is cool or wet this period shall be increased for such additional time as may be necessary in the opinion of the surveyor.
Where the road is constructed in two halves owing to the impossibility of diverting the traffic, the traffic should not be concentrated on to the first half which has been concreted until at least thirty-five days after completion, or longer where weather conditions make it desirable in the opinion of the surveyor.
CHAPTER IX THE USE OF CONCRETE FOR ROAD ACCESSORIES
Introduction. — In reviewing the constructional methods of the past, nothing, perhaps, will be found to be more striking than the large and ever increasing variety of uses to which concrete, during recent years, has been applied for the production of articles and structures of a permanent nature which were formerly made of timber, brick, iron or steel. The reason for this is undoubtedly to be found in the improved methods of making and handling concrete, which have resulted in a fuller appreciation of its superi- ority for many purposes, over other materials of which it is rapidly taking the place.
Structures or articles made of wood, iron, or steel, soon begin to deteriorate, and unless paint or other preservative is used will depreciate very quickly. Concrete, on the other hand, not only requires no paint or preservative of any description, but actually improves with age, becoming stronger and stronger over a long period of years.
Thus it will be seen that, although the initial cost of concrete may, in some cases, slightly exceed that of other material, this is more than compensated for by its great durability and low cost of maintenance.
If any evidence were wanting as to the efficiency and economy of concrete, it would be found in the extensive way in which the great railway companies and some municipal bodies have adopted this material for a large variety of uses, and for which purpose they have laid out and equipped their own concrete yards. In this connection special mention should be made of the work being done at Taunton by the Great Western Railway Company, who were the pioneers of this type of construction ; at Exeter by the London & South-Western Railway Company ; at York by the North- Eastern Railway Company, and many others which might be quoted. Excellent examples of this class of work may be seen at the Per- manent Exhibition of Concrete Products which has been installed
185
186 CONCRETE ROADS
at 143 Grosvenor Road, London, S.W.I, by the Concrete Utilities Bureau of 35 Great St. Helens, London, E.G. 3.
No book on concrete roads would be complete without some suggestions with regard to numerous accessories to roadways which might well be made of concrete, and the following hints are submitted in the hope and belief that they will be of interest to the reader.
Pavements. — Modern requirements demand that the ideal footpath or pavement shall be smooth without being slippery, even, durable, clean and unaffected by climatic conditions. These requirements are met in a striking manner by concrete, provided that the material itself is of the first quality, and that the job be carried out in an intelligent and workmanlike manner. Little, however, need be said here about concrete footpaths, since these, either in the form of slabs or concrete laid in situ, are rapidly replacing those of other materials, and they have been so long before the public that their strength, durability and general efficiency have been convincingly proved.
Kerbs and Channelling. — This subject, a very important one, has been fully dealt with in Chapter VII.
Fig. 127, showing a tree-guard for pavements, illustrates another use for concrete as a substitute for iron. As will be seen from the photograph the tree-guard is in the form of lattice work, each bar of which is reinforced by a single steel rod.
Reference has already been made in Chapter VII to the pavement gutters produced in concrete by the Aylesbury Borough Council.
Culverts. — In connection with rural roads concrete culverts are coming into general favour. If constructed in situ, they should be built during the dry season, if possible, or the water may be diverted during their construction by building a dam above the culvert and conveying the water away from the work by means of temporary troughs or pipes.
A method often adopted is that of employing pre-cast culvert blocks or half-pipes, which, when cemented together, form the culvert. No reinforcement is used in structures of this nature. Fig. 129 is an illustration of this type of culvert.
Sewer Pipes and Water Mains. — Considerable economies can be effected and increased efficiency secured by the use of concrete sewer pipes and water mains. These are being adopted here and in various parts of the world with great success.
Concrete pipes are usually made either in vertical iron moulds, or are cast on the centrifugal method in horizontal moulds.
USE OF CONCRETE FOR ROAD ACCESSORIES 187
FIG. 127. — Tree Guard.
FIG. 128. — Manhole.
FIG. 129. — Culvert.
190
CONCRETE ROADS
i
JB&
I
FIG. 131. — Station Name-plate.
FIG. 130.— Tele- graph Post.
FIG. 132. Lamp Post,
FIG. 133.— Concrete Pipes.
USE OF CONCRETE FOR ROAD ACCESSORIES 191
The advantages of concrete over iron for pipes are the low initial cost, and the fact that concrete does not corrode. Modern scien- tific research suggests that the corrosion of iron pipes is largely due to electrolysis ; in a properly made concrete pipe in which the reinforcement is completely embedded this danger is eliminated, with the result that the life of such pipes is indefinite.
In order to avoid disturbance of the concrete roadway, in all cases where it is possible to do so, sewer pipes, gas and water mains and electric conduits should be laid under the pavement where they would be more accessible, and a minimum of inter- ference with the traffic would be caused when repairs were necessary.
Manholes and Inspection Chambers. — Fig. 128 shows a concrete man- hole. This, of course, could be moulded in situ, but a more con- venient form of construction is that adopted in the case of the manhole shown in the illustration ; that is to say, a series of pre-cast concrete rings which, when the excavation has been made, are lowered into position, one on top of the other until the surface is reached, the joints being grouted if necessary according to circum- stances. It will be seen at once what a saving of time is effected by this method over the old practice of bricking up the manhole. Inspection chambers may be constructed in the same way with pre-cast concrete blocks.
Fence Posts and Gate Posts. — The value and importance of good fencing are appreciated by all who are responsible for the enclosure of land and who know from experience what constant attention, time and expense are required in order that the fences may be kept in proper condition.
The material most commonly used for fencing is wood, but this is not only high in price and increasingly difficult to obtain, but, used for this purpose, it has a short life, is expensive to maintain, and is not fireproof. For these reasons, wood is being rapidly and extensively replaced by concrete since this material meets all the demands made upon it. The reinforced concrete post is reason- able in first cost, it may be made on the spot if so desired, local unskilled labour can be used in its construction, it may be moulded to any design, is hard and strong, does not decay, requires no painting, is fire-resisting, and with ordinary usage is practically everlasting ; indeed, after a period of years when a wooden post would have to be renewed, the concrete post is stronger than when it was first put into the ground.
