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Full text of "The materials and manufacture of Portland cement. By Edwin C. Eckel. The cement resources of Alabama. By Eugene A. Smith"

BERKELEY 

LIBRARY 

UNIVERSITY OF 
CALIFORNIA 



EARTH 

SCIENCES 

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UNIVERSITY OF CALIFORNIA. 



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GEOLOGICAL SURVEY OF ALABAMA 

EUGENE ALLEN SMITH, State Geologist 



BULLETIN No. 8 



THE MATERIALS AND MANUFACTURE 
OF PORTLAND CEMENT 



BY 

EDWIN C, ECKEL 



THE CEMENT RESOURCES of ALABAMA 



BY 

EUGENE A. SMITH 



GEOLOGICAL SURVEY OF ALABAMA 

EUGENE ALLEN SMITH, STATE GEOLOGTST. 



BULLETIN No. 8. 



The Materials and Manufacture of Portland Cement. 



BY 

EDWIN C. ECKEL. 



The Cement Resources of Alabama, 



BY 

EUGENE A. SMITH. 



MONTGOMERY, ALABAMA 

THE BROWN PRINTING COMPANY, PRINTERS AND BINDERS 
1904 



To His Excellency, Gov. R. M. CUNNINGHAM : 

Sir : I have the honor to submit herewith Bulletin No. 8, on 
the Cement Resources of Alabama ; with Preliminary Chapters 
on the Materials and Manufacture of Portland Cement, by Mr. 
Edwin C. Eckel, of the United! States Geological Survey. 

That part of the Report relating specially to the Alabama 
occurrences was prepared by the writer in cooperation with the 
United States Geological Survey, and in slightly different form, 
has been published in Bulletin No. 225, of that Survey. The 
chapters by Mr. Eckel, which add so much to the value and 
completeness of the Bulletin, have been generously contributed 
by him. 

Our indebtedness to Senator John T. Morgan is particularly 
great, since the investigations on which this report is based, 
were undertaken mainly at his instance, and the cooperation 
above mentioned, secured through his influence. 
Very respectfully, 

EUGENE A. SMITH, 

State Geologist. 
University of Alabama, 
July I, 1904. 



GEOLOGICAL CORPS. 

EUGENE A. SMITH State Geologist. 

HENRY McCALLEY Chief Assistant. 

ROBERT S. HODGES Chemist. 

JA:\TES A. ANDERSON Assistant in Office and Museum. 

B. F. LOVELACE i ..Assistant in Coastal Plain Work. 

GEORGE N. BREWER Assistant in Coal Measures Work. 



TABLE OF CONTENTS. 



PART I THE MATERIALS AND MANUFACTURE OF PORTLAND 
CEMENT, by Edwin C. Eckel. 

CHAPTER I. 

PAGE. 

Relation of Portland to other Cements 1 

Group T Simple Cements 2 

( a) Hydrate Cements 8 

(b) Carbonate Cements 4 

High Calcium Limes 5 

Magnesian Limes 6 

Group II Complex Cements 6 

f 1. Pozzuolanic Cements . 7 

Classes of Silicate Cements. . J 2 - Hydraulic Limes 7 

\ 3. Natural Cements 8 

14. Portland Cements 9 

Natural Cements 8 

Portland Cements 10 

Puzzolan Cements . . 10 

CHAPTER II. 

Portland Cement: Definition: Composition and Constituents.... 11 

CHAPTER III. 

Raw Materials: General Considerations 15 

Origin and General Characters of Limestone 16 

Origin of Limestone 16 

Varieties of Limestone 17 

Chemical Composition of Limestone 18 

Physical Characters of Limestones 21 

Effect of heating on Limestone 21 

CHAPTER n. 

Raw Materials in Detail '. . . 22 

Argillaceous Limestone: Cement Rock 22 

Cement Rock of the Lehigh District 22 

Cement Rock in other parts of the United States 24 

Pure hard Limestone 25 



VI 

PAGE. 

Soft Limestone : Chalk 26 

Origin and General Characters '...'.'. 26 

Geographical and Geological Distribution in the 

United States 26 

Composition 27 

Fresh Water Marls 27 

Origin of Marls 28 

Geographical Distribution of Marl Deposits 29 

Composition 9<* 

Alkali Waste 30 

Blast Furnace Slag 31 

Clays and Shales 32 

Slate 33 

CHAPTER V. 

Economic Considerations and Methods of Manufacture 34 

Quarrying 34 

Mining . 35 

Dredging 35 

Cost of the Raw Material at Mill 36 

Methods of Manufacture 38 

Preparation of the Mixture for the Kiln 38 

Drying the Raw Materials 39 

Percentage of Water in the Raw Material 39 

Methods and Cost of Drying 40 

Grinding and Mixing Dry Methods 41 

Fineness of Mixture 42 

Grinding and Mixing Slag-limestone Mixtures 43 

General Methods 43 

Composition of the Slag 44 

Granulation of the Slag 44 

Drying of the Slag 45 

Grinding the Slag 45 

Composition of the Limestone 45 

Economics of using Slag-umestone Mixtures. ... 46 

Grinding and Mixing Wet Methods 47 

Composition of the Mixture 4 

Burning the Mixture 50 

Summary of Burning Process 51 

Theoretical Fuel Requirements 52 

Losses of Heat in Practice 52 

Actual Fuel Requirements and Output 53 

Effect of Composition on Burning 54 

Character of Kiln Coal 54 

Drying Coal 55 

Pulverizing Coal 55 

Total Cost of Coal Preparation 55 

Clinker Grinding: Gypsum 56 

Clinker Grinding 56 

Addition of Gypsum 57 

Constitution of Portland Cement 57 



VII 

PART II. THE CEMENT RESOURCES OF ALABAMA, by 

Eugene A. Smith 61 

CHAPTER I. 

PAGE. 

The Portland Cement Materials of Northern Alabama 61 

Available Limestones 62 

General Geology 62 

Lower Carboniferous 62 

Trenton Limestones 63 

Marbles 66 

The Clays 66 

Coal Measures 67 

Lower Carboniferous 67 

Lower Silurian and Cambrian 68 

Cretaceous 68 

Table A Analyses of Lower Carboniferous Limestones. . 71 

Table B Analyses of Trenton Limestones 72 

Table C Analyses of Crystalline Marbles 73 

Table D Analyses of Clays Paleozoic and Lower Cre- 
taceous 74 

CHAPTER IT. 

The Portland Cement Materials of Central and Southern Alabama 76 

The Selma Chalk, or Rotten Limestone 76 

Geological Horizon 76 

General Description 77 

Details of Localities 79 

Table E Analyses of Cretaceous Limestones 84 

The St. Stephens Limestone 86 

General Description 86 

Details of Localities 87 

St. Stephens 87 

Oven Bluff 88 

Localities along line of the Southern R. R 88 

Along Alabama River 89 

Between Alabama River and the Main Line of 

the Louisville & Nashville Railroad 90 

On the Main Line of the L. & N. R.R 90 

Table F Analyses of Tertiary Limestones 92 

Table G Analyses of Clays (Cretaceous and Terti- 
ary) and Cement 93 



VIII 



ILLUSTRATIONS. 

Plate I Geological Map of Alabama Frontispiece 

Plate II Caves in Limestone, below Roe's Bluff, Tombigbee 

River face p. 79 

Plate III 1 Gainesville, Tombigbee River 80 

Plate IV Jones' Bluff at Epes, looking down stream from Bridge 80 

Plate V Kil man's Bluff, below Epes, Tombigbee River 80 

Plate VI Chalk exposure at Bluff port, Tombigbee River 80 

Plate VI JL Below Jordan's Ferry, Tombigbee River 81 

Plate VIII Roe's Bluff, Tombigbee River 81 

Plate IX Bluff of Selma Chalk, Demopolis, looking up stream 

from Steamboat Landing 81 

Plate X Bluff at Demopolis, looking down stream 81 

Plate XI Hatch's Bluff, above Demopolis, on Warrior River 81 

Plate XII Alabama Portland Cement Works, at Demopolis 81 

Plate XIII-^Exposure of Selma Chalk at VanDorn Station, Ma- 

rengo County 82 

Plate XIV White Bluff, Alabama River 82 

Plate XV Elm Bluff, Alabama River 82 

Plate XVI St. Stephens Bluff, Tombigbee River 86 



rt- 




i. 



THE MATERIALS AND MANUFACTURE OE PORT- 
LAND CEMENT.* 



15Y Ei)\VIX ('. ECKEL. 



[The following paper on the raw materials and methods of manu- 
facture of Portland Cement has been prepared as the result of field 
work and other investigations carried out by the writer for the 
United States Geological Survey. Certain sections of the contribu- 
tion have appeared, in slightly different form, in Municipal Engi- 
neering during the past two years.] 

CHAPTER 1. 

THE RELATION OE PORTLAND TO OTHER 
CEMENTS. 

It seems desirable, before taking up the specific subject of 
Portland cement, to indicate the relationships existing between 
Portland and other cementing materials. These relationships, 
both as regards resemblances and differences, seem to be best 
brought out by the classification presented below. This group- 
ing is based primarily upon the amount of chemical change 
caused by the process of manufacture and use ; and secondarily 
upon the chemical composition of the cement after setting. As 
regard is paid to both technologic and commercial conside- 
rations, it would seem to be a fairly satisfactory working classi- 
fication. 

GROUP I. SIMPLE CEMENTS : Including all those cement- 
ing materials produced by the expulsion of a liquid or gas from 
the rarvv material ; and whose setting properties are due to the 

*Publishcd by permission of the Director, U. S. Geological Survey. 



simple reabsorption of the same liquid or gas and the reassump- 
tion of original composition ; the set cement being therefore simi- 
lar in composition to the raw material. 

Sub-grohp la. Hydrate C.ements : Setting properties due 
to reabsorption of water. 

Sub-group Ib. Carbonate Cements : Setting properties due 
to reabsorption of carbon dioxide. 

GROUP II. COMPLEX CEMENTS : Including all those cement- 
ing materials whose setting properties are due to the action of 
entirely new chemical compounds which were formed during 
manufacture or use ; the set cement being therefore different in 
composition from the raw material. 

Sub-group la. Silicate Cements : Setting properties due 
largely to the formation o<f silicates. 

Sub-group lib. Oxy chloride Cements: Setting properties 
due to the formation of oxychlorides. 

GROUP I SIMPLE CEMENTS. 

The cementing materials included in the present group are 
those known commercially . as ''plasters," ''hard-finishing ce- 
ments," and "limes." 

The material from which the ''plasters" and "hard-finishing 
cements" are derived is gypsum, a hydrous calcium sulphate ; 
while the limes are derived from limestone, which is essentially 
calcium carbonate, though usually accompanied by greater or 
less amounts of magnesium carbonate. 

On heating gypsum to a certain temperature, the raw mater- 
ial parts readily with much of its water, leaving an almost 
anhydrous calcium sulphate, known commercially as plaster-of- 
Paris. On exposing this plaster to water, it re-hydrates, and 
again takes the composition of the gypsum from which it was 
derived. 

In like manner limestone, on being sufficiently heated, gives 
off its carbon dioxide, leaving calcium oxide or "quicklime." 
This, on exposure to moisture and air carrying carbon dioxide, 
reabsorbs carbon dioxide and reassumes its original composi- 
tion, calcium carbonate. 

The cementing materials included in this group, therefore, 



while differing in composition and properties, agree in certain 
important points. They are all manufactured by heating a 
natural raw material sufficiently to remove much or all of its 
water or carbon dioxide; and, in all, the setting properties of 
the cementing material are due to the fact that, on exposure to 
the water or carbon dioxide which has thus been driven off, the 
cement reabsorbs the previously expelled liquid o>r gas, and re- 
assumes the chemical composition of the raw material from 
which it was derived. 

Plaster-of-Paris, after setting, is not chemically different from 
the gypsum from which it was derived ; while if the sand, added 
to avoid shrinkage, be disregarded, hardened lime- mortar is 
nothing more or less than an artificial limestone. 

Sub-group la. Hydrate Cements. 

The materials here included are known in commerce as "plas- 
ter-of-Paris," "cement plaster," "Keene's cement," "Parian ce- 
ment/' etc. All of these hydrate cements are based upon one 
raw material, gypsum. The partial dehydration of pure gyp- 
sum produces plaster-of-Paris. By the addition of gypsum, 
either by nature or during manufacture, of relatively small 
amounts of other materials ; or by slight variations in the pro- 
cesses of manufacture, the time of setting, hardness, and other 
important technical properties of the resulting plaster can be 
changed to a sufficient degree to warrant separate naming and 
descriptions of the products. 

P>oth the technology and the chemistry of the processes in- 
volved in the manufacture of the hydrate cements are simple. 
The mineral gypsum, when pure, is a hydrous sulphaite of limie, 
of the formula CaSO4, 2H2O, corresponding to the composi- 
tion calcium sulphate 79.1%, water 20.9%. Gypsum, as mined, 
rarely even approximates to this ideal composition, its impurities 
often amounting to 25% or even more. These impurities, chiefly 
clayey materials and fragments of quartz and limestone, often 
exercise an appreciable effect upon the properties of the plaster 
resulting from burning such impure gypsum. 

On burning pure gypsum at a relatively low temperature 
(35O-4OO F.) much of its water of combination is driven off, 
leaving a partially dehydrated lime sulphate. This, when 
ground, is plaster of Paris, or if it either naturally or artificial- 



ly contains certain impurities, it is called "cement plaster." 
When either plaster of Paris or cement plaster are mixed with 
water, the percentage of water which was driven of! during 
calcination is reabsorbed, and the mixture hardens, having 
again becomes a hydrous sulphate o<f lime. The processes involv- 
ed in the manufacture and setting of the dead-burned plasters 
and hard-finish plasters are slightly more complicated, but the 
reactions involved are of the same general type. 

Sub-group Ib. Carbonate Cements. 

The cementing materials falling in the present sub-group are 
oxides, derived from natural carbonates by the application of 
heat. On exposure, under proper conditions, to any source of 
carbon dioxide, the cementing material recorbonates and ''sets.'' 
In practice the carbon dioxide required for setting is obtained 
simply by exposure of the mortar to the air. In consequence 
the set of these carbonate cements, as commonly used, is very 
slow (owing to the small amount of carbon dioxide which can 
be taken up from ordinary air) ; and, what is more important 
from an engineering point of view, none of the mortar in the 
interior of a wall ever acquires hardness, as only the exposed 
portions have an opportunity to absorb carbon dioxide. From 
the examination of old mortars it has been thought probable 
that a certain amount of chemical action takes place between the 
sand and the lime, resulting in the formation of lime silicates ; 
but this effect is slight and of little engineering importance com- 
pared with the hardening which occurs in consequence of the 
reabsorption of carbon dioxide from the air. 

Limestone is the natural raw material whose calcination fur- 
nishes the cementing materials of this group. If the limestone 
be an almost pure calcium carbonate it will, on calcination, yield 
calcium oxide or "quicklime." If, however, the limestone 
should contain any appreciable percentage of magnesium car- 
bonate, the product will be a mixture of the oxides of calcium 
and magnesium commercially known as magnesian lime. A brief 
sketch of the mineralogic relationships of the various kinds of 
limestone, in connection with the chemistry of lime-burning, 
will be of service at this point of the discussion. 

Pure limestone has the composition of the mineral calcite, 
whose formula is CaCO3, corresponding to the composition 



calcium oxide 56%, carbon dioxide, 44%. In the magnesian 
limestones part of this calcium carbonate is replaced by magne- 
sium carbonate, the resulting rock therefore having a formula of 
the type X CaCC>3, Y MgCC)3. This replacement may reach 
the point at which the rock has the composition of the mineral 
dolomite an equal mixture of the two carbonates, with the 
formula CaCO3, MgCO3, corresponding to the composition 
calcium oxide 30.43%, magnesium oxide, 21.74%, car- 
bon dioxide, '47.83%. Limestones may therefore occur 
with any intermediate amount of magnesium carbon- 
ate, and the lime which they produce on calcination 
will carry corresponding percentages of magnesium ox- 
ide, from o% to 21.74%. Commercially those limes which 
carry less than 10% of magnesium oxide are, for building pur- 
poses, marketable as "pure limes"; while those carrying more 
than that percentage will show sufficiently different properties 
to necessitate being marketed as "magnesian limes." 

Aside from the question of magnesia, a limestone may con- 
tain a greater or lesser amount of impurities. Of these the most 
important are silica (SiO2), alumina (A12O3), and iron oxide 
(Fe2O3). These impurities, if present in sufficient quantity, 
will materially affect the properties of the lime produced, as 
w r ill be noted under the heads of Hydraulic Limes and Natural 
Cements. 

The Carbonate Cements may be divided into tw r o classes : 

1 i ) High calcium limes ; 

(2) Magnesian limes. 

High Calcium Limes, On heating a relatively pure carbon- 
ate of lime to a sufficiently high degree, its carbon dioxide is 
driven off, leaving calcium oxide (CaO) or "quicklime." 
Under ordinary conditions, the expulsion of the carbon dioxide 
is not perfectly effected until a temperature of 925 C. is 
reached. The process is greatly facilitated by blowing air 
through the kiln, or by the injection of steam. On treating 
quicklime with water, "slacking" occurs, heat being given off, 
and the hydrated calcium oxide (CaH2O2) being formed. The 
hydrated oxide will, upon exposure to the atmosphere, slowly 
reabsorb sufficient carbon dioxide to reassume its original com- 
position as lime carbonate. As this reabsorption can take place 



6 

only at points where the mortar is exposed to the air, the ma- 
terial in the middle of thick walls never becomes recarbonated. 
In order to counteract the shrinkage which \vould otherwise 
take place during the drying of the mortar, sand is invariably 
added in the preparation of lime mortars, and as noted above, 
it is probable that certain reactions take place between the lime 
and the sand. Such reactions, however, though possibly con- 
tributing somewhat to the hardness of old mortars, are only in- 
cidental and subsidiary to the principal cause of" setting, recar- 
bonation. The presence of impurities in the original limestone 
affects the character and value of the lime produced. Of these 
impurities, the presence of silica and alumina in sufficient quan- 
tities will give hydraulic properties to the resulting limes ; such 
materials will be discussed in the next group as Hydraulic 
Limes and Natural Cements. 

Magnesian Limes. The presence of any considerable 
amount of magnesium carbonate in the limestone from which a 
lime is obtained has a noticeable effect upon the character of the 
product. If burned at the temperature usual for a pure lime- 
stone, maignesian limestones give a lime which slakes slowly 
without evolving much heat, expands less in slaking, and sets 
more rapidly than pure lime. To this class belongs the well 
known and much used limes of Canaan (Conn.) ; Tuckahoe, 
Pleasantville and Ossining, (N. Y.) ; various localities in New 
Jersey and Ohio; Cedar Hollow (Penn.), and Chewacla (Ala.) 
Under certain conditions of burning, pure magnesian limestone 
yields hydraulic products, but in this case, as in the case of the 
product obtained by burning pure magnesite, the set seems to 
be due to the formation of a hydroxide rather than of a carbon- 
ate. Magnesian limestones carrying sufficient silica and alum- 
ina will give, on burning, a hydraulic cement falling in the next 
group under the head of Natural Cements. 

GROUP II--COMPLEX CEMENTS. 

The cementing materials grouped here as Silicate or Hydrau- 
lic Cements, include all those materials whose setting proper- 
ties are due to the formation of new compounds, during manu- 
facture or use, and not to the mere reassumption of the original 
composition of the material from which the cement was made. 
These new compounds may be formed either bv chemical change 



during manufacture or by chemical interaction, in use, of mater- 
ials which have merely been mechanically mixed during manu- 
facture. 

In the class of silicate cements are included all the materials 
commonly known as cements by the engineer (natural cements, 
Portland cement, pozzuolanic cements), together with the hy- 
draulic limes. 

Though differing widely in raw material, methods of manu- 
facture and properties, the silicate cements agree in two promi- 
nent features: they are all hydraulic (though in very different 
degrees) ; and this property of hydraulicity is, in all, due largely 
or entirely to the formation of tri-calcic silicate (3 CaO SiO2). 
Other silicates of lime, as well as silico-aluminates, may also be 
formed ; but they are relatively unimportant, except in certain 
of the natural cements and hydraulic limes where the lime- 
aluminates may be of greater importance than is here indicated. 
This will be recurred to in discussing the groups named. 

The silicate cements are divisible, on technologic grounds, 
into four distinct classes. The. basis for this division is given 
below. It will be seen that the first named of these classes (the 
pozzuolanic cements) differs from the other three very markedly 
inasmuch as its raw materials are not calcined after mixture; 
while in the last three classes the raw materials are invariably 
calcined after mixture. The four classes differ somewhat in 
composition, but more markedly in methods of manufacture and 
in the properties of the finished cements. 

Classes of Silicate Cements. 

/. Pozswolcenic* Cements : Produced by the mechanical 
mixture, without calcination, of slaked lime and a silico-alumin- 

ous- material (the latter being usually a, volcanic ash or blast- 
furnace slag.) 

2. Hydraulic Limes : Produced by the calcination, at a tem- 
perature not much higher than that of decarbonation, of a silice- 
ous limestone so high in lime carbonate that a considerable 
amount of free lime appears in the finished product. 



*Also written Puzzolan. 



8 

j. Natural Cements : Produced by the calcination, at a tem- 
perature between those of decarbonation and clinkering, of a 
siliceous limestone (which may also carry notable amounts of 
'alumina and of magnesium carbonate) in which the lime car- 
bonate is so low, relatively to the silica and alumina, that little 
or no free lime appears in the cement. 

4. Portland Cements: Produced by the calcination, at the 
temperature of semi-vitref action ("clinkering") of an artificial 
mixture of calcareous with silico-aluminous materials, in the 
proportion of about three parts of lime carbonate to one part of 
clayey material. 

NATURAL CEMENTS. 

Natural cements are produced by burning a naturally impure 
limestone, containing from 15 to 40 per cent, of silica, alumina, 
and iron oxide. This burning takes place at a comparatively 
low temperature, about that of ordinary lim<e burning. The 
operation can therefore be carried on in a kiln closely resemb- 
ling an ordinary lime kiln. During the burning the carbon di- 
oxide of the limestone is almost entirely driven off, and the 
lime combines with the silica, alumina, and iron nxide. forming 
a mass containing silicates, aluminates, and ferrites of lime. In 
case the original limestone contained much magnesium carbon- 
ate, the burned rock will also contain a corresponding amount 
of magnesia and magnesian compounds. 

After burning, the burned mass will not slack if water be 
added. It is necessary, therefore, to giind it quite finely. After 
grinding, if the resulting powder (-natural cement) be mixed 
with water it will harden Vapidly. This hardening or setting 
will also take place under water. The natural cements differ 
from ordinary limes in two noticeable ways: 

1 i ) The burned mass does not slack on the addition of water. 

(2) After grinding, the powder has hydraulic properties, 
i. e., if properly prepared, it will set under water. 

Natural cements are quite closely related to both hydraulic 
limes on the one hand, and Portland cement on the other, agree- 
ing with both in the possession of hydraulic properties. They 
differ from hydraulic limes, however, in that the burned natural 
cement rock will not slake when water is poured on it. 



9 

The natural cements differ from Portland cements in the fol- 
lowing important particulars : 

(1) Natural cements are not made by burning carefully pre- 
pared and finely ground artificial mixtures, but by burning 
masses of natural rock. 

(2) Natural cements, after burning and grinding, are usu- 
allv yellow to brown in color and light in weight, their specific 
gravity being about 2.7 to 2.9 ; while Portland cement is com- 
monly blue to gray in color and heavier, its specific gravity 
ranging from 3.0 to 3.2. . 

(3) Natural cements are always burned at a lower tempera- 
ture than Portland, and commonly at a much lower temperature, 
the mass of rock in the kiln never being heated high enough to 
even approach the fusing or clinkering point. 

(4) In use, natural cements set more rapidly than Portland 
cement, but do not attain such a high ultimate strength. 

(5) In composition, while Portland cement is a definite pro- 
duct whose percentages of lime, silica, alumina and iron oxide 
vary only between narrow limits, various brands of natural ce- 
ments will show very great differences in composition. 

The material utilized for natural cement manufacture is in- 
variably a clayey limestone, carrying from 13 to 35 per cent, of 
clayey material, of which 10 to 22 per cent, or so is silica, while 
alumina, and iron oxide together may vary from 4 to 16 per 
cent. It is the presence of these clayey materials which give the 
resulting cement its hydraulic properties. Stress is often care- 
lessly or ignorantly laid on the fact that many of our best known 
natural cements carry large percentages of magnesia, but it 
should, at this date, be realized that magnesia (in natural ce- 
ments at least] may be regarded as being almost exactly inter- 
changeable with lime, so far as the hydraulic properties of the 
product are concerned. The presence of magnesium carbonate 
in a natural cement rock is then merely incidental, while the 
silica, alumina and iron oxide are essential. The 30 per cent, or 
so of magnesium carbonate which occurs in the cement rock of 
the Rosendale District, N. Y., could be replaced by an equal 
amount of lime carbonate, and the burnt stone would still give 
a hydraulic product. If, however, the clayey portion (silica, 
alumina, and iron oxide) of the Rosendale rock could be re- 
moved, leaving only the magnesium and lime carbonates, the 



10 

burnt rock would lose all of its hydraulic properties and would 
yield simply a magnesian lime. 

This point has been emphasized because many writers on the 
subject have either explicitly stated or implied that it is the mag- 
nesian carbonate of the Rosendale, Akron, Louisville, Utica, 
ar?d Milwaukee rocks that causes them to yield a natural cement 
on burning. 

PORTLAND CEMENT. 

Portland cement is produced by burning a finely ground arti- 
ficial mixture containing essentially lime, silica, alumina, and 
iron oxide, in certain definite proportions. Usually this combi- 
nation is made by mixing limestone or marl with clay or shale, 
in which case about three times as much of the lime carbonate 
should be present in the mixture as of the clayey materials. 
The burning takes place at a high temperature, approaching 
3,000 F., and must, therefore, be carried on in kilns of special 
design and lining. During the burning, combination of the lime 
with silica,, alumina, and iron oxide takes place. The product 
of the burning is a semi-fused mass called clinker, and consist- 
ing of silicates, aluminates, and ferrites of lime in certain defi- 
nite proportions. This clinker must be finely ground. After 
such grinding the powder ( Portland cement) will set under 
water. 

As noted above, under the head of Natural Cements, Port- 
land cement is blue to gray in color, with a specific gravity of 
3.0 to 3.2, and sets more slowly than natural cements, but soon 
attains a higher tensile strength. 

PUZZOLAN CEMENTS. 

The cementing materials included under this name are made 
by mixing powdered slaked lime with either a volcanic ash or a 
blast-furnace slag. The product is therefore simply a me- 
chanical mixture of two ingredients, as the mixture is not burn- 
ed at any stage of the process. After mixing, the mixture is 
finely ground. The resulting powder (Puzzolan cement) will 
set under water. 

Puzzolan cements are usually light bluish to light yellow in 
color, and of lower specific gravity and less tensile strength 
than Portland cement. They are better adapted to use under 
water than to use in air. 



CHAPTER 2. 

PORTLAND CEMENT: DEFINITION, COMPOSITION 
AND CONSTITUTION. 

In the following section various possible raw materials for 
Portland cement manufacture will be taken up, and their rela- 
tive suitability for such use will be discussed. In order that the 
statements there made may be clearly understood, it will be 
necessary to preface this discussion by a brief explanation re- 
garding the composition and constitution of Portland cement. 

Use of term Portland. While there is a general agreement 
of opinion as to what is understood by the term Portland ce- 
ment, a few points of importance are still open questions. The 
definitions of the term given in specifications are in consequence 
often vague and unsatisfactory. 

It is agreed that the cement mixture must consist essentially 
of lime, silica, and alumina in proportions which can vary but 
slightly ; and that this mixture must be burned at a temperature 
which will give a semi-fused product a "clinker." These 
points must therefore be included in any satisfactory definition. 
The point regarding which there is a difference of opinion is 
wnether or not cements made by burning a natural rock can 
be considered true Portlands. The question as to whether the 
definition of Portland cement should be drawn so as to include 
or exclude such products is evidently largely a matter of con- 
vention ; but, unlike most conventional issues, the decision has 
very important practical consequences. The question at issue 
may be stated as follows : 

If we make artificial mixture of the raw materials and a very 
high degree of burning the criteria on which to base our defini- 
tion, we must in consequence of that decision exclude from the 
class of Portland cements certain well known products, manu- 
factured at several points in France and Belgium by burning a 
natural rock, without artificial mixture, and at a considerably 
lower temperature than is attained in ordinary Portland cement 
practice. These "natural Portlands" of France and Belgium 



12 

have always been considered Portland cements by the most criti- 
cal authorities, though all agree that they are not particularly 
high grade Portlands. So that a definition, based upon the cri- 
teria above named, will of necessity exclude from our class of 
Portland cements some very meritorious products. 

There is no doubt that in theory a rock could occur, contain- 
ing lime, silica, and alumina in such correct proportions as to 
give a good Portland cement on burning. Actually, however, 
such a perfect cement rock is of extremely rare occurrence. As 
above stated, certain brands of French and Belgian "Portland" 
cements are made from such natural rocks, without the addition 
of any other material ; but these brands are not particularly high 
grade, and in the better Belgian cements the composition is cor- 
rected by the addition of other materials to the cement rock, be- 
fore burning. 

The following definition of Portland cement is of importance 
because of the large amount of cement which will be accepted 
annually under the specifications* in which it occurs. It is also 
of interest as being the nearest approach to an official govern- 
ment definition of the material that we have in this country : 

"By a Portland cement is -meant the product obtained from 
the heating or calcining up to incipient fusion of intimate mix- 
tures, either natural or artificial, of argillaceous with calcare- 
ous substances, the calcined product to contain at least 1.7 times 
as much of lime, by weight, as of the materials which give the 
lirne its hydraulic properties, and to be finely pulverized after 
said calcination, and thereafter additions or substitutions for 
the purpose only of regulating certain properties of technical 
importance to be allowable to not exceeding 2 per cent, of the 
calcined product." 

It will be noted that this definition does not require pulveriz- 
ing or artificial mixing of the materials prior to burning. It 
seems probable that the Belgian "natural Portlands" were kept 
in mind when these requirements were omitted. In dealing 
with American made cements, however, and the specifications 
are headed "Specifications for American Portland Cement," it 
is a serious error to> omit these requirements. No true Portland 
cements are at present manufactured in America from natural 

*Professional Paper, No. 28, Corps of Engineers, U.S.A., p. 30. 



J3 

mixtures, without pulverizing and artificially mixing the mater- 
ials prior to burning. Several plants, however, have placed on 
the market so-called Portland cements made by grinding up to- 
gether the underburned and overburned materials formed dur- 
ing the burning of natural cements. Several of these brands 
contain from 5 to 15 per cent, of magnesia; and under no cir- 
cumstances can they be considered true Portland cements. 

In view of the conditions above noted, the writer believes that 
the following definition will be found more satisfactory than the 
above quoted : 

Definition of Portland cement. Portland cement is an artifi- 
cuil product obtained by finely pulverizing the clinker produced 
by burning to semi-fusion an intimate mixture of finely ground 
calcareous and argillaceous material, this mixture consisting 
approximately of one part of silica and alumina to three parts 
of carbonate of lime (or an equivalent amount of lime oxide.) 

Composition and Constitution. Portland cement may be said 
to tend toward a composition approximating to pure tricalcic 
silicate (3 CaO, SiCte) which would correspond to the propor- 
tion CaO 73-6%, SiO2 26.4%. As can be seen, however, from 
the published analyses, actual Portland cements as at present 
made differ in composition very markedly from this. 
Alumina is always present in considerable quantity, forming 
with part of the lime, the dicalcic aluminate (2 CaO, SiO2). 
This would give, as stated by Newberry, for the general for- 
mula of a pure Portland. 

X (3 CaO, SiO2), Y (2 CaO, AbOs). 

But the composition is still further complicated by the pres- 
ence of accidental impurities, or intentionally added ingredi- 
ents. These last may be simply adulterants, or they may be 
added to serve some useful purpose, Calcium sulphate is a type 
of the latter class. Tt serves to retard the set of the cement, and, 
in small quantities, appears to have no injurious effect which 
would prohibit its use for this purpose. In dome kilns, suffi- 
cient sulphur trioxide is generally taken up by the cement from 
the fuel gases to obviate the necessity for the later addition of 
calcium sulphate, but in the rotary kiln its addition to the ground 
cement, in the form of either powdered gypsum or plaster-of- 
Paris, is a necessitv. 



14 

Iron oxk';~, within reasonable limits, seems to. act PS a substi- 
tute for alumina, and the two may be calculated together. Mag- 
nesium carbonate is rarely entirely absent from limestones or 
clays, and magnesia is therefore almost invariably present in the 
finished cement. Though magnesia, when magnesium carbon- 
ate is burned at low temperature, is an active hydraulic material, 
it does not combine with silica or alumina at the clinkering heat 
employed in Portland cement manufacture. At the best it is an 
inert and valueless constituent in the cement ; many regard it as 
positively detrimental in even small amounts, and because of 
this feeling manufacturers prefer to carry it as low as possible. 
Newberry has stated that in amounts of less than 3^% it i c 
harmless, and American Portlands from the Lehigh district 
usually reach well up toward that limit. In European practice 
it is carried somewhat lower. 



CHAPTER :J. 

RAW MATERIALS. GENERAL CONSIDERATIONS. 

For the purposes of the present chapter, it will be sufficiently 
accurate to consider that a Portland cement mixture, when ready 
for burning, will consist of about 75 per cent, of lime carbonate 
(Ca CO3) ancl 20 per cent, of silica (SiO2), alumina (A12O3) 
and iron oxide (Fe2C>3) together, the remaining 5 per cent, in- 
cluding any magnesium carbomate, sulphur and alkalies that 
may be present. 

The essential elements which enter into this mixture, lime, 
silica, alumina and iron, are all abundantly and widely dis- 
tributed in nature, occurring in different forms in many kinds 
of rocks. It can, therefore, be readily seen that, theoretically, 
a satisfactory Portland cement mixture could be prepared by 
combining, in an almost infinite nurnber of ways and propor- 
tions, many possible raw materials. Obviously, we, too, might 
expect to find perfect graduations in the artificialness of the 
mixture, varying fron\the one extreme where a natural rock of 
absolutely correct composition was used to the other extreme 
where two or more materials, in nearly equal amounts, are re- 
quired to make a mixture of correct composition. 

The almost infinite number of raw materials which are theo- 
retically available are, however, reduced to a very few in prac- 
tice under existing commercial conditions. The necessity for 
making the mixture as cheaply as possible rules out of conside- 
ration a large number of materials which would be considered 
available if chemical composition was the only thing to be taken 
into account. Some materials otherwise suitable are too scarce ; 
some are too difficult to pulverize. In consequence, a compara- 
tively few combinations of raw materials are actually used in 
practice. 

In certain localities deposits of argillaceous (clayey) lime- 
stone or "cement rock" occur, in which the lime, silica, alumina 
and iron oxide exist in so nearly the proper proportions that 
only a relatively small amount (say 10 per cent, or so) of other 
material is required in order to make a mixture of correct com- 
position. 



16 

In the majority of plants, however, most or all of the neces- 
sary lime is furnished by one raw material, while the silica, alu- 
mina and iron oxide are largely or entirely derived from another 
raw material. The raw material which furnished the lime is 
usually natural, a limestone, chalk or marl ; but occasionally 
an artificial product is used, such as the chemically precipitated 
lime carbonate which results as waste from alkali manufacture. 
The silica, alumina and iron oxide of the mixture are usually 
derived from clays, shales or slates ; but in a few plants blast- 
furnace slag is used as the silico-aluminous ingredient in the 
manufacture of true Portland cement. 

The various combinations of raw material which are at pres- 
ent used in the United States in the manufacture of Portland 
cement may be grouped under six heads. This grouping is as 
follows : 

T. Argillaceous limestone (cement rock) and pure limestone. 

2. Pure hard limestone and clay or shale. 

3. Soft chalky limestone and clay. 

4. Marl and clay. 

5. Alkali waste and clay. 

6. Slag and limestone. 

ORIGIN AND GENERAL CHARACTERS OP LIMESTONE. 

The cement materials which are described in the four follow- 
ing sections as argillaceous limestone or cement rock, pure hard 
limestone, chalk, and marl, though differing sufficiently in their 
physical and economic characters to be discussed separately 
and under different names, agree in that they are all forms of 
limestone. The origin, chemical composition, physical charac- 
ters, and properties of limestone will, therefore, be briefly taken 
up in the present chapter to serve as an introduction to the more 
detailed statements concerning the various types of limestone to 
be found in the succeeding chapters. 

Origin of limestones* Limestones have been formed large- 
ly by the accumulation at the sea bottom of the calcareous re- 

*For a more detailed discussion of this subject the reader will do 
well to consult Chapter VIII of Prof. J. F. Kemp's "Handbook of 
Rocks." 




s*\\*> F 
t 

( UNIVERSITY 

V 0> 

17 

mams of such organisms as the foraminifera, corals, and mol- 
lusks. Most of the thick and extensive limestone deposits of 
the United States were probably deep-sea deposits formed in 
this way. Many of these limestones still show the fossils of 
which they were formed, but in others all trace of organic ori- 
gin has been destroyed by the fine grinding to which the shells 
and corals were subjected before their deposition at the sea- 
bottom. It is probable also that part of the calcium carbonate 
of these limestones was a purely chemical deposit from solution, 
cementing the shell fragments together. 

A far less extensive class of limestones though important in 
the present connection' owe their origin to the indirect action of 
organisms. The "marls," so important today as Portland ce- 
ment materials, fall in this class. As the class is of limited ex- 
tent, however, its method of origin may be dismissed here, but 
will be described later in the section on Marls. 

Deposition from solution by purely chemical means has uns- 
doubtedly given rise to numerous limestone deposits. When 
this deposition took place in caverns or in the open air, it gave 
rise to onyx deposits and to the "travertine marls" of certain 
Ohio and other localities ; when it took place in isolated portions 
of the sea through the evaporation of the sea water it gave rise 
to the limestone beds which so frequently accompany deposits 
of salt and gypsum. 

Varieties of limestone. A number of terms are in general 
use for the different varieties of limestone, based upon differ- 
ences of origin, texture, composition, etc. The more important 
of these terms will be briefly defined. 

The marbles are limestones which, through the action of heat 
and pressure, have become more or less distinctively crystalline. 
The term mart, as at present used in cement manufacture, is ap- 
plied to a loosely cemented mass of lime carbonate formexl in 
lake basins as described on a later page. Calcareous tufa and 
travertine are more or less compact limestones deposited by 
spring or stream waters along their courses. Oolitic limestones, 
so calK-d because of their their resemblance to a mass of fish- 
roe, are made up of small rounded grains of lime carbonate. 
Chalk is a fine-grained limestone composed of finely comminuted 
shells, particularly those of the foraminifera. The presence of 
much silica gives rise to a siliceous or cherty limestone. If the 



18 

silica present is in combination with alumina, the resulting lime- 
stone will be clayey or argillaceous. 

Chemical composition of limestone A theoretically pure lime- 
stone is merely a massive form of the mineral calcite. Such an 
ideal limestone would therefore consist entirely of calcium car- 
bonate or carbonate of lime, with the formula CaCO3 (CaO-f- 
CO2), corresponding" to the: composition calcium oxide (CaO) 
56 per cent. ; carbon dioxide or carbonic acid (CC)2) 44 per cent. 

As might be expected, the limestones we have to deal with in 
practice depart more or less widely from this theoretical com- 
position. These departures from ideal purity may taike place 
along either of two lines, 

a. The presence of magnesia in place of part of the lime ; 

b. The presence of silica, iron, alumina^ alkalies, or other im- 
purities. 

It seems advisable to discriminate between these two cases, 
even though a, given sample of limestone may fall under both 
heads, and they will therefore be discussed .separately. 

a. The presence of magnesia- in place of part of the lime. 
The theoretically pure limestones are, as above noted, composed 
entirely of calcium carbonate and correspond to the chemical 
formula CaCO3. Setting aside for the moment the question of 
the presence or absence of such impurities as iron, alumina, si- 
lica, etc., it may be said that lime is rarely the only base in a 
limestone. During or after the formation of the limestone a cer- 
tain percentage of magnesia is usually introduced in place of 
part of the lime, htus giving a more or less magnesian limestone. 
In the magnesian. limestones part of this calcium carbonate is 
replaced by magnesium carbonate (Mg CO;}), the general 
formula for a magnesian limestone being therefore 

x Ca COs+y Mg 03. 

In this formula x may vary from 100% to zero, while y will 
vary inversely from zero to 100%. In the particular case of this 
replacement where the two carbonates are united in equal 
molecular proportions, the resultant rock is called dolomite. It 
has the formula, CaCO3, MgCO3 corresponding to the com- 
position calcium carbonate 54.35 per cent. ; magnesium carbonate 
45.65 per cent. In the case where the calcium carbonate has 
been entirely replaced by magnesium carbonate, the resulting 



19 

pure carbonate of magnesia is called magnesite, having the 
formula MgCO^ and the composition magnesia (MgO) 47.6 
per cent.; carbon dioxide (CO2), 52.4 per cent. 