The utility and the economy of concrete for this purpose are demonstrated by the fact that this form of fencing is being adopted to an increasing degree by municipal bodies ; and those who travel
192 CONCRETE ROADS
by rail must have been struck by the great and growing mileage of concrete fence posts which are rapidly replacing wooden ones along the lines of practically all the companies. These facts point to the suitability of concrete fencing for rural highways.
Telegraph and Telephone Poles, Electric Light Standards and Trans- mission Poles. — Concrete, owing to its great strength and dura- bility, forms an efficient substitute for iron or wood in the making of telegraph and telephone poles, electric light standards and trans- mission poles. In early days when poles of this description were made solid their great weight was found to be a disadvantage, but with improved methods of moulding and reinforcing these articles are made much lighter and their adoption is being rapidly extended. In addition to their low initial cost, the advantage of course lies in the fact that concrete does not decay as wood does, nor does it require painting, which is necessary in the case of the iron pole in order to prevent corrosion.
Lamp Posts. — Concrete being in its wet state a plastic material, is one which can be moulded to any shape. It is not surprising, therefore, that artistic lamp posts may be fashioned of concrete, and if properly made and suitably reinforced are an effective substitute for the iron post. This is a direction in which municipal authorities might, with advantage, adopt a method of construc- tion which is at once efficient, economical and pleasing to the eye. Examples of concrete lamp posts may be seen at the Permanent Exhibition of Concrete Products to which reference has already been made.
An example of a concrete telegraph post and of a lamp post made by the L. & S.-W. Railway Company, are shown in Figs. 130 and 132.
Street Name Plates. — Street name plates can be made with advantage in concrete. It is not generally known that concrete can be made in any colour. In the case of the railway station name boards which are now being made of concrete, the lettering is of permanent black concrete on a light-coloured concrete background, so that no paint is required, and all that is necessary to keep the name plate clean and legible is an occasional wash. If this type of sign has been found to be satisfactory in the case of railway station name boards, why should it not be adopted for street name plates, which are easily made and if moulded on glass are perfectly smooth and polished ?
Road Signs. — Since concrete has been found suitable for railway gtation name plates, it can also be readily adapted for road signs,
USE OF CONCRETE FOR ROAD ACCESSORIES 193
whether in the form of direction posts or of the various cautions and danger signals adopted by the Automobile Association and Motor Union. These, as we have suggested, could be made entirely of concrete. Black letters on an approximately white ground would be sufficiently clear to the passing motorist, and the economy effected by the use of a material which needs no expense for upkeep should appeal to the authorities who have control of these road signs.
INDEX
Aggregates, 177
Coarse Material, 178
Amelia Street, Southwark, 1
American Roads, 115
Anzac Avenue, Auckland, N.Z.,
102 Appliances used for Preparing
Road-Bed, 124 Avenue Road, Southwark, 2
Backfillers, 132
Baker, Sons & Perkins, Willes-
den Junction, 75 Beach Road, Auckland, N.Z., 102 Blackwood Crescent, Edinburgh,
64 Brecon and Abergavenny Main
Road, 55 Brockham Street, Southwark, 2
Canmore Street, Dunfermline, CO Cement, 177 Chisledon, 85 Concrete, 178, 180, 181
Consistency, 180
Measuring the Materials, 180
Mixing, 180
Proportions, 180 Consistency of Concrete, 180 Consolidation, 182 Content Street, Southwark, 2 Conveyors, 137 Cranes and Grabs, 126 Crushers, 138 Culverts, 186 Curing and Protection, 184
Opening to Traffic, 184
Watering Surface, 181
Deverill Street, Southwark, 2 Disintegrators or Cage Mills, 143
Dock Road, Tilbury, 34 Drag-Line Excavators, 131 Drainage, 179
Durham Street, Auckland, N.Z., 101
Electric Light Standards, 192 Elevators, 147, 153 • Empire Paper Mills, Green-
hithe, 76 Epping New Road, Buckhurst
HiU, 32 Exchange Lane, Auckland, N.Z.,
102
Factory Road, Southampton,
78
Fence Posts and Gate Posts, 191 Finishing Appliances, 160 Foregate and Eastgate Streets,
Chester, 21 Foundation, 179
Gate Posts, 191 Glengormly, Belfast. 67 Grading Machines, 137
Hand and Horse-operated
Rollers, 137 Heiron Street, Southwark, 2
Inspection Chambers, 191 Integral Kerb, 176
Jaw Crushers, 143 Joint-Filler, 179
Keeping Aggregates Clean, 148 Kerbing :
Aylesbury, 168
Brighton, 170
Surrey, 173 Kerbs and Channelling, 186
195
196
INDEX
King's Wharf Road, Auckland, N.Z., 102
Ladder Excavators, 132
Lamp Posts, 192
Lawson Street, Southwark, 2
Laying the Concrete, 159
Little Queen Street, Auckland, N.Z., 99
Loch Doon Road, 85
London, Brighton and South Coast Ry. Goods Yard, East Croydon, 86
London-Dover Road, Graves- end, 44
Longhoughton Road, Northum- berland, 56
Lorimore Street, Southwark, 2
Lower Bristol Road, Bath, 59
Main North Road, Northum- berland, 56
Manholes and Inspection Cham- bers, 191
Marine Drive, Exmouth, 22
Market Roads, Auckland, N.Z., 102
Measurement of Water, 153
Measuring the Materials, 180
Mixers, 153
Mixing, 180
Motor Rollers, 138
Mountnessing Road, Essex, 31
New King Street, Deptford, 6 Newport-Cardiff Road, 44 New South Head Road, Sydney,
108 Northbrook Street, Newbury, 10
Opening to Traffic, 184
Padstow Station, 22
Park Road, Auckland, N.Z., 101
Pavements, 186
Penton Place, Southwark, 1
Placing the Concrete, 181
Consolidation, 182
Reinforcement, 182
Surface, 182
Placing the Concrete —
Thickness, 181
Weather Conditions, 181 Port of London Authority, The,
69
Portsea Island Gas Works, 78 Preparation of the Existing Sur- face, 179
Drainage, 179
Foundation, 179 Preparing Concrete, 138 Proportions, 180
Quay Street Extension, Auck- land, N.Z., 102 Queen's Row, Southwark, 2
Ralph Street, Southwark, 2
Reinforcement. 179, 182 .