Rocks of this series may therefore vary in composition from 
pure calcite-limestones at one end of the series to pure magnesite 
at the other. The term limestone has, however, been restricted 
in general use to that part of the series lying in composition be- 
tween calcite and dolomite, while all those more uncommon 
phases carrying more magnesium carbonate than the 45.65 per 
cent, of dolomite are usually described simply as impure magne- 
sites. 

The presence of much magnesia in the finished cement is con- 
sidered undesirable, 3V> per cent, being the maximum permissi- 
ble under most specifications, and therefore the limestone to be 
used in Portland cement manufacture should carry not over 5 
to 6 per cent. o>f magnesium carbonate. 

Though magnesia is often described as an "impurity" in lime- 
stone, this word, as can be seen from the preceding statements, 
hardly expresses the facts in the case. The magnesium carbon- 
ate present, whatever its amount, simply serves to replace an 
equivalent amount of calcium carbonate, and the resulting rock, 
whether little or much magnesia is present, is still a pure carbon- 
ate rock. With the impurities to be discussed in later para- 
graphs, however, this is not the case. Silica, alumina, iron, 
sulphur, alkalies, etc., when presenit, are actual impurities, not 
merely chemical replacements of part of the calcium carbonate. 

b. The presence of silica, iron, alumina, alkalies, and other im- 
purities.- \Yhether a limestone consists of pure calcium carbon- 
ate or more or less of magnesium carbonate, it may also contain 
a greater or lesser amount of distinct impurities. From the 
point of view of the cement manufacturer, the more import an 
of these impurities are silica, alumina, iron, alkalies, and sul- 
phur, all of which have a marked effect on the value of the lime- 
stone as a cement material. These impurities will therefore be 
taken up in the order in which they are named above. 

The silica in a limestone may cccur either in combination with 
alumina, as a clayey impurity, or not combined with alumina. 
As the effect on the value of the limestone would be very di Cer- 
ent in the two cases, they will be taken up separately. 

Silica alone. Silica, when present in a limestone containing 
no alumina, mav occur in one of three forms, and the form in 



20 

which it occurs is of great importance in connection with cernert 
manufacture. 

(1) In perhaps its commonest form, silica is present in 
nodules, masses or beds of flint or chert. Silica occurring in 
this form will not readily enter into combination with the lime of 
a cement mixture, and a chert y or flinty limestone is therefore 
almost useless in cement manufacture. 

(2) In a few cases, as in the hydraulic limestone of Teil, 
France, a large amount of silica is present and very little 
alumina; notwithstanding which the silica readilv combines with 
the lime on burning. It is probable that in such cases the silica 
is present in the limestone in a verv finely divided condition, or 
possibly as hydrated silica, possibly as the result of chemical 
precipitation or of organic action. In the majority of cases, 
however, a highly siliceous limestone will not make a cement on 
burning unless it contains alumina in addition to the silica. 

(3) In the crystalline limestone (marbles) and less commonly 
in uncrystalline limestones, whatever silica is present may occur 
as a complex silicate in the form cxf shreds of mica, hornblende, 
or other silicate mineral. In this form silicate is somewhat in- 
tractable in the kiln, and mica and other silicate minerals are 
therefore to be; regarded as inert and useless impurities in- a ce- 
ment rock. These silicates will fitix at a lower temperature than 
pure silica and are thus not so troublesome as flint or chert. 
They are, however, much less serviceable than if the same 
amount of silica were present in combination with alumina as* a 
clay. 

Silica with alumina, Silica and alumina, combined in the 
form of clay, are common impurities in limestone, and are of 
special interest to the cement manufacturer. The best known 
example of such an argillaceous limestone is the cement rock of 
the Lehigh district of Pennsylvania. Silica and alumina, when 
present in this combined form, combine readily with the lime 
under the action of heat, and an argillaceous limestone therefore 
forms an excellent basis for a Portland cement mixture. 

Iron. Iron when present in a limestone occurs commonly as 
the oxide (Fe2C>3), or sulphide (FeS2) ; more rarely as iron 
carbonate or in a complex silicate. Iron in the oxide, carbonate 
or silicate form, is a useful flux, aiding in the combination of the 



21 

lime and silica in the kiln. When present as a sulphide, in the 
form of the mineral pyrite it is to be avoided in quantities over 2 
or 3 per cent. 

Physical characters of limestones. in texture, hardness, and 
compactness, the limestones vary from the loosely consolidated 
marls through the chalks to the hard compact limestones and 
marbles. Parallel with these variations are variations in absorp- 
tive properties and density. The chalky limestones may run as 
low in specific gravity as 1.85, corresponding to a weight of say 
110 pounds per cubif oot, while the compact limestones com- 
monly used for building purposes range in specific gravity be- 
tween 2.3 and 2.9, corresponding approximately to a range in 
weight of from 140 to 185 pounds per cubic foot. 

From the point of view of the Portland cement manufacturer, 
these variations in physical properties are of economic interest 
chiefly in their bearing upon two points : the percentage of water 
carried by the limestone as quarried, and the ease with which the 
rock may be crushed and pulverized. To some extent the two 
properties x counterbalance each other; the softer the limestone 
the more absorbent is it likely to be. These purely economic fea- 
tures \vill be discussed in more detail in later chapters. 

Effect of heating on limestone. On heating a non-magnesian 
limestone to or above 300 C., its carbon dioxide will be driven 
off, leaving quicklime (calcium oxide, CaO). If a magnesian 
limestone be similarly treated, the product would be a mixture of 
calcium oxide and magnesium oxide (MgO). The rapidity and 
perfection of this decomposition can be increased by passing 
steam or air through th,e burning mass. In practice this is ac- 
complished either by the direct injection of air or steam, or more 
simply by thoroughly wetting the limestone before putting it 
into the kiln. 

If, however, the limestone contains an appreciable amount of 
silica, alumina and iron, the effects of heat will not be of so sim- 
ple a character. At temperature of 800 C. and upwards these 
clayey impurities will combine with the lime oxide, giving sili- 
cates, aluminates and related salts of lime. In this manner a 
natural cement will be produced. An artificial mixture of cer- 
tain and uniform composition, burned at a higher temperature, 
will give a Portland cement, the details of whose manufacture 
are discussed on later pages. 



CHAPTER 4. 

RAW MATERIALS IN DETAIL. 

Argillaceous Limestone : Cement Rock. 

An argillaceous limestone containing approximately 75 per 
cent, of lime carbonate and 20 per cent, of clayey materials 
(silica, alumina, and iron oxide), would, of course, be the ideal 
material for use in the manufacture of Portland cement, as such 
rock would contain within itself in the proper proportions all 
the ingredients necessary for the manufacture of a good Port- 
land. It would require the addition of no other material, but 
when burnt alone would give a good cement. This ideal cement 
material is, of course, never realized in practice, but certain de- 
posits of argillaceous limestone approach the ideal composition 
very closely. 

The most important of these argillaceous limestone or "ce-- 
ment rock" deposits is, at present, that which is so extensively 
utilized in Portland cement manufacture in the "Lehigh district" 
of Pennsylvania and New Jersey. As this area still furnishes 
about two^thirds of all the Portland cement manufactured in the 
United States, its raw materials will be described in some detail 

Cement rock of the Lehigh district. The Lehigh district of 
thie cement trade comprises parts of P>erks, Lehigh, and North- 
ampton counties, Pennsylvania, and of Warren county, N' v '" 
Jersey. Within this relatively small area about twenty Port- 
land cement mills are located, producing slightly over two-thirds 
of the entire American output. As deposits of the cement rock 
used by these plants extend far beyond the present "Lehigh dis- 
trict," a marked extension of the district will probably take place 
as the needs for larger supplies of raw material becomes more 
apparent. 

The '"'cement rock" of the Lehigh district is a highly argil- 
laceous limestone of Trenton (Lower Silurian) age. The for- 
mation is about 300 feet in thickness in this area. The rock is 
a very dark gray in color and usually has a slaty fracture. In 
composition it ranges from about 60 per cent, lime carbonate 



23 

with 30 per cent, of clayey material, up to say 80 per cent, lime 
carbonate with 15 per cent, of silica, alumina and iron. The 
lower beds of the formation are always higher in lime carbonate 
than are the beds nearer the top of the formation. The content 
of magnesium carbonate in these cement rocks is always high, 
(as Portland cement materials go), ranging from 3 to 6 per cent. 

Xear, and in some cases immediately underlying these cement 
beds, are beds of purer limestone ranging from 85 to 96 per cent, 
lime carbonate. The usual practice in the Pennsylvania and 
Xe\v Jersey plants has been therefore to mix a relatively small 
amount of thiis purer limestone with the low lime "cement rock" 
in such proportions as to give a cement mixture of proper com- 
position. 

The economic and technologic advantages of using such a 
combination of materials are very evident. Both the pure lime- 
stone and the cement rock, particularly the latter, can be quarried 
very easily and cheaply. As quarried they carry but little water 
so that the expense of dryidg them is slight. The fact that about 
four-fifths of the cement mixture will be made up of a natural 
cement rock permits coarser granding of the raw mixture than 
would be permissible in plants using pure limestone or marl with 
clay. This point is more fully explained on a later page. 
It seems probable, also, that when using a natural cement 
rock as part of the mixture the amount of fuel necessary to clin- 
ker the mixture is less than when pure limestone is mixed with 
clay. 

Such mixtures of argillaceous limestone or "cement rock" 
with a small amount of pure limestone evidently possess import- 
ant advantages over mixtures of pure hard limestone or marl 
with clay. They are, on the other hand, less advantageous as 
cement materials than the chalky limestones discussed on 
later pages. 

The analyses in Table 2 are fairly representative of the ma- 
terials employed in the Lehigh district. The first four analyses 
are of "cement rock"; the last two are of the purer lim>estone 
used for mixing with it. 



24 



Analyses of Lchig/i district eminent materials. 





Cement rock 


Limestone 


Silica (Si02) 
Alumina (A1203) ) 


10.02 9.52 14.52 16.10 
6.26 4.72 6.52 2.20 


3.02 1.98 
1.90 0.70 


Iron Oxide (Fe2O3) ...( 
Lime carbonate (CaCO3) . . 
Magnesium carbon- 
ate (MgCOS) 


78.65 80.71 73.52 76.23 
4 71 4 92 4 69 3 54 


92 .05 95 . 15 
3 04 2.03 









"Cement rock" in other parts of the United States. Certain 
Portland cement plants, particularly in the western United 
States, are using combinations of materials closely similar to 
those in the Lehigli district. Analyses of the materials used at 
several of these plants are given in Table III. 

Analyses of "cement rock" materials from the western United 

States. 





Utah. 


California 


Colorado 


. 


Cement rock 


Limestone 


Cement rock 


Limestone 


Cement rock 


Limestone 


Silica (SiO2) 


21.2 6 

I- }. 

62.08 89 
3.8 


.8 


8 
.76 


20.06 
10.07 
3.39 
63.40 

1.54 


7.12 
2.36 
1.16 

87.70 

0.84 


14.20 
5.21 
1.73 
75.10 

1.10 


88.0 


Alumina (A12O3) 


Iron Oxide (Fe2O3) 


Lime carbonate (CaCO3)... 
Magnesium carbonate 
(MgCO3) 





In addition to the "cement rocks 7 ' noted in this chapter, it is 
necessary to call attention to the fact that many of the chalky 
limestones discussed 1 on page 26 are sufficiently argillace- 



25 

ous to be classed as 'cement rocks.'' I Because of their softness, 
however, all the chalky limestones will be described together. 

Pure hard limestones. 

Soon after the American Portland cement industry had be- 
come fairly well established in the Lehigh district, attempts 
were made in Xe\v York State to manufacture Portland cement 
from a mixture of pure limestone and clay. These attempts 
were not commercially successful, and although their lack of 
success was not due to any defects in the limestone used, a cer- 
tain prejudice arose against tine use of the hard limestones. In 
recent years, however, this has disappeared, and a very large 
proportion of the America:, output is now made from mixtures 
of limestone with clay or shale. (See page 21 for comparative 
figures.) This reestablishment in favor of the hard limestones 
is doubtless due, in great part, to recent improvements in grind- 
ing machinery, for .the purer limestones are usually much harder 
than argillaceous limestones like the Lehigh district "cement 
rock," and it was very difficult to pulverize them finely and 
cheaply with the crushing appliances in use when the Portland 
cement industry was first started in America. 

A series of analyses of representative pure hard limestones, 
together with analyses of the clays or shales with which they are 
mixed, is given in the table. 

Analyses of pure hard limestones and clayey materials. 

Limestones. 

Silica (Si02) 1.72 0.86 0.56 0.40 

Alumina (A12O2) 1.63 0.'63 1.23) 0.44 

Iron oxide (Fe2O3) 6.59 1.03 0.29f 

Lime carbonate (CaCO3) 90.58 97.06 97.23 97.99 

Magnesium carbonate (MgCOS) 0.75 0.42 

Clays and Shales. 

Silica (SiO2) 63.56 55.80 56.30 60.00 

Alumina (A12O2) | T23.36 

Iron oxide (Fe2O3) | 27.32 30.20 29.86] 4.32 

Lime carbonate (CaCOS) 3.60 2.54 " 1.70 

Magnesium carbonate (MgCO3) 2.60 1.50 



26 

The first limestone analysis given in the above table repre- 
sents a curious type, used in several plants in the Middle West. 
As will be noted, it is a relatively impure limestone, but its 
principal impurity is iron oxide. It contains 8.22 per cent, 
of iron oxide and alumina, as compared with 1.72 per cent, of 
silica : and therefore demands great care in the selection of a 
suitable high-silica clay to mix with it. 

Soft Limestones'. Chalk. 

Origin and general character. Chalk, properly speaking, is 
a pure carbonate of lime composed of the remains of the shells 
of minute organisms, among which those of foraminifere are 
especially prominent. The chalks and soft limestones discussed 
in this chapter agree, not only in having usually originated in 
this way, but also in being rather soft and therefore readily 
and cheaply crushed and pulverized. As Portland cement ma- 
terials they are, therefore, almost ideal. One defect, however, 
which to a small extent counterbalances their obvious advan- 
tages is the fact that most oif these soft, chalky limestones ab- 
sorb water quite readily. A chalky limestone which in a dry 
season will not carry over 2 per cent, of moisture as quarried, 
may, in consequence of prolonged wet weather show as high 
as 15 or 20 per cent, of water. This difficulty can, of course, be 
avoided if care be taken in quarrying to avoid unnecessary ex- 
posure to water and, if necessary, to provide facilities for stor- 
ing a supply of the raw materials during wet seasons. 

Geographic and geologic distribution in the United States. 
The chalks and chalky limestones are confined almost entirely 
to certain southern and western States. They are all of ap- 
proximately the same geologic ages, Cretaiceous or Tertiary, 
and are mostly confined to one division of the Cretaceous. 
The principal chalk or soft limestone deposits available for use 
in Portland cement manufacture occur in threei widely separated 
areas, occupying respectively (a) parts of Alabama and! Mis- 
sissippi ; (b) parts of Texas and Arkansas; and, (c) parts of 
Iowa, Nebraska, North and South Dakota. 



27 



Composition. In composition these chalks, or "rotten lime- 
stones," vary from a rather pure calcium carbonate, low in 
both magnesia and clayey materials, to an impure clayey lime- 
stone, requiring little additional clay to make it fit for use in 
[V.riland cement manufacture'. Analyses quoted from various 
authors of a number of these chalky limestones are given in 
Table IV, and will serve to show their range of composition. 

Analyses of Chalky Limestones. 





1 


c? 




of 








of 


'5 













^ 


o 




^H 


* r^H 


4^ 




a, 


C o3 


1 


O 


g 


cC 

c Q 




c -^ 


0) 


5 r 


-(-. ^ 


|B 


^ 




o> "*< 


C fcH 


75 ^ 


2 <j 


d ^ 


" ^ 




P 


ro 


Q 


^ 


>H 


S 


Silica 


12.13 


5.77 


23.55 


7.97 


8.20 


9.15 


Alumina 


4.17 










J 4.80 


Iron oxide 


3.28 


2.12 


1.50 


1.09 


7.07 


) 2.30 


Lime carbonate . . 


75.07 


90.15 


70.21 


88.64 


83.59 


63.75 


Magnesium carb'te 


.92 


.15 


.58 


.73 


n.d. 


1.25 



Fresh-Water Marls. 

Marls, in the sense in whidh the term is used in the Portland 
cement industry, are incoherent limestones which have been 
deposited in the basins of existing or extinct lakes. So far as 
chemical composition is concerned, marls are practically pure 
limestones, being composed entirely of calcium carbonate. 
Physically, however, they differ greatly from the compact 
rocks which are commonly described as limestones, for the 
marls are granular, incoherent deposits. This curious physical 
character of marls is due to the conditions under wlhich they 
have been deposited, and varies somewhat according to the par- 
ticular .conditions which governed their deposition in different 
localities. 

A warning to the reader concerning other uses of the term 
"marl" may profitably be introduced here. The meaning above 
given is that in which the term marl is commonly used in the 
cement industry at the present day. But in geological and agri- 
cultural reports, particularly in those issued before the Port- 



28 

land 1 cement industry became prominent in this country, the 
term marl has been used to cover several very different sub- 
stances. The following three uses of the term will be found 
particularly common, and must be guarded against when such 
reports are being examined in search for descriptions of de- 
posits of oement materials. 

(i.) In early days the term "'marls" and " marly tes" were 
used to describe deposits of calcareous shales and often cov- 
ered shales wihich were not particularly calcareous. This use 
of the term will be found in many of the earlier .geological re- 
ports issued by New York, Ohio, and other interior States. 

(2.) In New Jersey andi the States southward bordering 
on the Atlantic and Gulf of Mexico, the term marl is commonly 
applied to deposits of soft chailky or unconsolidated limestone, 
often containing considerable clayey and phosphatic matter. 
These limestones are of marine origin, and not related to the 
fresh-water marl deposits which are the subject of the present 
chapter. 

(3.) In the same States as are included in the last para- 
graph, but particularly in New Jersey and Virginia, large de- 
posits of the so-called 'green sand marls" occur. This mater- 
ial is, in no way, related! to the true marls (which are essential- 
ly lime carbonates), but consists almost entirely of an iron 
silicate,, with very small percentages of clayey, calcareous, and 
phosphatic matter. 

Origin or marls. The exact cause of the deposition of marls 
has been the subject of much investigation and discussion, par- 
ticularly in the past few years, since they have become of econ- 
omic importance. The reader who wishes to obtain further de- 
tails concerning this question will do well to refer to the fol- 
lowing series of papers. 

(i.) Blatchley, W. S., and Ashley, G. H. The Lakes of 
Northern Indiana, and their associated marl deposits, in 25th 
Ann. Kept. Indiana Dept. Geology and Natural Resources, pp. 

31-321. 

(2.) Davis, C. A. A contribution to the natural history of 
marl. Journal of Geology, Vol. 8, pp. 485-497. 

(3.) Davis, C. A. Second contribution to the natural his- 
tory of marl. Journal of Geology, Vol. 9, pp. 491-506. 

(4.) Davis, C. A. A contribution to the natural history of 
marl. Vol. 8, pt. 3, Reports Michigan Geological Survey, pp. 
65-102. 



29 

(5-) Lane, A. C. Notes on the origin of Michigan bog 
limes. Vol. X, pt. 3, Reports Michigan Geological Survey, pp. 
199-223. 

Disregarding tlu- points in controversy, which are of no par- 
ticular practical importance, it may be said that marls are de- 
posited in hikes by spring or stream waters carrying lime car- 
bonate in solution. The actual deposition is in part due to 
purely physical and chemical causes, and in part to the direct 
or indirect action of animal or vegetable life. The result, in 
any case, is that a calcareous deposit forms along the sides and 
over the bottom of the lake, this deposit consisting of lime car- 
bonate, mostly in a finely granular form, interspersed with shells 
and shell fragments. 

Geographic distribution of marl deposits. The geographic 
distribution of marl deposits is intimately related to the geo- 
logic history of the region in which they occur. MairNbeds are, 
as indicated in the preceding section, the result of the filling of 
lake basins. Lakes are: not common except in those portions 
of the United States which were affected by glacial action, since 
lakes are in general due to the damming of streams by glacial 
material. Workable marl deposits, therefore, are almost ex- 
clusively confined to those portions of the United States and 
Canada lying north of the former southern limit of the glaciers. 