Reinforcement Notes, 167
Road Accessories, 185
Road Signs, 192
Roberts Lane, Saltney, Chester,
17 Rollers and Tampers, 137
St. Kilda Road, Melbourne, 107
Screens, 144
Sewer Pipes and Water Mains,
186
Southampton Docks, 41 South Street, Southwark, 2 Specification, Suggestions for, 177 Standard Street, Southwark, 1 Steam Rollers, 137 Steam-Shovels, 124 Steedman Street, Southwark, 1 Street Name Plates, 192 Surface of Concrete, 182 Symonds Street, Auckland, N.Z.,
102
Tamping and Finishing the
Concrete, 160 Telegraph Poles, 192 Telephone Poles, 192 Theobald Street, Southwark, 2 Thickness of Concrete, 181 Thurlow Street, Southwark, 2 Toronto-Hamilton Highway, 108
INDEX
197
Totnes-Paignton Road, 29 Trafalgar Street, Southwark, 2 Traffic, Opening to, 184 Transmission Poles, 192 Transporting the Materials, 147 Tree Guards, 186 Trench Excavators, 131
Wa tiding Street, Southwark, 2
Wn irons, 137
Warner Street, Southwark, 1
144 Water, 179 Water Mains, 186 Watering Surface, 184 Weather Conditions, 181 Westmoreland Road, Southwark,
2 Wheel Type Trench Excavators,
131
Whitefriars, Chester, 18 Wooler Street, Southwark, 2
ENGINEERING NOTES. DECEMBER 15th 1920. In an interesting article on
REINFORCED CONCRETE ROADS
The subject is referred to in the following manner : —
" The adoption of reinforced concrete in the con- struction of roads, although never taken up with the same enterprise in this Country as in the United States and Canada, is becoming more general, and amongst road engineers the opinion is gaining ground that if efficiently constructed of proper materials a reinforced concrete road is capable of proving very durable even under the heaviest of traffic and can also be made to present a surface upon which the necessary tractive effort is reduced to a minimum, which is an important matter relative to modern methods of motor trans- port. . . ."
ADVERTISEMENTS
Patent Double- Layer Interlocked Reinforcement
for Concrete Roads
and Foundations.
This System is used by THE PCRT CF LONDON AUTHORITY, THE COUNTY BOROUGH OF EAST HAM, MESSRS. HARLAND & WOLFF, LTD., MESSRS. WATNEY, COMBE, REID & Co., LTD., THE LONDON & NORTH WESTERN RAILWAY Co. ETC., ETC. :: ::
Apply for Designs and Estimates to the Manufacturers and Patentees:
THE WALKER-WESTON COMPANY, Ltd.,
Empire House, 7 Wormwood Street, London, E.C.2.
ii •
ADVERTISEMENTS
:GIEMT
YjT/E supply the complete
• plant for the con- struction of roads from grading to the finished sur- face.
For twenty-five years our engineers have been con- stantly improving labour aiding machinery for mak- ing concrete roads, giving special attention to those details which produce a better concrete.
For grading or regrading roads, the THEW STEAM NAVVY, also the AUS- TIN and WESTERN ROAD GRADER, DRAG and WHEEL SCRAPERS .
For handling the material, AUSTIN GYRATORY or JAW CRUSHERS, SCREENS, ELEVATORS and BINS. LAKEWOOD HAUL- AGE OUTFITS for conveying materials to the LAKEWOOD PAVING MIXERS and FINISHING MACHINES— these are all in successful use throughout the country. These machines offer ideal methods for mixing, placing and finishing concrete ; the concrete being thus thoroughly mixed, consolidated and given a finished surface with assured precision.
We maintain a staff of experienced constructional engineers who can give you unbiased advice as to the methods best adapted to each job. At your request they will call upon you and arrange for a cinema demonstration, showing all these machines under working conditions. Special catalogues describing each machine will be forwarded to you upon request. SEND FOR YOUR COPY NOW.
STOCKS OF ALL MACHINES CARRIED IN LONDON FOR IMMEDIATE DELIVERY.
ALLIED MACHINERY CO., Ltd.
132 QUEEN VICTORIA ST., LONDON, E.G. 4
Telephone : Telegrams :
City 4253 (three lines). "Alydmachin, Cent. London."
ADVERTISEMENTS
Construction Machinery.
We can supply the following lines of up-to-date Con- struction Equipment, many of which are particularly adaptable to Road Construction.
1. "ERIE" Revolving Steam Excavating Shovel fitted with special mechanical grading device, and
. convertible to Locomotive Crane, Drag Line, Grab, etc.
2. " INSLEY " Quickshift Counterweight Chute Con- crete Placing Plant, Buckets, Towers, Hoists, Chutes, etc.
3. " INSLEY " Mast Hoist Bucket Plant for placing concrete on comparatively small jobs.
4. "BLAW" Steel Forms for every type of concrete work, including BLAW special Road Forms.
5. " BLAW " Grab and Dredge Buckets for handling all kinds of material.
6. "REX" Concrete Paving Mixers, all sizes, also " REX " Building Mixers.
7. " P. & H." Power Traction Tamping Machine.
8. " P. & H." Power Traction Backfiller.
9 . ' *P. & H.' ' Wheel and Ladder Type Trench Excava- ting machines, all sizes.
10. " J.D.ADAMS & CO." Adjustable Leaning Wheel Road Grading Machines.