Marl beds are found in the New England States, where they 
are seldom of important size, and in New York, where 
large beds occur in the central and western portions of the 
State. Deposits are frequent and important in Michigan, and 
in the northern portions of Ohio, Indiana, and Illinois. Marl 
beds occur in Wisconsin and Minnesota, but have not been as 
yet exploited for cement manufacture. 

Composition. As show : n by the analyses below, marls are 
usually very pure lime carbonates. They, therefore, require the 
addition of considerable clay to bring them up to the proper 
composition for at Portland cement mixture. 

The marls are readily excavated, but necessarily carry a large 
percentage of water. The mixture, on this account, is com- 
monly made in the wet way, which necessitates driving off a 
high percentage of water in the kilns. Analyses of typical marls 
and clays are given in the following table. 



Analyses of marls and clays used iu ccuicnt plants. 







Marl. 






Clay. 




Silica 


25 


3 


1 60 


40 48 


52 


63 75 


Alumina 










f 17 


16 40 


Iron oxide 
Lime carbonate . . . 
Magnesium carb'te 


| .10 
94.39 

.38 


93.0 
1.5 


1.55 

88.9 
.94 


20.95 
25.80 
.99 


) 5.0 
20.0 


6.35 
4.0 
2.1 



Alkali Waste. 



A very large amount of waste material results from the pro- 
cess used at alkali works in the manufacture of caustic soda. 
Tihis waste material is largely a precipitated form of calcium 
carbonate, and if it is sufficiently free from impurities, it fur- 
nishes a cheap source of lime for use in Portland cement manu- 
facture. 

The availability of alkali waste for this purpose depends 
largely on what process was used at the alkali plant. Leblanc 
process waste, for example, carries a very large percentage of 
sulphidies, which prevents its use as a Portland cement material. 
Waste resulting from the use of the ammonia process, on the 
other hand, is usually a very pure mass of lime, mostly in the 
formi of carbonate, though a little lime hydrate is commonly 
also present. As pyrite is not used in the ammonia process, its 
waste is usually low enough in sulphur to be used as a cement 
material. The waste may carry a low or a very high percent- 
age of magnesia, according to the character of the limestone 
that has been used. When a low-magnesia limestone has been 
used, the resulting was te is a very satisfactory Portland' ce- 
ment material. 

The following analyses are fairly representative of the waste 
obtained at alkali plants using the ammonia process. 



31 



inalyses of alkali waste. 





1 


2 


3 


4 


Silica (SiO2) 


60 


1 75 


1 98 


98 


Alumina (A12O3) 


) 


) 0.61 


C 1.41 


) 1.62 


Iron oxide (Fe2O3) 


( 3 04 


(. 

f 


) 
\ 1 38 


(. 
( 


Lime (CaO) 


) " v 
53.33 


) 
50.60 


48 29 


) 
50 44 


Magnesia ( MgO ) 


0.48 


5.35 


1.51 


4.97 


Alkalies (Na2O. K20) 


0.20 


64 


64 


50 


Sulphur trioxide (Co3) 
Sulphur (S) 


n.d. 
n d 


n.d. 

10 


1.26 
n d 


n.d. 
06 


Carbon dioxide (CO2) 


42.43 


^ 


39 60 


n.d 


Water and organic matter 


n d 


( 41 70 


3 80 


n d 













Of the analyses quoted in the preceding table, those in the 
first and third columns represent materials which are actually 
used in Portland cement manufacture in England and the 
United States. The alkali wastes whose analyses are given in 
the second and fourth columns are notably too high in mag- 
nesia to be advisable for such use. 

Blast furnace slag. 

True Portland cements, which must be sharply distinguished 
from the slag (or puzzolan) cements can be made from mix- 
tures which contain blast furnace slag as one ingredient. In 
this case the slag is intimately mixed with limestone and the 
mixture is finely powdered. It is then burned in kilns and the 
resulting clinker pulverized. 

The slags from iron furnaces consist essentially of lime 
(CaO), silica (Si()2), and alumina (A\2O^) ; though small 
percentages of iron oxide (FeO), magnesia (MgO), and sul- 
phur (S), are commonly present. Slag may therefore be re- 
garded as a very impure limestone or a very calcareous clay, 

The slag used at a German Portland cement plant has the 
following range in composition. 



32- 



Analysis of slag used in Portland cement 'manufacture 

Silicia (SiO2) 30. 35. 

Alumina (A1203) 10. 14. 

Iron oxide (FeO) 0.2 1.2 

Lime (CaO) ; 46. 49. 

Magnesia (MgO) 0.5 3.5 

Sulphur trioxide (SOS) . 0.2 0.6 



Clays and Shales. 

Clays are ultimately derived from, the decay of older rocks, 
the finer particles resulting from this decay being carried off and 
deposited by streams along their channels, in lakes, or along 
parts L- r the sea coast or sea bottom as beds of clay. In, chemi- 
cal composition the clays are composed essentially of silica and 
alnmina, though iron oxide is almost invariably present in more 
or less amount, while lime, magnesia, alkalies and sulphur are 
of frequent occurrence, though usually only in small percent- 
ages. 

Shales are clays which have become hardened by pressure. 
The so-called "fire-clays" of the Coal Measures arc shales, as 
are many of the other "clays" of commerce. 

For use as Portland cement materials clays or shales should 
be as free as possible from gravel and sand, as the silica present 
as pebbles or grit is practically inert in the kiln unless ground 
more finely than is economically practicable. In composition 
they should not carry less than 55 per cent, of silica, and pre- 
ferably from 60 to 70 per cent. The alumina and iron oxide to- 
gether should not amount to more than one-half the percent- 
age of silica, and the composition will usually be better the 
nearer the ratio Al2O3+Fe2O3=SiO2 is approached. 

~T~ 

Nodules of lime carbonate, gypsum or pyrite, if present in 
any quantity, are undesirable; though the lime carbonate is not 
absolutely injurious. Magnesia and alkalis should be low, 
preferably not above 3 per cent. 

Analyses of clays and shales'used in various American Port- 
land cement plants will be found on pages 27 and 30. 



33 



Slate. 

Slate is, so far as origin is concerned, merely a form of 
shale in which a fine, even and parallel cleavage has been de- 
veloped by pressure. In composition, therefore, it will vary 
exactly as do the shales considered on previous pages, and so 
far as composition alone is concerned, slate would not be worthy 
of more attention, as a Portland cement material, than any 
other shale. 

Commercial considerations in connection with the slate in- 
dustry, however, make slate a very important possible source of 
cement material. Good roofing slate is a relatively scarce mater- 
ial, and commands a good price when found. In the prepara- 
tion of roofing slate for the market so much material is lost 
during sawing, splitting, etc., that only about 10 to 25 per cent, 
of the amount quarried is salable as slate. The remaining 75 
to 90 per cent, is of no service to the slate miner. It is sent to 
the dump heap, and is a continual source of trouble and expense. 
This very material, however, as can be seen from the analyses 
quoted below, is often admirable for use, in connection with 
limestone, in a Portland cement mixture. As it is a waste pro- 
duct, it could be obtained very cheaply by the cement manufac- 
turer. 

Composition of American roofing slates. 





Max. 


Average 


Min. 


Silica (SiO2) 


68 62 


60.64 


54.05 


Alumina (A12O3) 


24.71 i 


18.05 


9.77 


Iron oxides (FeO Fe2O3) 


10 66 


6.87 


2.18 


Lime (CaO) 


5.23 


1.54 




Magnesia (MgO) 


6.43 . 


2.60 


0.12 


Alkalies (K2O Na2O) 


8.68 


4.74 


1.93 


Ferrous sulphide (FeS2) 


, 


0.38 




Carbon dioxide ^O2) 




1.47 




"Water of combination 




3 51 




Moisture below 110C 




0.62 













CHAPTER 5. 

ECONOMIC CONSIDERATIONS AND METHODS OF 
MANUFACTURE. 

Determining the possible value for Portland cement manu- 
facture of a. deposit of raw material is a complex problem, de- 
pending upon ai number of distinct factors, all of which must 
be given due consideration. The more important of these fac- 
tors are : 

(i.) Chemical composition od: the material. 

(2.) Physical character of the material. 

(3.) Amount oi material available. 

(4.) Location of the deposit with respect to transportation 
routes. 

(5.) Location of the deposit with respect to fuel supplies. 
(6.) Location of the deposit with respect to markets. 
The natural raw materials used at present in Portland cement 

manufacture are obtained by one of three methods, (a) quar- 
rying; (b) mining, and (c) dredging. When the cement 
manufacturer is given an opportunity to choose between these 
different methods of excavation, his choice will depend partly 
on the physical character of the material to be excavated and 
partly oin the topographical and geological conditions. Usually, 
however, there is no opportunity for a choice of methods, for 
in any given- case one of the methods will be so evidently the 
only possible mode of handling the material a,s to leave no room 
for other considerations. 

The three different methods of excavation will first be briefly 
considered, after which the cost of raw materials at the mill will 
be discussed. 

Quarrying. In the following pages the term "quarrying" 
will be used to cotver all methods of obtaining raw materials 
from open excavations, quarries, cuts or pits whether the 
material excavated be a limestone, a shale or a clay. Quarry- 
ing is the most natural and common method of excavating the 



35 

raw materials for cement manufacture. If marl, which is usu- 
ally worked by dredging, be excluded from consideration, it 
is probably within saife limits to say that 95 per cent, of the 
raw materials used at American Portland cement plants are 
obtained by quarrying. If marls be included, the percentages 
excavated by different method's would probably be about as 
follows : Quarrying, 88 per cent. ; dredging, 10 per cent. ; 
mining, 2 per cent. 

In the majority of limestone quarries the material is blasted 
out and loaded by hand on to cars or carts. In a few lime- 
stone quarries a. steam shovel is employed to do the loading, 
and in shale quarries this use of steam shovels is more fre- 
quent. In certain clay and shale pits, where the materials are 
of suitable character, the steam shovel does all the work, both 
excavating and loading the ra,w materials. 

The rock is usually shipped to the mill as quarried without 
any treatment except sledging it to convenient size for load- 
ing. At a few quarries, hbwever, a crushing plant is installed 
at the quarry, and the rock is sent as crushed stone to the mill. 
A few plants also havfe installed their driers at the quarry, and 
dry the stone before shipping it to the mill. Except the sav- 
ing of mill space thus attained, this practice seems to have little 
to commend it. 

Mining. The term "mining" will be used, in distinction 
from "quarrying," to cover methods of obtaining any kind of 
raw material by underground workings, through shafts or tun- 
nels. Mining is, of course, rarely employed in excavating ma- 
terials of sucht low value per ton as the raw materials for Port- 
land cement manufacture. Occasionally, however, when a thin 
bed of limestone or shale is being worked, its dip will carry it 
under such a thickness of other strata as to> make mining cheaper 
than stripping and quarrying, for that particular case. 

Mining is considerably more expensive work than quarrying, 
but there are a few advantages about it that serve to counter- 
balance the greater cost per ton of raw material. A mine can 
be worked steadily and economically in all kinds of weather, 
while an open cut or quarry is commonly in a mo>re or less un- 
workable condition for about three months of the year. Ma- 
terial won by mining is, moreover, always dry and clean. 

Dredging. The term "dredging" will be here, used to cover 
all methods of excavating soft, wet, raw materials. The fact 



36 

that the materials are wet implies that the deposit occurs in a 
basin or depression; and this in turn implies that the mill is 
probably located at a higher elevation than the deposit of raw 
material, thus necessitating up-hill transportation to the mill. 

The only raw material for Portland cement manufacture that 
is extensively worked by dredging, in the United States, is marl. 
Occasionally the clay used is obtained from deposits overlain 
by more or less water ; but this is rarely done except where the 
marl and clay are interbedded or associated in the same deposit. 

A marl deposit, in addition to containing much water diffused 
throughout its mass, is usually covered by a more or less consid- 
erable depth of water. This will frequently require the partial 
draining of the basin in order to get tracks laid near enough to 
be of service. 

In dredging marl the excavator is frequently mounted on a 
barge, which floats in a channel resulting from previous investi- 
gation. Occasionally, in deposits which either were originally 
covered by very little water or have been drained, the shovel is 
mounted on a car, running on tracks laid along the edge of the 
deposit. 

The material brought up by the diredge may be transported 
to the mill in two different ways, the choice depending largely 
upon the manufacturing processes in use at the plant, At 
plants using dome or chamber kilns, or where the marl is to 
be dried before sending to the kiln, the excavated marl is usu- 
ally loaded by the shovel on cars, and hauled to the mill by horse 
or steam power. At normal marl plants, using a very wet 
mixture, it is probable that the second method of transporta- 
tion is moire economical. This consists of dumping the marl 
from the excavator into tanks, adding sufficient water to make 
it flow readily, and) pumping the fluid mixture to the mill in 
pipes. 

Cost of raw materials at mill. The most natural way, per- 
haps, to express the cost of the raw material delivered at the 
mill would be to state it as being so many cents uper ton or 
cubic yard of raw material ; and this is the method followed by 
quarrymen or miners in general.. To the cement manufacturer, 
however, such an estimate is not so suitable as one based on the 
cost of raw materials per ton or barrel of finished cement. 

In the case of hard and comparatively dry limestones or shales, 
it mav be considered that the raw material loses 33 1-3 per cent. 



37 

in weight on burning. Converting this relation into pounds of 
raw material and of clinker we find that 600 pounds of dry 
raw material will make about 400 pounds of clinker. Allowing 
something for other losses in the process of manufacture, it is 
convenient and sufficiently accurate to estimate that 600 pounds 
of dry raw material will give one barrel of finished cement. 
These estimates must be increased if the raiw material carry any 
appreciable amount of water. Clays will frequently contain 15 
per cent, or more of water ; while soft chalky limestones, if 
quarried during wet weather, may carry as high as 15 to over 
20 per cent. A Portland cement mixture composed of a pure 
chalky limestone and a clay might, therefore, average 10 to 20 
per cent, of water ; and consequently about 700 pounds of such 
a mixture would be required to make one barrel of finished ce- 
ment. 

With marls the loss on drying and burning is much greater. 
Russell states* that according to determinations made by E. D. 
natural deposits, contains about 47 1-2 pounds of lime carbonate 
and 48 pounds of water. In making cement from a mixture of 
marl and clay, therefore, it would be necessary to figure on ex- 
cavating and transporting over 1,000 pounds of raw material 
for every barrel of finished cement. 

From the preceding notes it will be understood that the cost 
of raw materials at the mill, per barrel of cement, will vary 
not only with the cost of excavation, but with the kind of ma- 
terials in use. 

[IT dealing with hard dry materials, extracted from open 
quarries near the mills, the cost of raw materials may vary be- 
tween 8 cents and 15 cents per barrel of cement. The lower 
figure named is probably about the lowest attainable with good 
management and under favorable natural conditions ; the higher 
figure is probably a maximum for fairly careful management 
of a quarry under eastern labor conditions. Whem it is neces- 
sary to mine the materials, the cost will be somewhat increased. 
Cement rock has been mined at a cost equivalent to 10 cents 
per barrel of cement; but the figure is attained under particu- 
larly favorable conditions. The cost at mining and transpor- 
tation may reach from this figure up to 20 cents per barrel. 

*22nd Ann. Kept., U. S. Geol. Surv., pt. 3, p. 657. 



38 

METHODS OF MANUFACTURE. 

If, as in the present volume, we exclude from con- 
sideration the so-called "natural Portlands," Portland ce- 
ment may be regarded as being an artificial product, obtained 
by burning to semi-fusion an intimate mixture of pulverized 
materials, this mixture containing lime, silica and alumina, 
varying in proportion only with certain narrow limits ; and by 
crushing finely the clinker resulting from this burning. 

If this restricted definition of Portland cement be accepted, 
four points may be regarded as being of cardinal importance in 
its manufacture. These are : 

1 i ) The cement mixture must be of the proper chemical 
composition. 

(2) The materials of which it is composed must be carefully 
ground and intimately mixed before burning. 

(3) The mixture must be burned at the proper temperature. 

(4) After burning, the resulting clinker must be finely 
ground. 

The first named of these points the chemical composition 
of the mixture can be more advantageously discussed after 
the other th/ree points have been disposed of. The subjects 
will, therefore, be taken up in the following order : 

Preparation of the mixture for the kiln. 
Burning the mixture. 

Grinding the clinker, addition of gypsum, etc. 
Composition and properties of Portland cement. 

PREPARATION OF THE MIXTURE FOR THE KILN. 

The preparation of the mixture for the kiln involves the re- 
duction of both of the raw materials to a very fine powder, and 
their intimate mixture. In practice the raw materials are 
usually crushed more or less finely, and them mixed, after which 
the final reduction to powder takes place. Two general methods 
of treatment the dry and the wet are in use at different 
plants. Unless the limey constituent of the mixture is a marl, 
already full of water, the dry method is almost invariably fol- 
lowed. This consists merely in keeping the materials in as dry 



a condition as possible throughout the entire process of crush- 
ing" and mixing; and, if the raw materials originally contained 
a little moisture, they are dried before being powdered and 
mixed. In the wet method, on the other hand, the materials are 
powdered and mixed while in a very fluid state, containing 60 
per cent, or more of water. 

DRYING THE RAW MATERIALS. With the exception of the 
marls and clays used in the wet method of manufacture, Port- 
land cement materials are usually dried before the grinding is 
commenced. This is necessary because the raw materials, as 
they come from the 1 quarry, pit or mine, will almost invariably 
carry appreciable, though often very small, percentages of 
water, which greatly reduces the efficiency of most modern types 
of grinding mills, and tenclls to clog the discharge screens. 

PERCENTAGE OF WATER IN RAW MATERIALS. The percent- 
age of water thus carried by the crude raw material will depend 
largely on the character of the material ; partly on the method 
of handling and storing it ; and partly on weather conditions. 

Im the case of hard limestones, freshly quarried, the water 
will commonly range from 1-2 per cent, to 3 per cent., rarely 
reaching or exceeding the higher figure except in the very wet 
quarries or during a rainy season. Such limestones, compara- 
tively dry when quarried, are frequently sent to the grinding 
mills without artificial drying. 

With the soft, chalky limestones, which absorb water very 
rapidly, the percentage can usually be kept down to. 5 per cent, 
or less in dry weather; while prolonged wet weather may ne- 
cessitate the handling at the mill of material carrying as high 
as 15 to 20 per cent, of water. 

The clays present a much more complicated case. In addi- 
tion to the hydroscopic or mechanically-held water that they 
may contain, there is also always present a certain percentage 
of chemically combined water. The amount of hydroscopic 
water present will depnd on the treatment and exposure of the 
clay ; and may vary from I per cent, or so in clays which have 
been stored and air-dried to as high as 30 per cent, in fresh 
clays. The chemically combined water will depend largely on 
the composition of the clay, and may vary from 5 to 12 per 
cent. The hygroscopic or mechanically held water of clays can 
be driven off at a temperature of 212 F., while the chemically 



40 

combined water is lost only at a low red heat. The total water, 
therefore, to be driven off from clays may range from 6 to 42 
per cent., depending on the weather, the drainage of the clay 
pit, and the care taken in preventing unnecessary exposure to 
moisture of the excavated clay. The average total amount of 
moisture will probably be about 15 per cent. 

In dealing with shales, the mechanically-held water will rarely 
rise above 10 per cent., and can commonly be kept well below 
that limit. An additional 2 to 7 per cent, of water will be car- 
riedi, by any shale, in a state of chemical combination. 

At a few plants marl is used, with clay, in a dry process. As 
noted -elsewhere, the marls, as excavated, carry usually about 
50 per cent, of water. This case presents a more difficult prob- 
lem than do the other raw materials, because the vegetable mat- 
ter usually present in marls is eixtremely retentive of water. 

It will be seen, therefore, that cement materials may carry 
from i per cent, to 50 per cent, of water when they reach the 
mill. In a dry process it is necessary to remove practically all 
of this water before commencing the grinding of the .materials. 
One reason for this is that fine pulverizing can not be economic- 
ally or satisfactorily accomplisheid unless absolutely dry mate- 
rial is fed to the grinding machinery. 

Another reason, which is one of convenience rather than of 
necessity, is that the presence of water in the raw materials com- 
plicates the calculation of the cement mixture. 

Methods and cost of drying. The type of dryer commonly 
used in cement plants is a cylinder approximately 5 feet in di- 
ameter and 40 feet or so in length, set at a slight inclination to 
the horizontal, and rotating on bearings. The wet raw mater- 
ial is fed in at the upper end af the cylinder, and it moves 
gradually toward the; lower end, under the influence of gravity, 
as the cylinder revolves. In many dryers angle irons are bolted 
to the interior in such a way as to lift and drop the raw mater- 
ial alternately, thus exposing it more completely to the action 
of the heated gases, and materially assisting in the drying pro- 
cess. The dried raw material falls from the lower end of the 
cylinder into an elevator boot, and is then carried to the grind- 
ing mills. 

The drying cylinder is heated either by a separate furnace or 
by waste gases from the cement kiln. In either case the pro- 



41 

ducts of combustion are introduced) into the cylinder at its 
lower end, and drawn through it, and escape up a stack set at 
the upper end of the dryer. 

The dryer abovfe described is the simplest, and is most com- 
monly used. For handling the small percentages of water con- 
tained in most cement materials it is very efficient, but for deal- 
ing with high percentages of water, such as are encountered 
when marl is to be used in a dry process, it seems probable that 
dlouble-heating dryers will be found more economical. This 
type is exemplified by the Ruggles-Coles dryer, in 
which a double cylinder is employed. The wet raw 
material is fed into the space between the inner and outer 
cylinders, while the heated gases pass first through the inner 
cylinder, and then, in a reverse direction, through the space be- 
t \\een the inner and outer cylinders. This double-heating type 
of dlryer is employed in almost all of the slag cement plants in 
the United States, and is also in use in several Portland cement 
plants. 

When vertical kilns were in use, drying floors and drying 
tunnels were extensively used, but at present they can be found 
in only a few places, being everywhere else supplanted by the 
rotary dryers. 

The cost of drying will depend 011 the cost of fuel, the per- 
centage of water in the wet material and the type of dryer, 
iwen under the most unfavorable conditions five pounds of 
water can be expected to be evaporated per pound of coal used, 
while a good dryer will usually evaporate seven or eight pounds 
of water per pound of coal. 

GRINDING AND MIXING DRY METHODS. Part at least of 
the grinding is usually accomplished before the drying, but for 
convenience the subjects have been separated in the present 
paper. Usually the limestone: is sent through a crusher at the 
quarry or mill before being dried, and occasionally the raw ma- 
terial is further reduced in a Williams mill, etc., before drying, 
hut the principal part of the reduction always takes place after 
the material has been dried. 

After the two raw materials have been separately driedi they 
may be mixed immediately, or each may be further reduced sep- 
arately before mixing. Automatic mixers, of which many 
types are on the market, give a mixture in proportions deter- 
mined upon from analysis of the materials. 



42 

The further reduction of the mixture is usually carried on in 
two stages, the material being ground to say 30 mesh in a ball 
mill, komminuter, Griffin mill, etc., and finally reduced in a tube 
mill. At a few plants, however, single stage reduction is prac- 
ticed in Gnffn or Huntington mills, while at the Edison plant 
at Stewartsville, N. T., the reduction is accomplished in, a series 
of rolls. 

The majority of plants use either the Griffin mill and tube 
mill or the ball andi tube mills, and there is probably little differ- 
ence in the cost of operating these two combinations. The ball 
mill has never been quite as much of a success as its companion, 
the tube mill, and has been replaced at several plants by the 
komminuter. 

FINENESS OF MIXTURE. After its final reduction, and when 
ready for burning, the mixture will usually run from 90 to 95 
per cent, through a loo-mesh sieve. In the plants of the Lehigh 
district the mixture is rarely crushed as fine as when limestone 
and clay are used. Newberry* has pointed out in explanation 
for this that an argillaceous limestone (cement rock) mixed 
with a comparatively small quantity of purer limestone, as in 
the Lehigh plants, requires less thorough mixing and less fine 
grinding than when a mixture of limestone and clay (or marl 
and clay) is uesd, for even the coarser particles of the argil- 
laceous limestone will vary so little in chemical composition 
from the proper mixture as to affect the quality of the resulting 
cement but little, should either mixing or grinding be incom- 
pletely accomplished. 

A very good example of typical Lehigh Valley grinding of 
raw material is afforded by a specimen examined* by Prof. E. 
D. Campbell. This specimen of raw mix ready for burning was 
furnished by one of the best of the eastern Pennsylvania ce- 
ment plants. A mechanical analysis oif it showed the following 
results : 

Mesh of sieve. 

50 100 200 

Per cent, passing 96.9% 85.6% 72.4% 

Per cent, residue 3.1% 14.4% 27.6^ 

The material, therefore, is so coarsely ground that only a 
trifle over 85 per cent, passes a loo-mesh sieve. 

"Twentieth Ann. Kept. U. S. Geol. Surv., Pt. 6, p. 545. 
"Journal Amer. Chem. Soc., vol. 25. 



43 

GRINDING AND MIXING SLAG-LIMESTONE MIXTURES. 
While the manufacture of Portland cement from a mixture of 
slag and limestone is similar in general theory and practice to 
its manufacture from a limestone-clay mixture, certain inter- 
esting difference occur in the preparation of the mixture. In 
the following paragraphs the general methods of preparing 
mixtures of slag and limestone for use in Portland cement manu- 
facture will first be noted, after which certain processes pecu- 
liar to the use of this particular mixture will be described sep- 
arately. 

General methods. After it had been determined that the 
pozzuolanic cement made* by mixing slag with lime without 
subsequent burning of the 'mixture, was not an entirely satisfac- 
tory structural material, attention was scon, directed toward the 
problem of making a true Portland cement from such slag. The 
blast-furnace slags commonly available, while carrying enough 
silica and alumina for a cement mixture, are too low in lime. 
to be suitable for Portland cement. Additional lime must be 
added, usually in the form of limestone ; the slag and limestone 
must be well mixed and the mixture properly burned. The 
general methods for accomplishing the proper mixture of the 
materials vary in details. It seems probable that the first meth- 
od used in attempting to make a true Portland cement from 
slag, was to dump the proper proportion of limestone, broken 
into small lumps, into molten slag. The idea was that both 
mixing and calcination could thus be accomplished in one stage ; 
but in practice it was found that the resulting cement was vari- 
able in composition and always low in grade. This method has 
accordingly fallen into disuse, and at present three different 
general processes of preparing the mixture are practiced at dif- 
ferent European and American plants. 

1. The slag is granulated, dried, and ground, while the 
limestone is dried and ground separately. The two materials 
are then mixed in proper proportions, the mixture is finely pul- 
verized in tube mills, and the product is fed in a powdered state 
to rotary kilns. 

2. The slag is granulated, dried, and mixed with slightly 
less than the calculated proper amount of limestone, which has 
been previously dried and powdeired. To this mixture is added 

*See Municipal Engineering, vol. 24, p. 335, May, 1903. 



44 

sufficient powdered slaked lime (say 2 to 6 per cent.) to bring 
the mixture up to correct composition. The intimate mixture 
and final reduction are then accomplished in ball and tube 1 mills. 
About 8 per cent, of water is then added, and the slurry is made 
into bricks, which are dried and burned in a dome or chamber 
kiln. 

3. Slag is granulated and mixed, while still wet, with crushed 
limestone in proper proportions. This mixture is run through 
a rotary calciner, heated by waste kiln gases, in which the tem- 
perature is sufficient not only to dry the mixture, but also to 
partly po'wder it, and to reduce most of the limestone to quick- 
lime. The mixture is then pulverized and fed into rotary kilns. 

Of the three general processes above described, the second is 
unsuited to American conditions. The first and third are adapt- 
ed to the use of the rotary kiln. The third seems to be the 
most economical, and has given remarkably low fuel consump- 
tion in practice, but so far has not been taken up in the United 
States. 

Certain points oif manufacture peculiar to the use of mix- 
tures of slag and limestone will now be described. 

Composition of the slag. The slags available for use in Port- 
land cement manufacture are of quite common occurrence in 
iron-producing districts. Those best suited for such use are 
the more basic blast-furnace slags, and the higher such slags 
run in lime the more available they are for this use. The slags 
utilized will generally runi from 30 to 40 per cent. lime. The 
presence of over 3 peir cent, or so of magnesia in a slag is of 
course enough to render its use as a Portland cement material 
inadvisable ; and on this account slags from furnaces using do- 
lomite (magnesian limestone) as a flux, are unsuited for ce- 
ment manufacture. The presence of any notable percentage of 
sulphur is also a drawback, though, as will be later noted, part 
of the sulphur in the slag will be removed during the process 
of manufacture. 

Granulation of slag. If slag be allowed to cool slowly it 
solidifies into a dense, tough material, which is not readily re- 
duced to the requisite fineness for a cement mixture. If it be 
cooled suddenly, however, ais by bringing the stream of molten 
slag into contact with cold water, the slag is "granulated," i. e., 
it breaks up inito small porous particles. This granulated slag 
or "slag sand" is much more readily pulverized than a slowly 



45 

cooled slag ; its sudden cooling has also intensified the chemical 
activity of its constituents so as to give it hy'draulic properties, 
while part of the sulphur contained in the original slag has 
been removed. The sole disadvantage of the process of granu- 
lating slag is that the product contains 20 to 40 per cent, of 
water, which must be driven off before the granulated slag is 
sent to the .grinding machinery. 

In practice the granulation of the slaig is effected by directing 
the stream of molten slag direct from the furnace into a sheet- 
iron through. A small stream of water flows along this trough, 
the quantity and rate of flow of the water being regulated so as 
to give complete granulation of the slag without using an ex- 
cessive amount of water. The trough may be so directed as to 
discharge the granulated slag into tanks or into box cars, which 
are usually perforated at intervals along the sides so as to al- 
low part of the water to drain off. 

Drying the slag. As above noted, the granulated slag may 
carry from 20 to; 40 per cent, of water. This is removed by 
treating the slag in rotary dryers. In practice such driers give 
an evaporation of 8 to 10 pounds of water per pound of coal. 
The practice of slag drying is very fully described in Vol. 10 
of the Mineral Industry, pages 84-95, where figures and de- 
scriptions of various driers aire also given, with data on their 
evaporative efficiency. As noted earlier in this article, one of 
the methods of manufacturing Portland cement from slag puts 
off the drying of the slag until after it has been mixed with the 
limestone, and then accomplishes the drying by utilizing waste 
heat from the kilns. Kiln gases could of course be used anv- 
way in the slag driers, but it so happens that they have not been 
so used except in plants following the method in question. 

Grinding the slag. Slag can be crushed with considerable 
ease to about 50 mesh, but notwithstanding its apparent brittle- 
ness it is difficult to grind it finer. Until the introduction of the 
tube mill in fact it was almost impossible to reduce this material 
to the fineness necessairy for a cement mixture, and the proper 
grinding of the slag is still an expensive part of the proceiss, as 
compared with the grinding of limestone, shales, or clay. 

Composition of the limestone. As the slag carries all the si- 
lica and alumina necessary for the cement mixture, the lime- 
stone to be added to it should be simply a pure lime carbonate. 



46 

The limestone used for flux at the furnace which supplies the 
slag will usually be found to be of suitable composition for use 
in making up the cement mixture. 

Economics of using slag-limestone -mixtures. The manufac- 
ture of a true Portland cement from a mixture of slag and 1 lime- 
stone presents certain undoubted advantages over the use of any 
other raw materials, while it has also a few disadvantages. 

Probably the most prominent of the advantages lies in the 
fact that the most important raw material the slag can usu- 
ally be obtained more cheaply than an equal amount of natural 
raw material could be quarried or mined. The slag is a waste 
product, and a troublesome material to dispose of, for which 
reasons it is obtained at small expense to the cement plant. An- 
other advantage is due to the occurrence of the lime in the slag 
as oxide, and not as carbonate. The heat necessary to drivte 
off the carbon dioxide from an equivalent mass of limestone 
is therefore saved when slag farms part of the cement mixture, 
and very low fuel consumption is obtained when slag-limestone 
mixture is burned, 

Of the disadvantages, the toughness of the slag and the ne- 
cessity for drying it before grinding are probably the most im- 
portant. These serve to partly counterbalance the advantages 
noted above. A third difficulty, which is not always apparent at 
first, is that of securing a proper supply of suitable slag. Un- 
less the cement plant is closely connected in ownership with the 
furnaces from which its slag supply is to be obtained, this diffi- 
culty maiy become very serious. In a season when a good iron 
market exists the furnace manager will naturally give little 
thought to the question of supplying slag to an independent 
cement plant. 

The advantages of the mixture, however, seem to outweigh 
its disadvantages, for the manufacture of Portland cement from 
slag is now a large and growing industry in both Europe and 
America. Two Portland cement plants using slag and lime- 
stone as raw materials have been established for some time in 
this country, several others are in course of construction at pres- 
ent, and it seems probable that in the near future Alabama will 
join Illinois and Pennsylvania as am important producer of Port- 
land cement from slag. 



47 

GRINDING AND MIXING WET METHODS. Wet methods of 
preparing Portland cement mixtures date back to the time when 
millstones and similar crude grinding contrivances were in use. 
With such imperfect machinery it was almost impossible to 
grind dry materials fine enough to give a good Portland cement 
mixture. The advent of good grinding machinery has practi- 
cally driven out wet methods of manufacture in this country, 
except in dealing with materials such as marls, which naturally 
carry a large percentage of water. One or two plants in the 
United States do, it is true, deliberately add water to a lime- 
stone-clay mixture; but the effect of this practice on the cost 
sheets of these remarkable plants is not encouraging. 

In preparing cement mixtures from marl and clay, a few 
plants dry both materials beifore mixing. It seems probable 
that this practice will spread, for the wet method of mixture is 
inherently expensive. At present, however, almost all marl 
plants use wet methods of mixing, and it is therefore necessary 
to give some space to a discussion of such methods. 

Certain points regarding the location, physical condition, and 
chemical composition of the marls and clays used in such mix- 
tures have important effects upon the cost of the wet process. 
As regards location!, considered on a large scale, it must be 
borne in mind that marl deposits of workable size occur only 
in the Northern States and in Canada. In consequence the cli- 
mate is unfavorable to continuous working throughout the 
year, for the marl is usually covered with water, and in winter 
it is difficult to secure the material. In a minor sense location 
is still an important factor, for marl deposits necessarily and in- 
variably are found in depressions ; and the mill must, therefore, 
just as necessarily, be located at a higher level than its source 
of raw material, which involves increased expense in transport- 
ing the raw material to the mill. 

Glacial clays, which are usually employed in connection with 
marl, commonly carry a much larger proportion of sand and 
pebbles than do the sedimentary clays of more southern regions. 

The effect of the water carried by the marl has been noted on 
an earlier page. The material as excavated will consist approxi- 
mately of equal weights of lime carbonate and of water. This 
on the face of it would seem to be bad enough as a business pro- 
position ; but we find that in practice more water -is often added 
to permit the marl to be pumped up to the mill. 



48 

On the arrival of the raw materials at the mill the clay is 
often dried, in order to simplify the calculation of the mixture. 
The reduction of the clay is commonly accomplished in a dis- 
integrator or in edge-runner mills, after which the material is 
further reduced in a pug mill, sufficient water being here added 
to enable it to be pumped readily. It is then ready for mixture 
with the marl, which at some point in its course has been screen- 
ed to remove stones, wood, etc., so far as possible. The slurry 
is further ground in pug mills or wet grinding mills of the disk 
type ; while the final reduction takes place commonly in wet tube 
mills. The slurry, now containing 30 to 40 per cent, of solid 
matter and 70 to 60 per cent, of water, is pumped into storage 
tanks, where it is kept in constant agitation to avoid settling. 
Analyses of the slurry are taken at this point, and the mixture 
in the tanks is corrected if found to be of unsatisfactory com- 
position. After standardizing, the slurry is pumped into the 
rotary kilns. Owing to the large percentage of water contain- 
ed in the slurry the fuel consumption per barrel of finished ce- 
ment is 30 to 50 per cent, greater, and the output of each kiln 
correspondingly less than in the case of a dry mixture. 

It may be of interest, for comparison with the above descrip- 
tion, of the wet process with rotajry kilns, to insert a description 
of the semi-wet process as carried on a few years ago at the 
dome kiln plaint of the Empire Portland Cement Company at 
Warners, N. Y. The plant has been remodeled since that date, 
but the processes formerly followed are still of interest, as they 
resulted in a high-grade though expensive product. 

At the Empire plant the marl and clay were obtained from a 
swamp about three- fourths of a mile from the mill. A revolv- 
ing derrick with clam-shell bucket was employed for excaivat- 
ing the marl, while the clay was dug with shovels. The mater- 
ials were taken to the works over a private narrow-gauge road, 
on cars, carrying about three tons each, drawn by a small loco- 
motive. At the mill the cars were hauled up an inclined 1rack, 
by means of a cable and dlrum, to the mixing floor. 

The clay was dried in three Cummer "Salamander" driers, 
after which it was allowed to cool, and then carried to the mills. 
These mills were of the Sturtevant "rock emery" type, and re- 
duced the clay to a fine powder, in which condition it was fed, 
after being weighed, to the mixer. The marl was weighed and 
sent directly to the mixer, no preliminary treatment being neces- 



49 

sary. The average charge was about 25 per cent, clay and 
about 75 per cent. marl. 

The mixing was carried on in a mixing pan 12 feet in diame- 
ter, in which two large rolls, each about 5 feet in diameter, and 
1 6-inch face, ground and mixed the materials thoroughly. The 
mixture was then sampled and analyzed, after which it was 
carried by a belt conveyor to two pug mills, where the mixing 
was completed and the slurry formed into slabs about 3 feet 
long and 4 to 5 inches in width and height. These on issuing 
from the pug mill were cut into a number of sections, so as to 
give bricks about 6 inches by 4 inches by 4 inches in size. The 
bricks were then placed on slats, which were loaded on rack 
cars and run into the drying tunnels. The tunnels were heated 
by waste gases from the kilns and required from twenty- four 
to thirty-six hours to dry the bricks. 

After drying the bricks were fed into dome kilns, twenty of 
which were in use, being charged with alternate layers of coke 
and slurry bricks. The coke charge for a kiln was about four 
or five tons, and this produced 20 to 26 tons of clinker at each 
burning, thus giving a fuel consumption of about 20 per cent, 
as compared with the 40 per cent, or so required in the rotary 
kilns using wet materials. From thirty-six to forty hours were 
required for burning the charge. After coaling, the clinker was 
shoveled out, picked over by hand, and reduced in a Blake 
crusher, Smidth ball mills, and Davidsen tube mills. 

Composition of mixture. The cement mixture ready for 
burning will commonly contain from 74 to 77.5 per cent, of 
lime carbonate, or an equivalent proportion of lime oxide. Sev- 
eral analyses of actual cement mixtures are given in the follow- 
ing table. Analysis No. i, with its relatively high percent- 
age of magnesia, is fairly typical of Lehigh Valley practice. 
Analyses Nos. 2 and 3 show mixtures low in lime, while analy- 
sis No. 4 is probably the best proportioned of the four, especial- 
lv in regard to the ratio between silica and alumina plus iron. 
This ratio, for ordinary purposes, should be about 3.-, as the 
cement becomes quicker setting and lower in ultimate strength 
as the percentage of alumina increases. If the alumina percent- 
age be carried too high, moreover, the mixture will give a fusi- 
ble, sticky clinker when burned, causing trouble in the kilns. 



50 

Analyses of cement mixtures. 

1234 

Silica 12.62 13.46 13.85 11.77 

Alumina and iron oxide 6.00 ? 7.20 4.35 

Carbonate of lime 75.46 73.66 73.93 76.84 

Magnesia 2.65 ? ? 1.74 

BURNING THE MIXTURE. 

After the cement mixture has been carefully prepared, as de- 
scribed in preceding pages, it must be burned with equal care. 

In the early days of the Portland cement industry a simple 
vertical kiln, much like that used for burning lime and natural 
cement, was used for burning the Portland cement mixture. 
These kilns, while fairly efficient so far as fuel consumption 
was concerned, were expensive in labor, and their daily output 
was small. In France and Germany they were soon supplanted 
by improved types, but still stationary and vertical, which gave 
very much lower fuel consumption. In America, hcwever, 
where laibor is expensive while fuel is comparatively cheap, an 
entirely different style of kiln has been evolved. This is the ro- 
tary kiln. With the exception of a very few of the older plants, 
which have retained vertical kilns, all American Portland ce- 
ment plants are now equipped with rotary kilns. 

The history of the gradual evolution of the rotary kiln is of 
great interest, but as the subject can not be taken up here, ref- 
erence should be made to the papers cited below* in which de-- 
tails, accompanied often by illustrations of early types of rotary 
kilns are given. 

*Duryee, E., The first manufacture of Portland cement by the 
direct rotary kiln process. Engineering News, July 26, 1900. 