11. " NOVO " Petrol and Paraffin Engines, 1£ H.P. to 15 H.P. units, Pumping, Hoisting, Compressor, Saw Bench outfits, etc.
Catalogues and full details furnished on request.
GASTON LIMITED,
Construction Machinery Department,
20 Bishopsgate, LONDON, E.G. 2.
Telephone : London Wall 3040 Telegrams: "Gastonorge, Led. London."
IV
AD VERTISEMENTS
CUT YOUR COSTS AT THE START
THE "WINGET WAGON- LOADER
PAYS FOR ITSELF
Height :
1 1 ft. 6 ins.
Width :
3 ft. 6 ins.
Length : 11 ft.
T I ERE'S a handy self-contained wagon loader which will fill a three •*• ^ ton lorry in twelve minutes, and can soon be made to pay for itself. A small non-collapsible type of Elevator, specially designed for filling trucks and wagons with sand, gravel, crushed stone and similar materials, it is light as well as strong, and easily moved about. The total weight is 18 cwt. It is driven by a 2\ h.p. petrol or benzol engine; or, if desired, by electric motor.
WINGET LIMITED
Head and Registered Office:
WINGET HOUSE, 24u Grosvenor Gardens, Westminster, S.W.I.
Foundry and Engineering Works :
THE CAPE, Warwick.
_.. ...TRADE
ADVERTISEMENTS
!|l!llll!!!lllll!l!llllllllll!lllllll!llllllll
™E teAL IN
LAST ;QBOVB CONCRETE
WORD ipSbS^p' MIXERS
WINGET'S
3 CUBIC FEET MIXER
FOR
CONCRETE ROADS
HPHE powerful arms of the " Winget " 3 cubic ft. Mixer — specially •*• adapted to road work and all wet concrete mixing — economise the use of cement and thoroughly mix every particle of aggregate. " In a day's work," writes one well-known Contractor, " We are able to place more concrete with this small mixer than we are with the half cu. yd. steam-driven .... Mixer."
JV/IOREOVER, the "Winget" Mixer can be readily moved from 1V1 point to point, thus obviating, or reducing to a minimum, the barrow run generally necessary when a mixer is used in a fixed position.
IT can be driven by benzol or petrol engine, electric motor 1 or belt.
WINGET LIMITED
Head and Registered Office :
WINGET HOUSE, 24u Grosvenor Gardens, Westminster, S.W.I.
Foundry and Engineering Works:
THE CAPE, Warwick.
.... .TRADE ,^%
VI
A D VERTISEMENTS
TIDNAMS, LTD.,
a WISBECH.
Concrete Specialists,
Manufacturers of Tidnams* Patent
Reinforced Concrete Fencing and Gate Posts
as supplied to the Admiralty, War Office, Road Board, the principal Railway Companies, and most of the County, Town and District Councils.
Fencing on the Market.
The
Cheapest and Best
ALSO MAKERS OF
Reinforced Concrete Posts for Building purposes. Storey Posts and Main Posts of Farm Buildings to receive Concrete Walling.
Concrete Telegraph Poles, Railway Signal Posts, Sleepers and Seat Blocks, Lamp Standards and Guide Posts.
Reinforced Concrete Window and Door Heads, Steps, Sills and Coping.
Cattle Pens, Mangers, Cattle Troughs. Complete Pigsties. Beams and Girders for Bridges, etc.
CATALOGUES ON APPLICATION.
Sole Proprietors of GRIMSHAW'S PATENT STRAINING RATCHETS FOR WIRE FENCING. Works: WISBECH and ARLESEY (Beds). Head Office: WISBECH.
Telegrams: "Tidnams, Wisbech." Telephone: 187 Nat., Wisbech.
ADVERTISEMENTS
vn
EXPANDED METAL
FOR
Concrete Roads and Foundations
UXBRIDGE ROAD, ACTON, MIDDLESEX. EXPANDED STEEL-CONCRETE FOUNDATION TO ROADWAY.
Middlesex County Engineer, MR. A. DRYLAND, M.Inst.C.E.
LITERATURE, PRICES AND SAMPLES ON APPLICATION.
The EXPANDED METAL Co., Ltd.
PATENTEES and MANUFACTURERS OF EXPANDED METAL
YORK MANSION, PETTY FRANCE, WESTMINSTER, S.W.I.
Works :-WEST HARTLEPOOL.
Vlll
ADVERTISEMENTS
ECONOMY
In the construction of roads. Re- inforced concrete is undoubtedly the most economical material obtain- able either for the wearing surface or the foundations, and Triangle Mesh is the cheapest and most efficient reinforcement.
ONE OF TWO REINFORCED CONCRETE ROADS AT CROYDON GOODS YARD, L.fi. & S.C. RAILWAY.
Full particulars, prices and specifica- tion for the construction of roads and foundations free on application —
INDENTED BAR
AND
CONCRETE ENGINEERING Co., Ltd.
QUEEN ANNE'S CHAMBERS, WESTMINSTEfi, S.W.I
Telephone : Victoria 1642.
Telegrams: "Patinbar, London."
ADVERTISEMENTS
SELF - SENTERING EXPANDED METAL
SELF-SENTERING DECKING OVER CULVERTS- NOTE SIMPLICITY OF. TEMPORARY STRUTS.
FOR ROADS,
BRIDGE DECKING, CULVERTS,
SEWERS,
FOOT PATHS.
XN^V/"SX^/WXX
WRITE FOR PARTICULARS TO
SELF - SENTERING EXPANDED METAL WORKS, LTD.,
24 Cannon Street House, Cannon Street, E.C.4.
ADVERTISEMENTS
Road Reinforcement
THE whole durability of a road lies in its foundation, the function of which is to spread the wheel-load over an area that will preclude all possibility of a depression of the ground as the load passes over. Con- crete roads reinforced with Johnson's Steel Wire Lattice have been proved to provide the best highways for all modern traffic conditions. They are the ideal roads for heavy, continuous traffic ; providing a foundation of a lasting resiliency to ensure hard, even wear. They are economical in cost, upkeep, and material, requiring only 6 to 8 inches of concrete against 12 to 14 inches of massed concrete for ordinary roads.
Reinforced Concrete Road Foundations are more economical and more satisfactory than plain concrete. Johnson's Steel Wire Lattice Road Reinforcement effects considerable economies in first costs for labour and materials. Johnson's Steel Wire Lattice is delivered in the form of a complete fabric, ready for laying, in handy rolls of varying lengths and meshes.
Johnson's Reinforced Concrete Engineering Company, Limited
LEVER STREET, MANCHESTER.
LONDON, LIVERPOOL, MIDDLESBROUGH, GLASGOW.
Lattice System
ADVERTISEMENTS
XI
Devolving Shovels
Type "B" Erie Shovel on Road Work.
Why the ERIE Shovel pays fine profits on road work
BIG OUTPUT.— Erie Shovels excavate 500 to 600 cu. yds- per day, or more, work- In shallow cuts from 6 in. in depth, through hard material such as old ma
i ordinary bank
..._ dam,300to400
cu. yds. per day, or more, leaving a perfectly level floor bottom.
TRAVELLING ABILITY.-The superior digging ability of the "ERIE" is backed up by real travelling ability. It is far ahead of other shovels in both respects- The " ERIE " climbs a 25% gradient under its own power and is easy to steer straight- It is fitted with broad Traction Wheels, crowned and rounded at the edges.
WIDE CUTS. — A floor bottom 35 ft- wide can be excavated in one operation and wagons can be loaded 23 ft. from centre of shovel, or on an 8 ft. bank.
LABOUR SAVING.— The "ERIE" will do the work of 50 men, thus effectively solving the present labour shortage.
An unequalled Steam- Shovel
Compared with hand labour, any good Steam Shovel will prove to be a Money Saver. BUT there is a lot of difference in Shovels — a difference which may amount to as much as 30 or 40 per cent, of your profits- BEFORE You BUY, IN- VESTIGATE CAREFULLY. GET THE FACTS. CHOOSE THE BEST STEAM SHOVEL
Convertible to Locomo- tive Crane
Write for Catalogues which give details of the Type " B " j-cu. yd. capacity.
NOTE— We can give early delivery.
For Road work the automatic grading apparatus ensures a uniformly even foundation.
Sole Concessionaires for the Sale of "Erie" Shovels in the British Isles:
WM. MUIRHEAD, MACDONALD WILSON & CO., LTD.
Engineers and Public Works Contractors
41 PARLIAMENT STREET, WESTMINSTER, S.W.1
'Phone : Victoria 537 three lines; Tel. Address : Amplitude, London.
xii ADVERTISEMENTS
EMPIRE STONE
ARCHITECTURAL DRESSINGS.
STAIRCASES.
FOOTWAY PAVING SLABS.
GRANOLITHIC PAVING, ETC.
REINFORCED CONCRETE CON- STRUCTION.
CONCRETE FENCE POSTS. DIRECTION POSTS. CONCRETE KERBS & CHANNELS.
EMPIRE STONE Co.
THANET HOUSE,
231 STRAND, LONDON, W.C.
ALSO AT
NARBOROUGH, WINCHESTER HOUSE,
LEICESTERSHIRE. VICTORIA SQ., BIRMINGHAM
Gerrard 8152. T. J. MCDOWELL, Managing Director.
ADVERTISEMENTS
xni
BIG Mixers are essential on big jobs, and during the last 10 years we have supplied leading contractors in all parts of the world with Mixers up to 80 cubic feet capacity.
Illustrated below is our smallest size machine — The Victoria H.M. Mixer — which for portability, efficiency and economy is unequalled.
The scope of the H.M. Mixer is far beyond that of many small machines, and when fitted with a 2 B.H.P. petrol or paraffin engine it is capable of a very considerable output.
This Mixer is designed for either hand or power drive and can be used wherever concrete is required. The machine can be moved about freely from one part of the job to another — one- man can handle it on the level and two men are sufficient on rough and uneven tracks.
The H.M. Mixer has a low feeding position and this feature saves a considerable amount of time and labour in filling the machine.
If you have experienced the need of a really efficient, portable Mixer of this nature write to-day for our catalogue M.D. 105.
(MIXER DEPARTMENT)
ll.VICTORIA ST., LONDON S.W1
" The Small Machine wilh a Large Output."
xiv ADVERTISEMENTS
Illlill
[CONCRETE!
is now used in all forms of con- struction: in important engineering undertakings, housing, roads, on the farm and estate and in the garden.
If you are interested read
I CONCRETE ANDl I CONSTRUCTIONAL 1 ! E N G I N E E R I N G 1
The officially appointed Journal of the Concrete Institute.
ISSUED MONTHLY,
Annual Subscription post free anywhere, 2 1/-. | Specimen Copy Post Free, 1/6.
FROM—
CONCRETE PUBLICATIONS, Ltd. 4 CATHERINE STREET,
ALDWYCH, W.C.2
nil
ADVERTISEMENTS
xv
THE TONKIN MIXER— Capacity 60 tons per day
MIXES
Sloppy, Wet. Semi-Dry, or Damp Con- cretes, Facing Materials, Mortar, Grout, o r Compo. equally we 1 1, and is specially adapted for mixing Ta r Macadam for Roads.
, Full particulars
from the Offices.
608 SALISBURY HOUSE, LONDON WALL, E.G. 'Phone No. : London Wall 1931 Practical demonstrations can be given at any time by appointment.
THE "AUSTRALIA" PATENT
CONCRETE BLOCK MAKING
MACHINE
is unrivalled in efficiency,
simplicity and price, is
strong, durable, fool-proof
and easily portable.
Approved by the Ministry of Health-
May be inspected in operation at
any tirre at the works,
LAVIE MEWS,
PORTOBELLO ROAD
(WEST END), W.10
Size of Block 24 x 12 by any thickness up to 4i inches.
Output by one unskilled worker, ONE per Minute.