Lesley, R. W., History of the Portland cement industry in the 
United States. 8 vo. pp. 146, Philadelphia, 1900. 

Lewis, F. H., The American rotary kiln process for Portland ce- 
ment, in The Cement Industry, pp. 188-199, New York, 1900. 

Matthey, H., The invention of the new cement burning method. 
Engineering and Mining Journal, vol. 67, pp. 555, 705; 1899. 

Stanger, W. H., and Blount, B., The rotary process of cement 
manufacture. Proc. Institution Civil Engineers, vol. 145, pp. 44- 
136; 1901. 

Editorial, The influence of the rotary kiln on the development 
of Portland cement manufacture in America. Engineering News, 
May 3, 1900. 



51 

The design, construction and operation of the vertical sta- 
tionary kilns of various types is discussed in many reports in 
Portland cement, the most satisfactory single paper being prob- 
ably that referred to below*. As the subject is, in America, at 
least, a matter of simply historical interest, no description of 
these kilns or their operation will be given in the present bulle- 
tin. 

At present, practice in burning at the different American ce- 
ment plants is rapidly approaching uniformity, though differ- 
ences in materials, etc., will always prevent absolute uniformity 
from being reached. The kiln in which the material is burned 
is now almost invariably of the rotary type, the rotary process, 
which is essentially American in its development, being based 
upon the substitution of machines for hand labor wherever pos- 
sible. A brief summary of the process will first be given, after 
\N hich certain subjects of interest will be taken up in more de- 
tail. 

Summary of burning process. As at present used, the rotary 
kiln is a steel cylinder about 6 feet in diameter ; its length, for 
dry materials, is usually 60 or 80 feet, while for wet mixtures an 
8o-foot, or even longer, kiln is frequently employed. 

This cylinder is set in a slightly inclined position, the inclina- 
tion being approximately one-half inch to the foot. The kiln is 
lined, except near the upper end, with very resistant fire brick, 
to withstand both the high temperature to which its inner sur- 
face is subjected and also the destructive action of the molten 
clinker. 

The cement mixture is fed in at the upper end of the kiln, 
while fuel (which may be either powdered coal, oil, or gas), is 
injected at its lower end. The kiln, which rests upon geared 
bearings, is slowly revolved about its axis. This revolution, in 
connection with the inclination at which the cylinder is set, 
gradually carries the cement mixture to the lower end of the 
kiln. In the course of this journey the intense heat generated 
by the burning fuel first drives off the water and carbon dioxide 
from the mixture, and then causes the lime, silica, alumina, and 

*Stanger, W. H., and Blount, B., Gilbert, W., and Candlot, E., 
(Discussion of the value, design and results obtained from various 
types of fixed kilns). Proc. Institution Civil Engineers, vol. 145, pp. 
44, 48, 81, 82, 99, 100; 1901. 



52 

iron to combine chemically to form the partially fused mass 
known as "cement clinker." This clinker drops out of the lower 
end of the kiln, is cooled! so as to prevent injury to the grind- 
ing machinery, and is then sent to the grinding mills. 

Theoretical fuel requirements. As a preliminary to a discus- 
sion of actual practice in the matter of fuel, it will be of interest 
to determine the heat units and fuel theoretically required in the 
manufacture of Portland cement from a dry mixture of normal 
composition. 

In burning such a mixture to a clinker, practically all of the 
heat consumed in the operation will be that required for the dis- 
sociation of the lime carbonate present into lime oxide and car- 
bon dioxide. Driving off the water of combination that is 
chemically held by the clay or shale, and decomposing any cal- 
cium sulphate (gypsum) that may be present in the raw mater- 
ials, will require a small additional amount of heat. The 
amount required for these purposes is not accurately known, 
however, but is probably so small that it will be more or less en- 
tirely offset by the heat which will be liberated during the com- 
bination of the lime with the silica and alumina. We may, 
therefore, without sensible error, regard the total heat theoreti- 
cally required for the production of a barrel of Portland ce- 
ment as being that which is necessary for the dissociation of 450 
pounds of lime carbonate. With coal of a thermal value of 
13,500 B. T. U., burned with only the air supply demanded by 
theory, this dissociation will require 25^2 pounds of coal per 
barrel of cement, a fuel consumption of only 6.6 per cent. 

Losses of heat in practice. In practice with the: rotary kiln, 
however, there are a number of distinct sources of loss of heat, 
which result in a fuel consumption immensely greater than the 
theoretical requirements given above. The more important of 
these sources of loss are the following : 

1. The kiln gases are discharged at a temperature much 
above that of the atmosphere, ranging from 300 F. to 2,000 F., 
according to the type of materials used and the length of the 
kiln. 

2. The clinker is discharged at a temperature varying from 
3OOF. to 2,5ooF., the range depending, as before, on materials 
and length of the kiln. 



53 > 

3. The air supply injected into the kiln is always greater, 
and usually very much greater, than that required for the per- 
fect combusion of the fuel ; and the available heating power of 
the fuel is thereby reduced. 

4. Heat is lest by radiation from the ends and exposed sur- 
faces of the kiln. 

5. The mixture, in plants using a wet process, carries a high 
percentage of water, which must be driven off. 

It is evident, therefore, that present-day working conditions 
serve to increase greatly the amount of fuel actually necessary 
for the production of a barrel of cement above that required by 
theory. 

Actual fuel requirements and output. Rotary kilns are nom- 
inally rated at a production of 200 barrels per day per kiln. 
Even on dry and easily clinkered materials and with good coal, 
however, such an output is not commonly attained with a 
6o-foot kiln, except in the Lehigh) district. Normally 
a kiln working on a dry mixture will produce from 160 to 180 
barrels of cement per day of twenty-four hours. In doing this, 
if good coal is used, its fuel consumption will commonly be 
from 1 20 to 140 pounds of coal per barrel of cement, though it 
may range as high as 160 pounds, and, on the other hand, has 
fallen as low as 90 pounds. An output of 175 barrels per day, 
with a coal consumption of 130 pounds per barrel, may there- 
fore be considered 1 as representing the results of fairly good 
practice on dry materials with a oo-fcot kiln. In dealing with a 
wet mixture, which may carry anywhere from 30 to 70 per cent, 
of w r ater, the results are more variable, though always worse 
than with dry materials. In working a 6o-foot kiln on wet ma- 
terial, the output may range from 80 to 120 barrels per day, with 
a fuel consumption of from 150 to 230 pounds per barrel. Using 
a longer kiln, partly drying the mixture, and utilizing waste 
heat, will of course improve these figures materially. 

When the heavy Western oils are used for kiln fuel, it may 
be considered that one gallon of oil is equivalent in the kiln to 
about ten pounds of coal. The fuel consumption, using dry 
materials, will range between 1 1 and 14 gallons of oil per bar- 
rel of cement ; but the* output per day is always somewhat less 
with oil fuel than where coal is used. 

Natural gas in the kiln may be compared with good Pennsyl- 
vania coal by allowing about 20,000 to 30,000 cubic feet of gas 



54 

as equivalent to a ton of coal. This estimate is, however, based 
upon too little data to be as close as those above given for oil 
or coal. 

Effect of composition on burning. The differences in com- 
position between Portland cement mixtures are very slight if 
compared, for example, to the differences between various nat- 
ural cement rocks. But even such slight differences as do ex- 
ist exercise a very appreciable effect on the burning of the mix- 
ture. Other things being equal, any increase in the percentage 
of lime in the mixture will necessitate 1 a higher temperature in 
order to get an equally sound cement. A mixture which will 
give a cement carrying 59 per cent, of lime, for example, will 
require much less thorough burning than would a mixture de- 
signed to give a cement with 64 per cent, of lime. 

With equal lime percentages, the cement carrying high silica 
and low alumina and iron will require a higher temperature 
than if it were lower in silica and higher in alumina and iron. 
But, on the other hand, if the alumina and iron are carried too 
high, the clinker will ball up in the kiln, forming sticky and un- 
manageable masses. 

Character of kiln coal. The fuel most commonly used in 
modern rotary kiln practice is bituminous coal, pulverized very 
finely. Coal for this purpose should be high in volatile matter, 
and! as low in ash and sulphur as possible. Russell gives the 
following analyses of West Virginia and Pennsylvania coals 
used at present at various cement plants in Michigan. 

Analyses of kiln coals. 

1234 

Fixed carbon 56.15 56.33 55.82 51.69 

Volatile matter 35.41 35.26 39.37 39.52 

Ash 6.36 7.06 3.81 6.13 

Moisture 2.08 1.35 1.00 1.40 

Sulphur 1.30 1.34 0.42 1.46 

The coal as usually bought is either "slack" or "run: of mine." 
In the latter case it is necessary to crush the lumps before pro- 
ceeding further with the preparation of the coal, but with slack 
this preliminary crushing is not necessary, and th? material can 
go directly to the dryer. 



55 

Drying coal. Coal as bought may carry as high as 15 per 
cent, of water in winter or wet season. Usually it will run 
from 3 to 8 per cent. To secure good results from the crush- 
ing machinery it is necessary that this water should be driven 
off. For coal drying, as for the drying of raiw materials, the 
rotary dryer seems best adapted to American conditions. It 
should be said, however, that in drying coal it is usually consid- 
ered inadvisable to allow the products of combustion to pass 
through the cylinder in which the coal is being dried. This 
restriction serves to decrease slightly the possible 'economy of 
the dryer, but an evaporation of 6 to 8 pounds of water per 
pound of fuel coal can still be counted en with any good dryer. 
The fuel cost of drying coal containing 8 per cent, of moisture, 
allowing $2 per ton for the coal used as fuel, will therefore be 
about 3 to 4 cents per ton of dried product. 

Pulverizing coal. Though apparently brittle enough when 
in large lumps, coal is a difficult material to pulverize finely. 
For cement kiln use, the fineness of reduction is very variable. 
The finer the coal is pulverized the better results will be ob- 
tained from it in the kiln ; and the poorer the quality of the coal 
the finer it is necessary to pulverize it. The fineness attained 
may therefore vary from 85 per cent, through a loo-mesh sieve, 
to <)5 per cent, or more, through the same. At one plant a very 
poor but cheap coal is pulverized to pass 98 per cent, through 
;' loo-mesli sieve, and in consequence gives very good results 
in the kiln. 

Coal pulverizing is usually carried on in two stages, the ma- 
terial being first crushed to 20 to 30 mesh in a Williams mill or 
ball mill, and finally reduced in a tube mill. At many plants, 
however, the entire reduction takes place in one stage, Griffin 
or Huntington mills being used. 

Total cost of coal production. The total cost of crushing (if 
necessary), drying and pulverizing coal, and of conveying and 
feeding the product to the kiln, together with fair allowance for 
replacements and repairs, andl for interest on the plant, will 
probably range from about 20 to 30 cents per ton of dried coal, 
for a 4-kiln plant. This will be equivalent to a ccst of from 3 
to 5 cents per barrel of cement. While this may seem a heavy 
addition to the cost of cement manufacture, it should be remem- 
bered that careful drying and fine pulverizing enable the manu- 



56 

facturer to use much poorer and therefore cheaper grades of 
coal than could otherwise be utilized. 

CLiNKER GRINDING. GYPSUM. 

Clinker grinding. The power and machinery required for 
pulverizing the clinker at a Portland cement plant using the dry 
process of manufacture is very closely the same as that required 
for pulverizing the raw materials for the same output. This 
may seem, at first sight, improbable, for Portland cement clinker 
is much hardier to grind than any possible combination of raw 
materials ; but it must be remembered that for every barrel of 
cement produced about 600 pounds of raw materials must be 
pulverized, while only a scant 400 pounds of clinker will be 
treated, and that the large crushers required for some raw ma- 
terials can be dispensed with in crushing clinker. With this ex- 
ception, the raw material side 'and the clinker side of a dry-pro- 
cess Portland cement plant are usually almost or exactly dupli- 
cates. 

The difficulty, and in consequence the expense, of grinding 
clinker will dlepend in large part on the chemical composition of 
the clinker and on the; temperature at which it has been burned. 
The difficulty of grinding, for example, increases with the per- 
centage of lime carried by the clinker ; and a clinker containing 
64 per cent, of lime will be very noticeably more resistant to 
pulverizing than one carrying 62 per cent, of lime. So fair as 
regards burning, it may be said in general, that the more thor- 
oughly burned the clinker the more difficult it will be to grind, 
assuming that its chemical composition remains the same. 

The tendency among engineers at present is to demand more 
finely ground cement. While this demand is doubtless justified 
by the results oi comparative tests of finely and coarsely ground 
cements, it must be borne in mind that any increase in fineness 
of grinding means a decrease in the product per hour of the 
grinding mills employed, and a consequent increase in the cost 
of cement. At some point in the process, therefore, the gain in 
strength due to fineness of grinding will be counterbalanced by 
the increased cost of manufacturing the more finely ground pro- 
duct. 

The increase in the required fineness has been gradual but 
steady during recent years. Most specifications now require at 



57 

least 90 per cent, to pass a loo-mesh sieve; a number require 92 
per cent. ; while a few important specifications require 95 per 
cent. Within a few years it is probable that almost all specifi- 
cations will go as high as this. 

Addition of gypsum. The cement produced by the rotary 
kiln is invariably naturally so quick-setting as to require the 
addition of sulphate of lime. This substance, when added in 
quantities up to 2 l / 2 or 3 per cent., retards the rate of set of the 
cement proportionately, and appears to exert no injurious influ- 
ence on the strength of the cement. In amount over 3 per cent., 
however, its retarding influence seems to become at least doubt- 
ful, while a decided weakening of the cement is noticeable. 

Sulphate of lime may be added in one of two forms : either 
as crude gypsum or as burned plaster. Crude gypsum is a 
natural hydrous lime sulphate, containing about 80 per cent, of 
lime sulphate and 20 per cent, of water. When gypsum is cal- 
cined at temperatures not exceeding 4OOF., most of its contain- 
ed water is driven off. The "plaster" remaining carries about 
93 per cent, of lime sulphate, with only 7 per cent of water. 

In Portland cement manufacture either gypsum or burned 
plaster may be used to retard the set of the cement. As a mat- 
er of fact, gypsum is the form almost universally employed in 
the United States. This is merely a question of cost. It is true 
that to secure the same amount of retardation of set it will be 
r.ecessary to add a little more of gypsum than if burned plaster 
were used ; but, on the other hand, gypsum is much cheaper 
than burned plaster. 

The addition of the gypsum to the clinker is usually made 
before it has passed into the ball mill, komminuter, or whatever 
mill is in use for preliminary grinding. Adding it at this point 
secures much more thorough mixing and pulverizing than if 
the mixture were made later in the process. At some of the 
few plants which use plaster instead of gypsum, the finely 
ground plaster is not added until the clinker has received the 
iinal grinding and is ready for storage or packing. 

CONSTITUTION OF PORTLAND CEMENT. 

During recent years much attention has been paid by various 
investigators to the constitution of Portland cement. The 
chemical composition of any particular sample can, of course, be 



58 

readily determined by analysis ; and by comparison of a number 
of such analyses, general statements can be framed as to the 
range in composition of good Portland cements. 

The chemical analyses will determine what ingredients are 
present, and in what percentages, but other methods of investi- 
gation are necessary to ascertain in what manner these various 
ingredients are combined. A summary of the more important 
results brought out by these investigations on the constitution 
of Portland cement is here given. 

It would seem to be firmly established that, in a well-burned 
Portland cement, much of the lime is combined with most of 
the silica to form the compound 3 CaO, SiO2, tricalcic silicate. 
To this compound is ascribed, in large measure, the hydraulic 
properties of the cement ; and in general it may be said that the 
value of a Portland cement increases directly as the proportion 
of 3 CaO, SiO2. The ideal Portland cement, toward which ce- 
ments as actually made tend in composition, would consist ex- 
clusively of tricalcic silicate, and would be therefore composed 
entirely of lime and silica in the following proportions : 

Lime (CaO) 73.6 

Silica (SiO2) 26.4 

Such an ideal cement, however, can not be manufactured 
under present commercial conditions, for the heat required to 
clinker such a mixture can not be attained in any working kiln. 
Newberry has prepared such mixtures by using the oxy-hydro- 
gen blowpipe; and the electrical furnace will also give clinker 
of this composition ; but a pure lime-silica Portland is not pos- 
sible under present-day conditions. 

In order to prepare Portland cement in actual practice, there- 
fore, it is necessary that some other ingredient or ingredients 
should be present to serve as a flux in aiding the combination of 
the lime and silica, and such aid is afforded by the presence of 
alumina and iron oxide. 

Alumina (A12O3) and iron oxide (Fe2O3), when present in 
noticeable percentages, serve to reduce the temperature at which 
combination of the lime and silica (to form 3 CaO, SiO2) takes 
place ; and this clinkering temperature becomes further and fur- 
ther lowered as the percentages of alumina and iron are in- 
creased. The strength and value of the product, however, also 
decrease as the alumina and iron increase ; so that in actual 



59 

practice it is necessary to strike a balance between the advantage 
of low clinkering temperature and the disadvantage of weak 
cement, and to thus determine how much alumina and iron 
should be used in the mixture. 

It is generally considered that whatever alumina is present 
in the cement is combined with part of the lime to form the 
compound 2 CaA, SiO2, dicalcic aluminate. It is also held 
hy some, but this fact is somewhat less firmly established than 
the last, that the iron present is combined with the lime to 
form the compound 2 CaO, Fe2O3. For the purposes of the 
present paper, it will be sufficient to say that, in the relatively 
small percentages in which iron occurs in Portland cement, it 
may for convenience be considered as almost equivalent to 
alumina and its action, and the two may be calculated together. 



PART II. 



THE CEMENT RESOURCES OF ALABAMA. 



BY SUGDNF, A. SMITH. 



In Alabama is found an extensive series of limestones capable 
of furnishing excellent raw material for the manufacture of 
Portland cement, while the shales and clays necessary to com- 
plete the mixture are found in every county in the State. As 
a matter of convenience, the Portland cement materials of north- 
ern Alabama and of central and southern Alabama will be dis- 
cussed separately, because there is a marked geologic as well 
; s geographic distinction between the two portions of the State. 



CHAPTER 1. 

THE PORTLAND CEMENT MATERIALS OF NORTH- 
ERN ALABAMA. 

The raw materials for the manufacture of Portland cement 
occurring in the Paleozoic formations of northern Alabama are 
limestones, shales, and clays. Of these the limestones belong 
mainly to the Lower Carboniferous and the Trenton forma- 
tions; the shales to the Coal Measures, and the clays to the 
Cambrian, Lower Carboniferous, and Coal Measures. Al- 
though as yet these materials have not been utilized for this 
purpose in Alabama, they have been so used in other States, 
and there is no reason to doubt that the future will witness 
their utilization in Alabama. 



62 

AVAILABLE LIMESTONES. 

General geology. In northern Alabama the combined effects 
of geologic structure and erosion have resulted in certain defi- 
nite topographic types, with which the geologic outcrops are 
closely connected. 

Structurally northern Alabama is made up of a series of paral- 
lel synclines and anticlines, trending usually a little north of east. 
The anticlines are sharp, narrow folds; the synclines are flat, 
wide basins. The effect of erosion has been to cut away the 
anticlines and the streams of the region now run along anticlinal 
valleys bordered by flat-topped synclinal plateaus. 

The plateaus throughout most of northern Alabama are 
capped by conglomerates, shales, and sandstones of the Coal 
Measures. The lower Carboniferous limestones 'commonly 
outcrop along the sides and at the immediate base of the 
plateaus. The lower Silurian beds occur as long, narrow out- 
crops in the valleys. The middle of the valley is usually occu- 
pied by Cambrian shales and the Knox dolomite. The Tren- 
ton limestones would normally outcrop as two parallel bands in 
each valley between the middle of the valley and the foothills 
of the plateaus. Faulting has, however, been so common that 
only one of these bands is usually present, the other being cut 
out by a fault. 

Lower Carboniferous. Limestones of suitable quality for 
cement manufacture occur in the Mountain limestone or Ches- 
ter formation of the lower Carboniferous. Perhaps the most 
accessible occurrences of this rock are in the Tennessee Valley 
to the west of Tuscumbia and south of the river and railroad. 
Here the quarries of Fossick & Co. were formerly located. 
Their quarries at this time are farther eastward, but at a greater 
distance from the river, in Lawrence county north of Russell- 
ville. This outcrop extends thence eastward along the base 
of Little Mountain as far as Whitesburg, above which place 
to Guntersville the river flows through a valley floored with 
lower Carboniferous limestone. The Southern Railway passes 
over outcrops of this rock in most of the mountain coves east 
of Huntsville, and from Scottsboro to the Tenneissee line the 
country rock is almost entirely of this formation. The Louis- 
ville and Nashville Railroad south of Decatur nearly to Wilhite 
is mostly in the same formation. These two lines, together 



with the Tennessee river, would provide ample means of trans- 
portation for the rock or for the finished product. Analysis of 
the rock from the Fossick quarries is given in Table A. 