Full particulars from
607, Salisbury House, London Wall, E.C.2.
ADVERTISEMENTS
HOLLOWAY BROS. (London), LTD.
Contractors tor ^ferroconcrete IRoafcs ano JBrtfcges*
BRIDGE WHARF, GROSVENOR ROAD, WESTMINSTER, S.W.I,
SHARP, JONES 6 Co.
PARKSTONE, DORSET.
Patentees and Manufacturers of the
AQUATITE MANHOLE BOTTOM
Complete Concrete Manholes, of any depth,
with Step-irons ready fixed, supersede Brickwork
and save much time in construction.
We hold immense stocks of
ROCK-CONCRETE TUBES
from 15 inches to 6 feet diameter for CULVERTS UNDER ROADS, SURFACE - WATER DRAINS, STORM-WATER and SEWERS.
THE OLDEST FACTORY OF CONCRETE TUBES IN THE EMPIRE. - - - ESTABLISHED 45 YEARS.
Telegrams: "Henry, Bournemouth." TelephDne: 406 Bournemouth.
ADVERTISEMENTS
xvii
END OR EITHER SIDE TIPPING BODIES OR TRAILERS
THE "CONSTABLE" TIPPING WAGON FOR SAND, GRAVEL, BALLAST, ETC.
Only one man required for tipping the heaviest loads, the discharge of which is effected in 90 seconds.
Either-side door in the case of the side tip, and the end door in the case of an end tip, on the body being raised, is released and remains in its normal position out of the way, avoiding all obstruction to the material being discharged, and allowing a perfectly free outlet. The material is tipped
entirely clear of the wheels. The Constable Tipping Bodies have been supplied to , or are on order for,
the following Councils amongst others: —
Barrow. Glasgow (4). Maidstone. Bedfordshire.
Bo'ness. Hull. Manchester. Cumberland.
Brighton (8). Kettering. Newport. Dumbartonshire.
Cheltenham. Leeds. West Ham. Dumfriesshire.
Croydon. Leicester. Wood Green. Stirlingshire.
Derby. Lerwick. Aberdeenshire. Warwickshire.
Liverpool. Ayrshire.
The British Government and the Government of France. Please send for Booklet No. 21
TUKE & BELL, LTD., LICHFIELD, AND n LINCOLN'S INN FIELDS, LONDON, W.C.2
Hi ADVERTISEMENTS
WILLIAM GRIFFITHS & CO.,
LIMITED.
Hamilton House, Bishopsgate, London, E.C.2
ESTABLISHED NEARLY A CENTURY.
ENGINEERS & CONTRACTORS for the construction
of ROADWAYS & TRAMWAYS including CONCRETE FOUNDATIONS.
QUARRY OWNERS AND STONE MERCHANTS.
QUARRIES at GUERNSEY, GRIFF (Leicestershire), KIT HILL (Cornwall).
PITCHINGS, KERB, MACADAM, AND GRANITE CHIRPINGS FOR REINFORCED CONCRETE IN- SITU PAVING, ETC.
DIRECT IMPORTERS OF PAVING TIMBER.
Telegrams : "Griffiths, Stone, A\e., London." Telephones : 2496-2497, London Wall.
Wilson Lovatt & Sons, Ltd.
Clarence Street, :: WOLVERHAMPTON. ::
Telegrams :— •• Lovatt, Wolverhampton." Telephone :— 1130 (2 lines).
Government Contractors.
Every class of Engineering' Public Works executed.
ALL CLASSES OF RAILWAY AND ENGINEERING WORKS. DRAINAGE, SEWERS, WATER MAINS, ETC.
BUILDINGS OF ALL DESCRIPTIONS.
ALL CLASSES OF REINFORCED CONCRETE WORK.
CONCRETE AND MACADAM ROADS.
ADVERTISEMENTS xix
Telephone: WOODFORD 557.
W. & C. FRENCH,
Public Works Contractors, BUCKHURST HILL,
ESSEX.
FERRO-CONCRETE ROADS & BRIDGES.
Licensees for the Hennebique System.
FOUNDED 1840
Stuart's
Granolithic Co., Ltd.
63 LINCOLN'S INN FIELDS,
LONDON,
AND AT
MANCHESTER, BIRMINGHAM AND EDINBURGH.
'Grams: "Granolith." 'Phone: 5268 Hoi.
xx ADVERTISEMENTS
Patent Victoria Stone
OVER 50 YEARS' WEAR IN LONDON.
Large stocks of well matured paving for immediate delivery in sizes to suit any footpath.
Kerb and Channelling also stocked in large quantities.
All kinds of Architectural Stonework suitable for Housing Schemes can be supplied.
Works:—
STRATFORD MARKET, ESSEX, and GROBY QUARRIES, LEICESTERSHIRE.
The Patent Victoria Stone Co., Ltd.
11, 12 & 13 HAMILTON HOUSE, BISHOPSGATE, E.C.2
Telegraphic Address : Victoria Stone, Ave., London. Telephone : London Wall 2866.
CONCRETE
COTTAGES
Small Garages and Farm Buildings
Deals exhaustively with materials and methods of construction
DESIGNS for COTTAGES
Numbers of Illustrations and Plans
5/- NET. By Post 5/9
FROM
CONCRETE PUBLICATIONS, LTD.,
4 CATHERINE STREET, ALDWYCH, W.C.2.
ADVERTISEMENTS
xxi
FOR
PERFECT CONCRETE
use the brands
PORTLAND CEMENT
manufactured by
THE ASSOCIATED PORTLAND CEMENT MANUFACTURERS, LIMITED.
THE BRITISH PORTLAND CEMENT MANUFACTURERS, LIMITED
MARTIN EARLE& COMPANY, LIMITED
THE WOULDHAM CEMENT COMPANY, LIMITED.
'FERROCRETE'
Specially prepared
for concrete
specialists.
T"
Correspondence to be addressed to the selling organization : THE CEMENT MARKETING COMPANY LTD.
8 LLOYDS AVENUE, LONDON, E.G. 3.
Telephone: Avenue 5690. Telegrams: "Portland, Fen, London."
xx
ADVERTISEMENTS
By Appointment to H.M. King George V.
By Appointment to the late King Edward VII.
LEAD SEALED
PELICAN BRAND
OF
EARLE'S CEMENT
m
ROBSON'S PORTLAND CEMENT
MANUFACTURED BY
G. & T. EARLE, LIMITED 1
(Established over a Century)
WILMINGTON, HULL.
!
I |
I
ADVERTISEMENTS
xxni
The SOUTH WALES PORTLAND
CEMENT and LIME CO., LTD.,
PENARTH, SOUTH WALES
ESTABLISHED 1888.
CAPACITY 3,000 TONS WEEKLY
Cement Works:—
PENARTH. MITCHELDEAN. BRIDGWATER
Lime Works:—
PENARTH.
BRIDGEND.
Telephone : PENARTH 299, 300. Telegrams : " CEMENT, PENARTH."
BRIDGWATER, 142. "CEMENT, BRIDGWATER.'
BRIDGEND, 112. "LIME, BRIDGEND."
Manufacturers of —
BEST PORTLAND CEMENT ABERTHAW LIME— LUMP & GROUND.
ARTIFICIAL STONE
Brands—
SEVERN— DRAGON— COLOSSUS
Our Cement is guaranteed to readily comply with all the requirements of the BRITISH STANDARD SPECIFICATION of AUGUST, 1920.
Our DRAGON BRAND PORTLAND CEMENT— medium or slow setting —is remarkably quick hardening and is pre-eminently suitable for RE- INFORCED CONCRETE WORK. Being especially well ground it has an unusually large percentage of flour, and is very economical in use.
ON ADMIRALTY AND WAR OFFICE LISTS.
xxiv ADVEBTISEMENTS
THE
Stone Court Chalk, Land & Pier Co., Ltd.
STONE COURT,
GREENHITHE, KENT.
Telegrams: " Stone Court Co., Greenhi the." Telephone: Dartford 150
Pure White Chalk
(Block or Small).
Washed Pit Ballast and Sand
Crushed to the following Grades : PIT BALLAST - 1 in. down.
3 •
SAND -' - - I in. ,','
WASHED and CRUSHED PIT BALLAST and SAND IS HARD, ANGULAR and WELL GRADED, and MAKES the
BEST AGGREGATE FOR CONCRETE.
Deep Water Loading Jetty on River Thames, and Rail connection to S.E. & C. Rly.
London Office: SOGresham Street, Bank, London, E.C.2.
ADVERTISEMENTS
Unique (Bolleetion
When in London
DO NOT FAIL
to pay a visit to the
PERMANENT EXHIBITION OF Concrete Products
at 143, Grosvenor Road, S.W.I
(Near Vauxhall Bridge).
OPEN DAILY (Saturdays excepted), 10 a.m. to 4 p.m. ADMISSION FREE.
This collection, the only one of its kind in the King- dom, comprises over 300 examples illustrating the great variety of ways in which Concrete can be employed by Municipal and County Authorities and Railway Companies, in Public Works, and also on the Estate and Farm, and in the Home and Garden.
This Exhibition has been arranged by
THE CONCRETE UTILITIES BUREAU
35, Great St. Helens, London, E.C.3. Tel.: Avenue 5422,
XXVI
ADVERTISEMENTS
The World's Most Efficient and Durable
CONCRETE MIXERS
In models & sizes to profitably meet all needs
Ransome Special Road Concrete Mixer, which eliminates the faults of all the other Road Mixers and has advantages of its own. This is the RELIABLE Road Mixer.
VY^HEN purchasing Concrete Mixers remember this : Ransomes are the largest manufacturers of Quality Concreting Equipment in Europe, and the efficiency and substantiality of Ransome Equipment make Ransome Mixers preferred all over the world by the most experi- enced users. For safety's sake, for efficiency's sake, for economy s sake, have a genuine British Ransome. The Ransome may cost a little more, but it outwears two or three of the cheap imported kind, and turns it out better, quicker and cheaper all the time !
Write for these Catalogues :
No. 7. Special Road Concrete Mixer.
No. 151. General Concrete Mixers.
No. 13. Concrete Hoisting and Placing Plant.
No. 11. Concrete Tip-Carts.
RANSOME MACHINERY CO. (1920), LTD. Dcpt. V. 14-16 Grosvcnor Gardens, LONDON, S.W.I
Telephone : Victoria 8060. Telegrams : Ransomaco, Sowest, London.
Contractors to the principal Governments, Public Bodies and Industrial Concerns of the World.
INDEX TO ADVERTISEMENTS
PAGE
Allied Machinery Co., Ltd. ...... ii
Associated Portland Ceriient Manufacturers, Ltd. . . xxi
"Australia" Patent Concrete Block-Making Machine . xv
British Portland Cement Manufacturers, Ltd. . . . xxi
Cement Marketing Co., Ltd. ...... xxi
Concrete and Constructional Engineering . . . xiv
Concrete Cottages ....... xx
Concrete Exhibition ....... xxv
Concrete Utilities Bureau ...... xxviii
Earle, G. & T., Ltd xxii
Empire Stone Co., Ltd. ....... xii
Expanded Metal Co., Ltd. ...... vii
French, W. & C xix
Gaston Limited ........ iii
Griffiths, William, & Co., Ltd xviii
Holloway Bros. (London), Ltd. ..... xvi
Indented Bar and Concrete Engineering Co., Ltd. . . viii
Johnson's Reinforced Concrete Engineering Co., Ltd. . x
Martin Earle & Co., Ltd xxi
Muirhead, Wm., Macdonald Wilson & Co., Ltd. . . xi
Patent Victoria Stone Co., Ltd. ..... xx
Ransome Machinery Co. (1920), Ltd. .... xxvi
Self-Sentering Expanded Metal Works, Ltd. ... ix
Sharp, Jones & Co. ....... xvi
South Wales Portland Cement & Lime Co., Ltd. . . xxiii
Stone Court Chalk, Land & Pier Co., Ltd. . . . xxiv
-Stothert & Pitt, Ltd xiii
Stuart's Granolithic Co., Ltd. ..... xix
Tidnams, Ltd. ........ vi
Tonkin Mixer Co. ........ xv
Tuke & Bell, Ltd ... xvii
Walker-West on Co., Ltd i
Wilson Lovatt & Sons, Ltd. ..... xviii
\\~iiiget Limited . . . . . . . iv, v
\\Ouldham Cement Co., Ltd. .... . xxi
xx vii Q
XXVI 11
ADVERTISEMENTS
The Concrete
Utilities Bureau
Is an organization formed for the purpose of rendering assistance free of charge to those in need of information or advice on the subject of CONCRETE.