In Browns Valley south of Brooksville the Mountain lime- 
stone is the prevailing reck across the valley, and at Bangor 
and Blount Springs, on the Louisville! and Nashville Railroad, 
there are extensive quarries which have been worked for many 
years to supply rock for fluxing purposes to the furnaces of the 
Birmingham district. Analyses Nos. 2, 3, 4, 5, 6, 7, 8, and 9, 
Table A, show the composition of average samples from these 
quarries ; 5 to 9, inclusive, are of carload samples. 

From Brooksville to the Tennessee line a great thickness of 
this limestone is exposed along the western escarpment of Sand 
Mountain, below the sandstones of the Coal Measures, which 
there cap the mountain. In this area the river runs near the 
foot of the mountain and would afford the means of transpor- 
tation. 

In similar manner the lower Carboniferous limestone out- 
crops along the western flank of Lookout Mountain in Little 
Wills Valley, from near Attalla to the Georgia line, and south 
of Attalla it forms the lower part of the escarpments of Blount 
and Chandlers Mountains. The Alabama Great Southern Rail- 
road passes very near to the outcrop from the Georgia line down 
to Springville, Ala. South of Springville large outcrops oc- 
cur in Shades Valley, and at Trussville are quarries which hav;e 
supplied the Birmingham furnaces. Analyses 10 to 17, inclu- 
sive. Table A, are of material from Trussville; and analyses 12 
to 17, inclusive, represent average samples from carload lots 
delivered to the furnace. 

In Murphrees Valley the main outcrop of this rock is on the 
western side, and quarries at Compton have for many years 
been worked to supply the Birmingham furnaces. Analyses 
i8 } 19, and 20, Table A, of the rock from these quarries show 
somewhat varying composition, but by proper selection suitable 
material could be easily obtained. 

In the valleys lying east of Shades Valley and in parts of 
Shades Valley itself this formation becomes one of prevailing 
shales and sandstones and the limestones are of limited occur- 
rence and of inferior quality. 

Trenton limestone. The Trenton limestone outcrops in Ala- 
bama in three principle areas. In the Tennessee River Valley 



64 

some of the smaller streams which flow into the river from the 
north, like Flint River, Limestone Creek, Elk River, Bluewater 
Creek, and Shoal Creek, have eroded their valleys into the Tren- 
ton limestone. These areas are crossed at only a few points by 
the railroads leading out from Huntsville and Florence, and no 
commercial use has yet been made of the rock. 

In the narrow anticlinal valleys below enumerated erosion 
has in most cases sunk the floors of the valleys into Cambrian 
strata, and, as a consequence, the Trenton limestone occupies a 
narrow belt on each side, near the base of the Red Mountain 
ridges. But since a fault usually occurs on one side of these 
valleys, the Red Mountain ridges and the accompanying Tren- 
ton limestone are mere fully represented on the unfaulted side, 
which is the eastern side in all except Murphrees Valloy. While 
the Trenton forms practically a continuous belt along the un- 
disturbed side, extensive areas are sometimes found on the 
faulted side also. This is the case, for instance, at Vance, on 
the Alabama Great Southern Railroad, where the rock is quar- 
ried for flux for the furnace of the Central Iron Company at 
Tuscaloosa. Analysis I of Table B, shows its composition 
here. Other series of analyses from lower ledges in the quarry 
show only 1.22 per cent of silica, but more magnesia. 

In cases where erosion has not gone so deep as to reach the 
Cambrian the Trenton may be found extending entirely across 
the valleys. This is the case in the lower part of Browns Valley 
from Brooksville to beyond Guntersville. Above Guntersville 
the Trenton is seen mainly on the eastern side of the valley. 
The river touches these outcrops at many points, and at Gun- 
tersville the railroad connecting that city with Attalla would 
afford an additional means of transportation. No develop- 
ments have yet been made in this area. 

The valley separating the Warrior irom the Cahaba coal 
field is known as Roups Valley in the southern and as Jones 
Valley in the, northern part. In these the Trenton occupies a 
narrow, continuous belt, usually near the base of the eastern 
Red Mountain ridge, though in places it is high up on the ridge 
and .even at its summit, as at Gate City, where the quarries of 
the Sloss Iron Company are located. Many analyses of 
the rock from these quarries have been made, and several are 
given in Table B, (Nos, 2, 3, 4, 5, 6). 



65 

In Murphrees Valley the continuous belt of the Trenton, as 
above explained, is on the western side, while the faulted rem- 
nants are on the eastern side. No quarries have been opened 
.in the Trenton limestone here, but the Louisville and Nashville 
Railroad goes u'p the valley as far as Oneonta and would afford 
means of transportation. 

In the Cahaba Valley, which separates the Cahaba coal field 
from the Coosa coal field, the Trenton is well exposed on the 
eastern side for the entire length of the valley from Gadsden 
down. It expands into wide areas near the southern end, where 
it has been quarried for lime burning, at Pelham, Siluria, Long- 
view, Calera, and other places on the line of the Louisville and 
Nashville road. Analyses 7, 8 and 9 of Table B, show the com- 
position of the rock in this region. 

The Central of Georgia and the Southern railroads cross this 
belt about midway of its length at Leeds, in Jefferson County, 
and near its northern end it is crossed by the Louisville and 
Nashville Railroad, where a quarry at Rock Springs, on thte 
flank of Colvin Mountain, supplies the rock for lime burning. 
Anaylsis 10 shows the character of the rock at this point. 

At Pratts Ferry, on the Cahaba. River, a few miles above 
Centreville, in Bibb County, the Trenton limestone makes high 
bluffs along the river for several miles, and is in most conven- 
ient position for easy quarrying. 

Marble works have in former days been established here and 
should be again put in operation, since the marble is of fine 
quality and beautifully variegated. No analyses are avail- 
able, but there is no doubt that much of the rock is sufficiently 
low in magnesia to be fit for use in cement making. Cahaba 
River and a short spur from the Mobile and Ohio Railroad 
would afford transportation facilities for this deposit. 

In Big Wills Valley, which separates Sand and Lookout 
mountains, the Trenton limestone occupies perhaps 25 square 
miles, but it is crossed only by the railroad connecting Gadsden 
with Guntersvlile. No anaylses are available. 

In the great Coosa Valley region the Trenton outcrops are 
found mostly on the western border near the base of Lookout 
Mountain, as in Broomtown Valley, and in other valleys ex- 
tending south toward Gadsden. While these belts have been 
utilized in the past for the old Gaylesville, Cornwall, and Round 



66 

Mountain furnaces, and possibly for some furnaces now in blast, 
no analyses are available. 

Similarly, farther south, along this western border of the 
Coosa Valley, and running parallel with the Coosa coal field in 
Calhoun, St. Clair, and Shelby counties, there are numerous 
long narrow outcrops of Trenton limestone. The Calcis quarry 
of the Tennessee Coal, Iron and Railroad Company, on the Cen- 
tral of Georgia Railroad, near Sterritt, is upon one of these 
outcrops, and furnishes limestone with a very low and uniform 
percentage of silica and magnesia. Analyses n, 12, 13, 14, 15, 
and 1 6 exhibit the quality of the reck as received at the Ensley 
Steel Works, but care is taken at the quarry- to select ledges low 
in silica and magnesia, and the analyses therefore represent 
only the selected ledges and not the average run of the quarry 
as a whole. 

Near Talladega Springs, Marble Valley, and Shelby are 
other occurrences of the rock, and a quarry a few. miles east of 
Shelby furnace has for many years supplied that furnace with 
its flux. The quality of the material here is shown by analyses 
17, 1 8, 19, and 20, Table B. 

The Cambrian limestones contain generally a very considera- 
ble proportion of magnesia, and for this reason are not suited 
for Portland-cement manufacture, though admirably adapted 
for furnace stone. 

Marbles. Along the eastern border o>f tht Coosa Valley, 
near its contact with the metamorphic rocks, there is a belt of 
limestone which, in places, is a white crystalline marble of great 
purity, as is shown by analyses I to 7, inclusive, o-f Table C. 
The Louisville and Nashville Railroad, from Calera to Talla- 
dega, passes close to this belt at many points. This marble has 
been quairried at several places for ornamental stone. It is 
mentioned here because it is near the railroad and completes the 
account of the limestone. 

THE CLAYS. 

The most important clays in the Paleozoic region occur in the 
Coal Measures, in the Lower Carboniferous, and in the Lower 
Silurian and Cambrian formations. But, inasmuch as a later 
formation the Tuscaloosa of the Cretaceous borders the 
Paleozoic on the west and south, and as it contains a great vari- 



67 

ety as well as abundance of clays, we shall include it here, al- 
though it is not one of the Paleozoics. 

Coal Measures. In this group are numerous beds of shale 
which have been utilized in the manufacture of vitrified brick 
and fire brick, but many of them will probably be adapted to ce- 
ment making. A great body of these shales occurs in connec- 
tion with the coal seams of the Horse Creek or Mary Lee group, 
in Jefferson and \Yalker counties, and in position where they 
are conventienly situated with reference to limestone and coal 
and also tot transportation lines. They are therefore well worth 
the attention of those contemplating the location of cement 
plants. 

On the property of Mr. W. H. Graves, near North Birming- 
ham, overlying the coal seam mined by him, there are two beds 
of shale one yellowish, the other gray. These two shales have 
been tested and analyzed, and their composition is shown in 
Nos. i and 2 of the Table D. 

Similar shales are known to occur at Coaldale, in Jefferson 
County, at Pearce's Mills in Marion, and at Cedar Grove Coal 
Mines in Tuscaloosa. The Coaldale shale is manufactured 
into vitrified brick. The other two have not yet been utilized. 

Analyses 3 and 4 of Table D will showi the composition of 
the shales at Coaldale and Cedar Grove. 

It may be of interest to note that Cedar Grove is, so far as 
yet known, the nearest place to the Gulf ports, where the three 
essentials in the manufacture of Portland cement, viz., limestone, 
shale and coal, occur together, and on a railroad. 

So also most of the coal seams mined in Alabama rest upcn 
clay beds which have not as yet been specially examined as to 
their fitness for cement making; but, in view of the proximity 
of the coal mines to the limestones, it might be worth while to 
investigate these underclays of the coal seams. 

Lower Carboniferous. Associated with the cherty lime- 
stones of the lowermost division of the Lower Carboniferous of 
some of the anticlinal valleys are beds of clay of excellent qual- 
ity, much of it being of the nature of china clay. 

Probably the best of the exposures of these clays are to be 
seen in Little Wills Valley, between Fort Payne and the Geor- 
gia border, and on the line of the Great Southern Railroad, 
where for many years quarries have been in operation in sup- 



68 

plying the material for tile works and potteries. The clays lie 
near the base of the formation close above the black shale of 
the Devonian, and average about 40 feet in thickness, though 
in places they reach 200 feet. The clay bed : s alternate with 
seams of chert which are from 2 to 8 inches in thickness, while 
the clay beds vary from 12 to 18 inches. The upper half of 
the clay is more gritty than the lower half which often contains 
material suitable for the manufacture of the finer grades of 
porcelain ware. Analyses 5 to 8, in Table D, show the com- 
position of several varieties of clay from this section. 

Lower Silurian and Cambrian. Associated with the cherty 
limestones and brown iron-ore beds of the formations above 
named beds of fine white clay, much of it china clay are not 
uncommon. Analysis 9 of the table shows the composition of 
a white clay from the brown ore bank at Rock Run, in Cherokee 
County, where the clay is about 30 feet in thickness. Analyses 
10 and ii are also from Rock Run. No. 12, from near Gads- 
den, No. 13, from Blount County, and No. 14 from Oxanna, in 
Calhoun County, are clays which seem to be adapted to cement 
making. While no great number of the clays of these forma- 
tions have been analyzed, they are known to be widely distrib- 
uted 1 in Calhoun', Talladega, Jefferson, Tuscaloosa, and other 
counties in connection with the browtn ore deposits. 

Cretaceous. In many respects the most important formation 
of Alabama, in respect of its clays, is the lowermost division 
of the Cretaceous, which has been called the Tuscaloosa, and 
which is in part at least of the same geologic horizon as that of 
the Raritan clays of New Jersey. The prevailing strata of this 
formation are yellowish and grayish sands, but subordinated 
to them are great lenses of massive clay varying in quality from 
almost pure-white burning clay to dark-purple and mottled va- 
rieties high in iron. 

The formation occupies a belt of country extending from 
the north-western comer of the State, around the edges of the 
Paleozoic formations to the Georgia line at Columbus. Its 
greatest width is at the northwest boundary of the State where 
it covers an area 30 or 40 miles wide in Alabama, and of about 
the same width in Mississippi. The breadth at Wetumpka and 
thence eastward to the Georgia line is only a few miles. The 
most important part of this belt is where it is widest in Elmore, 



GO 

Bibb. Tuscaloosa, Pickens, Fayette, Marion, Lamar, Franklin, 
and Colbert counties, and the deposits are traversed by the lines 
of the Mobile and Ohio; the Alabama Great Southern; the 
Louisville and Nashville; the Southern; and the Kansas City, 
Memphis and Birmingham railroads ; as well as by the Warrior 
and Tombigbee rivers. 

These clays have been described in some detail, and many 
analyses and physical tests have been presented in the Bulletin 
No. 6 of the Alabama Geological Survey. From this bulletin 
have been selected the analyses which appear to indicate the 
fitness of the clays for cement making. 

In Elmore county, in the vicinity of Coosada, along the banks 
of the river, about Robinson Springs, Edgewood, and Chalk 
Bluff, there are many occurrences of these clays, some of which 
have been used in potteries for many years. Analyses 15, from 
Coosada; 16, from Edgewood; and 17, from Chalk Bluff, are 
given in the table D. 

In Bibb county the clay has been quarried viery extensively at 
Bibbville and near Woodstock for making fire brick. For this 
purpose the material is carried to Bessemer by the Alabama 
Great Southern Railroad. No. 18, from Woodstock; and 19, 
from Bibbville, will represent the average quality of the clay 
from these beds, which are very extensive, both in thickness 
and in superficial distribution. The Mobile & Ohio crosses 
other extensive deposits in the southern part of the county, but 
no analyses are available. 

The most important of the clay beds in Tuscaloosa county 
are traversed by the Mobile & Ohio Railroad and by the Ala- 
bama Great Southern. 

Analysis 20, from Hull's; and analysis 21, from the Cribbs 
beds, are on the Alabama Great Southern; and 22 and 23 are 
from cuts of the Mobile & Ohio, a few miles west of the city of 
Tuscalcosa. 

Many large beds are exposed along the Mobile & Ohio road 
in Pickens county also, but very few haive been as yet investi- 
gated. No. 24 is from Roberts Mill, in this county. 

In Lamar and Fayette counties the same conditions prevail as 
in Pickens and Tuscaloosa, Analysis 25 is of pottery clay from 
the Cribbs place, in Lamar ; and No. 26 is of clay from Wig- 
gins's, 4 miles west of Fayette ; and 27 and 28 are clays from 
W. Doty's place, 14 miles west of that town, in Fayette county. 



70 

Marion is one of the banner counties of the State for fine 
clays, but it is touched by railroads only along its southern bor- 
der and "n the extreme northeastern corner. Although at pres- 
ent not available because inaccessible, the clays mentioned be- 
low are worth consideration : No. 29, from Glen Allen ; No. 30, 
from Briggs Fredericks', in Sec. 8, T. 10, R. 13 W. This is from 
the great clay deposit which gives the name to Chalk Bluff and 
which underlies about two townships. No. 31 is from a local- 
ity about 1 6 miles southwest of Hamilton, the county seat. 

No. 32 is from a locality near the Mississippi line, in section 
20, T. 8, R. 15 W., in Franklin county, from land of Mr. Thom- 
as Rollins. 

Of the numerous fine clays of Colbert county analyses are 
given of two from Pegram station, on the Southern Railway, 
near the Mississippi State line. These are Nos. 33 and 34. 



71 



Table A. 
Analyses of Lower Carboniferous Limestones. 



Number. 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 




Pr ct 


Pr ct 


Prct 


Pr ct 


Pr ct 


Prct 


Pr ct 


Pr ct 


Pr ct 


Pr ct 


Silica 


0.50 


1.73 


0.77 


1.14 


1.02 


1.40 


0.68 


0.81 


0.82 


2.16 


Iron and alumi- 






















num oxide 


1.45 


.78 


.35 


.34 


1.38 


1.17 


1.02 


.89 


.60 


2.31 


Calcium carb'te. 


96.58 


98.54 


97.60 


98.53 


95.25 


94.67 


96.54 


97.45 


97.37 


89.15 


Magnesium carbt 


2.58 








1.73 


2.26 


1.26 


.35 


.75 


4.20 


Sulphur 



















.029 




Number. 


11 


12 


13 


14 


15 


16 


17 


18 


19 


20 












I, 












Pr ct 


Pr ct 


Prct 


Prct 


Prct 


Prct 


Prct 


Pr ct 


Pr ct 


Pr ct 


Silica 


3.12 


0.85 


1.08 


0.73 


0.64 


1.12 


0.42 


2.05 


4.45 


2.80 


Iron and alumi- 






















num oxide 


2.32 


.65 1 .61 


.65 


.62 


.90 


.37 


.76 


3.30 


.70 


Calcium carb'te. 1 85. 87 |93.64 jflfi.OI 


97.60 (97.48 


96.38 


97.32 (89.64 


86.35 


94.59 


Magnesium carbt! 4.20 


1.36 


.90 


.52 


.76 


1.10 


1.39 


8.15 






Sulphur 





.024| - .019] .0181 




.020 










1. Average sample from Fossick quarry, near Rockwood, Franklin 
County. Government Arsenal, Watertown, N. Y.. analyst. 

2. Average sample from Blount Springs quarry a compact limestone. 
Henry McCalley, analyst. 

3. Average sample from Blount Springs quarry a granular oolitic lime- 
stone. Henry McCalley, analyst. 

4. Average sample upper 75 feet, Blount Springs quarry. J. L. Beeson, 
analyst. 

5-9. Average sample Blount Springs quarry. J. R. Harris, analyst. 

10. 11. From Worthington quarry, near Trussville, Jefferson county. 
C. A. Meissner, analyst. 

12-17. From Vanns, near Trussville. J. R. Harris, analyst. 

18. Average of about 150 feet thickness of rock used for flux, Compton 
quarry. Blount county. J. L. Beeson, analyst. 

19, 20. Stockhouse sample. Compton quarry. Wm. B. Phillips, analyst. 



72 



Table B. 

Analyses of Trenton Limestones. 



Number. 


1 


2 


3 


4 


5 


6 


7 


8 


9 


.10 




Pr ct 


Pr ct 


Pr ct 


Prct 


Pr ct 


Prct 


Pr ct 


Pr ct 


Pr ct 


Pr ct 


Silica 


4.48 


5.70 


2.43 


3.65 


3.29 


3.82 


0.39 


0.15 


0.78 


1.00 


Iron and alumi- 






















num oxides 
Calcium carb'te. 
Magnesium carbt 


1 22 

88.85 
3 52 


1.87 
91.16 


3.30 
89.88 


.91 
92.38 


1.49 
92.61 


1.96 
90.44 


.13 

99.11 
75 


Tr 
99.16 

75 


.35 
97.52 

1 27 


.30 
97.00 
Tr 


Sulphur 




















Tr 


Water, organic 
matter and loss 












































Number. 


11 


' 
12 


13 


14 


15 


16 


17 


18 


19 


20 


Silica 


Pr ct 
43 


Pr ct 

58 


Pr ct 
38 


Prct 
34 


Pr ct 

39 


Prct 

98 


Pr ct 

2 50 


Pr ct 

9 09 


Pr ct 
1 08 


Pr ct 

2 9 5 


Iron and alumi- 






















num oxides 


.42 


.25 


.47 


.46 


.37 


.52 


1.40 


1.01 


.63 


.68 


Calcium carb'te. 


98.49 


95.78 


98.35 


96.53 


94.27 


96.92 


96.70 


93.77 


98.91 


95.40 


Magnesium carbt 
Sulphur 


.16 


2.89 


.30 


2.17 


4.47 


1.08 




2.48 


.58 


.94 


Water, organic 
matter and loss 
























1. Average of several carloads flux rock from quarry at Vance, Tus- 
caloosa county, of Central Iron Company at Tuscaloosa. H. Buel, an- 
alyst. 