The function of this Bureau is to bring before the notice of cement users and the public generally, the very large number of ways in which Concrete may be usefully, economically and successfully employed, especially with regard to what may be termed its smaller uses ; it is not intended, however, to take the place of, or enter into competition with either the architect or the engineer by giving technical advice such as a client would expect from his professional adviser.
Enquiries addressed to the Bureau, either personally or by letter, will receive prompt attention.
The following illustrated pamphlets, containing detailed instructions, may be obtained, post free, on application : —
CONCRETE.
7. Poultry Houses andPiggeries.
8. Farm Buildings.
9. Troughs and Wells.
10. Greenhouses, Garden
Frames and Root Cellars.
11. In the Home.
12. Blocks.
1 3. General.
14. Its Artistic Possibilities.
1 . Introductory.
2. How it is made.
3. Tanks and Cisterns.
4. Paths and Pavements, Kerbs
and Gutters.
5. Fence Posts, Gate Posts and
Walls.
6. Floors, Feeding Floors and
Footpaths.
THE CONCRETE UTILITIES BUREAU
35, GREAT ST. HELENS, LONDON, E.C.3
Tel.: Avenue 5422.
ANALYSIS OF ADVERTISEMENTS
Architectural Stone Work.
Empire Stone Co., Ltd.
Patent Victoria Stone Co., Ltd.
Cement.
Associated Portland Cement Manufacturers, Ltd.
British Portland Cement Manufacturers, Ltd.
Cement Marketing Co., Ltd.
G. & T. Earle, Ltd.
Martin Earle & Co., Ltd.
South Wales Portland Cement & Lime Co., Ltd.
Wouldham Cement Co., Ltd.
Concrete Fencing and Posts.
Empire Stone Co., Ltd. Tidnams, Ltd.
Concrete Kerbs and Channels.
Empire Stone Co , Ltd. Patent Victoria Stone Co., Ltd.
Concrete Machinery
Allied Machinery Co., Ltd.
"Australia" Patent Concrete Block-Making Machine Syndicate.
Gaston Limited.
Ransome Machinery Co. (1920), Ltd.
Stothert & Pitt, Ltd.
Tonkin Mixer Co.
Winget Limited.
Concrete Publications.
Concrete and Constructional Engineering. Concrete Cottages. Concrete Utilities Bureau.
Concrete Tubes, Drain Pipes, Sewers, etc.
Sharp, Jones & Co. Contractors.
W. & C. French.
William Griffiths & Co., Ltd.
Hollo way Bros. (London), Ltd.
Muirhead, Wm., Macdonald Wilson & Co., Ltd.
Stuart's Granolithic Co., Ltd.
Wilson Lovatt & Sons, Ltd.
Direction Posts.
Empire Stone Co., Ltd. Tidnams, Ltd.
xxix
xxx ANALYSIS OF ADVERTISEMENTS
Elevators, Hoisting and Placing Plant.
Allied Machinery Co., Ltd. Gaston Limited.
Ransome Machinery Co. (1920), Ltd. Winget Limited.
Manholes.
Sharp, Jones & Co. Mixers.
Allied Machinery Co., Ltd.
Gaston Limited.
Ransome Machinery Co. (1920), Ltd.
Stothert & Pitt, Ltd.
Tonkin Mixer Co.
Winget Limited. Paving Slabs, etc.
Empire Stone Co., Ltd.
Patent Victoria Stone Co., Ltd.
Stuart's Granolithic Co., Ltd.
Reinforced Concrete Construction.
Empire Stone Co., Ltd.
Holloway Bros. (London), Ltd.
Self-Sentering Expanded Metal Works, Ltd.
Stuart's Granolithic Co., Ltd.
Walker-Weston Co., Ltd.
Wilson Lovatt & Sons, Ltd. Road Material, Aggregate, etc.
Stone Court Chalk, Land & Pier Co., Ltd.
William Griffiths & Co., Ltd. Road Plant.
Allied Machinery Co., Ltd.
Gaston Limited.
Muirhead, Wm., Macdonald Wilson & Co., Ltd.
Ransome Machinery Co. (1920), Ltd.
Winget Limited.
Road Reinforcement.
Expanded Metal Co., Ltd.
Indented Bar and Concrete Engineering Co., Ltd.
Johnson's Reinforced Concrete Engineering Co., Ltd.
Self-Sentering Expanded Metal Works, Ltd.
Walker-Weston Co., Ltd. Steam Shovels.
Allied Machinery Co., Ltd.
Gaston Limited.
Muirhead, Wm., Macdonald Wilson & Co., Ltd. Tipping Wagons and Carts.
Allied Machinery Co., Ltd.
Tuke & Bell, Ltd.
Ransome Machinery Co. (1920), Ltd.
Printed in Great Britain by
Butler & Tanner
Frcme and London
THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW
AN INITIAL FINE OF 25 CENTS
WILL BE ASSESSED FOR FAILURE TO RETURN THIS BOOK ON THE DATE DUE. THE PENALTY WILL INCREASE TO SO CENTS ON THE FOURTH DAY AND TO $1.OO ON THE SEVENTH DAY OVERDUE.
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UNIVERSITY OF CALIFORNIA
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