2. Gate City quarry, Jefferson county. Average sample from the 
crusher. Henry McCalley, analyst. 

3-6. Gate City quarry. J. W. Miller, analyst. 

7, 8. Longview quarries, Shelby county. Used in lime burning. Re- 
port of Alabama State Geologist, 1875. 

9. Jones quarry, near Longview. Report of Alabama State Geoligist, 
1875 

10. Rock Spring quarry, Etowah county. Used in lime burning and for 
flux. Wm. B. Phillips, analyst. 

11-16. Rock from Calcis quarry, St. Glair county. J. R. Harris, analyst. 
17-20. Shelby quarry, Shelby county. Used for flux in Shelby furnaces. 
Report of Alabama State Geologist, 1875. 



73 



Table C. 
Analyses of Crystalline Marbles. 



Number. 


1 


2 


3 


4 


5 


6 


7 


Silica 


Pr ct 
Tr 


Pr ct 

2.70 


Pr ct 
2.95 


Prct 

4.65 


Pr ct 

2.80 


Prct 
1.35 


Pr ct 

0.28 


Iron and aluminum oxides 
Calcium carbnate 


99 47 


.40 
90 80 


1.15 
95 25 


.75 
94 40 


.48 
95 60 


.30 
97.60 


.28 
99 19 


Magnesium carbonate 


.38 


Tr 


.62 


.41 


.66 


Tr 


.14 



1. Herd's upper quarry, Talladega county. Tuomey's Second Report. 

2. Heard's quarry, sec. 16, T. 21, R. 4 E., Talladega county. Wm. B. Phil- 

lips, analyst. 

3. Taylor's mill, Talladega county, white marble. Wm. C. Stubbs, analyst. 

4. Taylor's mill, Talladega county, blue marble. Wm. C. Stubbs, analyst. 

5. Taylor's mill, Talladega county. A. F. Brainerd, analyst. 

6. Nix quarry, sec. 36, T. 20, R. 4 E., Talladega county, white marble. Wm. 

B. Phillips, analyst. 

7. Gannt's quarry, sec. 2, T. 22, R. 3 E., Talladega county, white marble. 

A. F. Brainerd, analyst. 



Table D. 
Analyses of Clays Paleozoic and Lower Cretaceous. 



Number. 


1 


o 


3 


4 


5 


6 


7 


s 


, 


Silica 


Pr ct 
61.55 


Pr ct 

57 80 


Prct 

57 22 


Pr ct 

58 50 


Prct 

79 80 


Pr ct 

82 04 


Prct 

66 25 


Pr ct 

go n 


Pr ct 

60 50 


Alumina 
Ferric oxide 
Lime . . 


20.25 
7.23 
Tr 


25.00 
4.00 
2 10 


24.72 
7.14 

4i 


18.28 
10.22 
1 19 


11.75 
1.75 
75 


12.17 
Tr 
Tr 


22.90 
1.60 
Tr 


11.41 
1.40 
Tr 


26.55 
.30 
90 


Magnesia 
Alkalies 
Ignition 


.99 
1.25 
6 19 


.80 
1.80 
7 50 


1.88 
.40 
7 09 


1.40 
.70 


Tr 
1.50 
4 11 


.33 
.60 
4 33 


Tr 
.75 
9 05 


.66 
1.80 
4 00 


.65 
2.70 

7QA 
























98.66 


99.00 


98.93 





99.16 


99.47 


100.55 


101.38 


99.50 



74 



Number. 


10 


11 


12 


13 


14 


15 


16 


17 


18 


Silica 


Pr ct 

72.20 
22.04 
.16 

.50 
.40 
.60 
5.80 


Pr ct 
57.00 
17.80 
5.60 
2.10 
1.20 
6.00 
9.45 


Prct 
67.95 

20.15 
1.00 
1.00 
Tr 
1.87 
8.00 


Pr ct 
61.50 
26.20 
2.10 
.50 
.43 
.70 
7.29 


Pr ct 

84.21 
9.75 
.69 
.70 
.14 

4.10 


Pr ct 

66.61 
21.04 

2.88 
.40 
.58 
.70 
7.00 


Prct 
62.60 
26.98 
.72 
.40 
.36 
.65 
9.30 


Pr ct 
60.38 
20.21 
6.16 
.09 

1.80 
10.21 


Prct 
65.82 
24.58 
1.25 

Tr 

.60 
8.16 


Alumina 


Ferric oxide 
Lime 
Magnesia 


Alkalies 
Ignition 


101.70 


99.15 


99.97 


98.72 


99.59 


99.21 


101.01 


99.57 


100.41 


Number. 


19 


20 


21 


22 


23 


24 


25 


26 


27 


Silica 

Alumia . . . 


Pr ct 

74.25 
17.25 
1.19 
.40 
Tr 
.52 
6.30 


Pr ct 
61.25 
25.60 
2.10 
.25 
.82 
1.35 
8.10 


Prct 
65.35 
21.30 

2.72 
.60 
.86 
Tr 
8.79 


Prct 
60.03 
24.66 
3.69 
.13 
.38 
Tr 
11.34 


Pr ct 
58.13 

24.68 
3.85 
.15 
.32 
1.78 
11.78 


Pr ct 

68.23 
20.35 
3.20 
.34 
Tr 
.74 
7.16 


Prct 
60.90 
18.98 
7.68 
Tr 
Tr 
Tr 
13.36 


Pr ct 
63.27 
19.68 
3 .52 
1.30 
Tr 
1.20 
9.80 


Pr ct 
67.10 

19.37 
2.88 
Tr 
.73 
.67 
7.79 


Ferric oxide 


Lime 
Magnesia 


Alkalies 
Ignition 




99.39 


99.47 


99.62 


100.23 


1.00.51 


100.02 


100.92 


98.77 


98.54 


Number. 


28 


29 


30 


31 


32 


33 


34 






Silica 


Pr ct 

65.58 
19.23 
4.48 
Tr 
Tr 


Pr ct 
68.10 
21.89 
2.01 
.80 
.28 
.40 
5.75 


Prct 

65.49 
24.84 
Tr 
1.26 
Tr 
Tr 
7.80 


Prct 

70.00 
21.31 
2.88 
.20 
Tr 
Tr 
6.85 


Pr ct 

67.50 
19.84 
6.15 
.12 
.10 

7.65 


Pr ct 
66.45 
18.53 
2.40 
1.50 
1.25 
Tr 
9.46. 


Prct 
64.90 
25.25 
Tr 
Tr 
Tr 

8.90 






Alvmina . . ." 


Ferric oxide 


Lime 


Magnesia 
Alkalies 


Ignition 


6.90 


96.19 


99.23 


99.39 


101.24 


101.36 


99.59 


99.05 







( 1. Dark yellow shale from Coal Measures, W. H. Graves, 

near Birmingham, Jefferson county. 

Coal I 2. Light gray shale from same locality. 

Measures.. { 3. Shale from Coaldale, Jefferson county. Analysis by F. 

W. Miller. 

4. Shale over coal seam, Cedar Grove Coal Mines, near 
Vance, Tuscaloosa county. 



Lower Car- 
boniferous 



Fire clay, near Valley Head, DeKalb county. 
China clay, Eureka mines, DeKalb county. 



75 



9. China clay, Rock Run, Cherokee county (Dyke's ore 

bank.) 

I- . Fire clay, Rock Run, Cherokee county. 

Silurian and ! 11. Pottery clay, Rock Run, Cherokee county. 

Cambrian, j 12. China clay, J. R. Hughes, Gadsden, Etowah county. 

13. Stoneware clay, Blount county. 

14. Stevens, Fire clay. Oxanna, Calhoun county; prob- 

bably too much free sand. 

15. Stoneware clay, Coosada, Elmore county. 

16. Pottery clay, McLean's, near Edgewood, Elmore co. 

17. Stoneware clay, Chalk Bluff, Elmore county. . 

18. Fire clay, Woodstock, Bibb county. 

19. Fore clay, Bibbville, Bibb county. 

20. Fire clay. Hulls Sta'n., A. G. So. R. R. Tuscaloosa co. 

21. Pottery clay, H. H. Cribbs, A. G. So. R. R., Tusca- 

loosa county. 

22. Pottery cl.-iy, J. C. Bean. M. & O. R. R., Tuscaloosa co. 

23. Fire clay. J. C. Bean, M. & O. R. R., Tuscaloosa co. 

24. Stoneware clay, Roberts' Mill, Pickens county. 

25. Pottery clay, Cribbs' place, Lamar county. 
23. Stoneware clay, H. Wiggins, Fayette county. 
27-23. Pottery clay, W. Doty, Fayette county. 

29. Bme clay, R. R. cut, near Glen Allen, Marion county. 

30. China clay, Briggs Frederick, Marion county. 

31. Pottery clay, 10 miles S. W. Hamilton, Marion co. 

32. Pottery clay, Thos. Rollins, Franklin county. 

33. Pottery clay, J. W. Williams, Pegram, Colbert co. 

34. China clay, Pegram, Colbert county. 



Lower Cre- 
taceous 
(Tuscaloosa) 



CHAPTER II. 

THE PORTLAND CEMENT MATERIALS OF CEN- 
TRAL AND SOUTHERN ALABAMA. 

The raw materials suitable for the manufacture of Portland 
cement, which occur in Central and Southern Alabama, are ar- 
gillaceous limestones, purer limestones, and clays. 

The limestones valuable as cement materials occur mainly 
at two horizons, viz., in the Selma chalk or Rotten limestone 
of the Cretaceous, and in the St. Stephens formation of the 
Tertiary. The clays available are residual clays from the de- 
composition of the two limestone formations above mentioned, 
the stratified clays of the Grand Gulf formation, and alluvial 
clays occurring in the river and creek bottoms. It is further 
possible that later investigation may show that some of the 
other stratified clays of the Tertiary formations are suitable, 
and this is especially likely to be the case with the clays of the 
lowermost Cretaceous or Tuscaloosa formation. 

THE SELMA CHALK OR ROTTEN LIMESTONE. 

Geological horizon. The Cretaceous system in Alabama is 
susceptible of classification into four divisions, which are, in 
ascending order, 

1, the Tuscaloosa, a formation of fresh-water origin, 
made up in the main of sands and clays in many altera- 
tions. In places the clays occur in deposits of sufficient 
size and of such a degree of purity as to make them of 
commercial value. 

2, the Eutaw, which is of marine origin and composed 
of sands and clays more or less calcareous, but nowhere 
showing beds of limestone properly so called. 

3, the Selma chalk, which is of marine origin, and is 
composed, in part at least, of the microscopic shells of 
Foraminifera. This formation, throughout the western 
part of the belt covered by it in Alabama, is about 1,000 
feet in thickness, and is made up of beds of chalky and 
more or less argillaceous limestone. In a general way it 



may be said that the lower and upper thirds of the forma- 
tion contain 25 per cent, and upward of clayey matters 
mixed with the calcareous material, while the middle third 
will hold less than 25 per cent, oif these clayey impurities. 
4, the Ripley. This, like the preceding, is a marine for- 
mation, in which, generally, the calcareous constituents 
predominate, but in places it contains sandy and clayey 
beds. 

From this summary it will be seen that the Selma chalk is 
the one of Cretaceous formations in Alabama which offers 
limestone in such quantity and of such composition as to be fit 
for Portland cement material. 

General description. As has been stated above, the Selma 
chalk is a calcareous formation throughout its entire thickness 
of about 1,000 feet. The rock, however, varies in composition 
between somewhat wide limits, and taking account of the com- 
position we may readily distinguish three divisions of it. The 
rock of the upper or Portland division, is highly argillaceous, 
holding from 25 per cent, and upward of clayey matters ; por- 
tions of it are composed of calcareous clays or marls rather than 
limestone, and in these beds are found great numbers of fossils, 
mainly oysters. Along Tombigbee River these beds make the 
bluffs from Pace's Landing down nearly to Moscow, and on the 
Alabama they form the banks of the river from Elm Bluff down 
to Old Lexington Landing. The strata, as exhibited in these 
bluffs, consist of dark-colored, fossiliferous, calcareous clays, al- 
ternating with lighter-colored and somewhat more indurated 
ledges of purer, less argillaceous rock. At Elm Bluff, which is 
about 125 feet high, the upper half of the bluff is of this char- 
acter. The lower half of the bluff is composed of rock more 
uniform in composition and freer from clay, and is the top of 
the middle part of the Selma formation (the Demopolis divi- 
sion), which is made up of limestone of more uniform character, 
containing, generally, less than 25 per cent, of clayey material. 

In this middle or Demopolis division of the Selma formation 
the fossils are rarer than in either of the others, oysters and 
anomias being the most common forms. This variety of the 
rock forms the bluffs along Alabama River from Elm Bluff up 
to King's Landing. It is seen in its most typical exposure at 
White Bluff, where it is at least 200 feet in thickness, and 



78 

makes on the right bank of the river an almost perpendicular 
bluff. On Tcmbigbee River it extends from near Barton's 
Bluff past Demopolis up to Arcola and Hatch's Bluff. Its 
lowermost beds, a compact limestone of great purity, form the 
upper parts of Barton's and Hatch's Bluffs. On Little Tom- 
bigbee River the same rock makes the celebrated bluffs at 
Bluffport and at Jones Bluff (Epes), beyond which for several 
miles it is shown along the stream. 

Judging from the width of its outcrop, this division of the 
Rotten limestone must be about 300 feet in thickness. It 
underlies the most fertile and typical "prairie" lands of the 
South. At intervals throughout this region the limestone 
rock appears at the surface in what are known as "bald prair- 
ies," so named from the circumstance that on these spots there 
is no tree growth. The disintegration and leaching cut of the 
limestone leaves a residue of yellowish clay, which accumulates 
sometimes to a thickness of several feet in low places. This 
clay is used at the Demopolis plant in the manufacture of ce- 
ment, and in> most localities where suitable limestone is found 
the clay is present in sufficient quantity to supply the needs of 
the cement manufacturer. 

At the base of this middle or Demopolis division occurs a 
bed consisting of several ledges of compact, hard, pure lime- 
stone, which weathers into curious shapes, and has received 
the names horse-bone rock and bored rock. This bed, as above 
mentioned, appears at the top of Hatch's Bluff ; also at Arcola 
Bluff, and between Demopolis and! Epes, at Jordan's Ferry, and 
other places. Where it outcrops across the country it makes 
a ridge easily followed and characterized by the presence on 
the surface of loose fragments of the limestone. 

The lower part of the formation (the Selma division), like 
the upper, is composed of clayey limestone, in many places be- 
ing rather a calcareous clay. The color is dark gray to bluish, 
and in most exposures there is a striping due to bands of light- 
colored, purer limestone alternating with the prevailing quality. 
Along Alabama River the strata of this division are seen in 
the bluffs from King's Landing up to Selmai and beyond. On 
the Warrior River they are seen in the bluffs at Arcola, Hatch's, 
Millwood, and Erie, occupying in the last-named locality the 
upper part only of the bluff. On the Tombigbee, the bluffs at 
Gainesville, at Roe's, and Kirkpatrick's are formed mainly of 



79 

the rocks of this division, while above Roe's, at Jordan's, occurs 
the line of junction of this with the middle division. Near this 
line of division there is a very characteristic feature to be ob- 
served at many points, viz., about 10 or 15 feet below the hard 
lulges cf pure limestone forming the base of the middle 
(Demcpolis) division the dark-colored argillaceous rock shows 
a tendency to flake oft" and weather into caves, sometimes to be 
seen for long distances along the bluffs, as on Alabama River 
just above King's Landing, on the Tombigbee below Roe's 
Bluff, and at Jordan's Ferry. This peculiarity is illustrated in 
Plate IT. The outcrop of the argillaceous rocks of this division 
gives rise to black prairie soils, in which beds of fossil shells, 
mainly oysters, are common. 

It has been suggested that the: argillaceous rocks of this and 
the uppermost division could be mixed with the purer limestone 
of the middle division in such proportions as to constitute a 
good cement mixture. In this case it would be easy to select 
localities near the junction of the two divisions where both va- 
rieties of the rock could be quarried, if not in the same pits, at 
least in pits closely adjacent. This would do away with the 
need of adding other clay to the limestone. Localities of this 
sort would be found along the border north and south of the 
belt of outcrop of the white Demopolis rock. 

Details of localities. The general characters of the rock of 
this formation have been mentioned above, and it remains to 
give details of the special localities examined, together with 
analyses of the limestones collected. In making the collections 
material from the middle or Demopolis division of the forma- 
tion has been generally chosen, since most of the limestone of 
the formation which contains 75 per cent, and upward of car- 
bonate of lime is to be found in this division. At the same time 
specimens of the more argillaceous material, especially O'f the 
lower (Selma) division of the formation, have been taken for 
comparison and analysis, with a view to ascertaining whether 
or not it will be practicable to provide a cement mixture by 
using the proper proportions of the purer and 1 more argillace- 
ous materials. 

Inasmuch as suitable material for cement manufacture can be 
had in practically unlimited quantity all along the outcrop of the 
pure limestone of the Demopolis division, the location: of the 
plants for the manufacture of this product will be determined bv 



80 

ether considerations than the quality of the rock. Chief among 
these will be the facilities for transportation, cheapness of fuel, 
cost of labor and abundance of it at command. 

Examinations have consequently been confined to those lo- 
calities which appear to be most favorably situated in these re- 
spects, and especially to those localities which are on navigable 
streams or on north-south railroad lines, or on both. 

The first place considered on Tombigbee River is Gainesville, 
where the limestone appears on the river bluff in a thickness of 
30 to 40 feet, beneath a heavy covering of Lafayette sands and 
pebbles. (Plate III.) A short distance inland from the river, 
how r ever, the rock appears at the surface, and may be quarried 
without difficulty. Specimens have been taken from the differ- 
ent parts of the bluff near the ferry, which will show the com- 
position of the limestone here (see analyses i, 2, 3, and 4, Table 
E). Other specimens are from the Roberts place, 3 miles easi 
of Gainesville one of which was taken from the top of a 30- 
foot bluff ; others from the surface I mile and 5 miles from the 
river (analyses 5 and 6.) 

At Jones' Bluff, on the Tombigbee, near Epes station, on the 
Alabama Great Southern Railroad, the white limestone of re- 
markably uniform composition shows along the river bank for 
a distance of a mile or so, with an average height of perhaps 60 
feet. (Plate IV.) Here the bare rock forms the surface, so 
that there would be no overburden to be removed in quarrying. 
The railroad crosses the river at this locality, which thus has the 
advantage of both rail and water transportation. From the 
lower end of this exposure down to Bluffport the white rock is 
seen at many points, e. g., below Lees Island, Hillman's (Plate 
V), Martin's Ferry, Braggs, etc. It generally has a capping 
of 15 to 20 feet of red loam and other loose materials. 

Specimens have been analyzed from Epes and Hillman? 
(analyses 7, 8 and 9, Table E.) 

At Bluffport (Plate VI) the white rock in places forms a 
bluff 100 feet or more in height along the right bank of the 
river for a distance of a mile or more. This is the counterpart 
of Jones' bluff, above mentioned, and the character of the ma- 
terial is shown by analysis No. 10. As at Epes. the rock ex- 
tends up to the surface, so that the quarrying would be attended 
with little or no difficulty. Below the Bluffport bluffs the east- 
erly course of the river brings it into the territory of the lower 



or THE 

UNIVERSITY 

or 




or THE. 

IR 

or 




or THE 

( UNIVERSITY ) 




Plate XII. Alabama Fo 






nd Cement Works, at Demopolis. 



81 

strata of the formation, and we do not see the white rock again 
below Jordan's Ferry, (Plate VII) except in thin patches at 
tops of some of the bluffs. The character of the material of 
these lower beds may be seen from the analyses of specimens 
taken from Jordans and Belmont and Roe's bluff, Nos. n, 12, 
13, and 14. The two specimens from the last-named locality 
represent the composition of the prevailing dark-colored! argil- 
laceous rock and of the lighter-colored ledges. (Plate VIII.) 

At Demopolis there is an important occurrence of the white 
rock extending along the left bank from a mile above the land- 
ing to about 2 miles below, with an average height perhaps of 
40 or 50 feet. (Plates IX and X.) The rock is remarkably 
uniform in appearance and probably in composition (analysis 
17.) At McDowell's the main bluff is on the right bank and 
the rock is of great purity, as shown by analysis 16. The ex- 
posures continue down to Pace's Landing, 9 miles below De- 
mopolis, and beyond this the bluffs are much darker in color 
and striped with lighter bands, characteristic of the strata of the 
upper part of the formation. Thence down nearly to Moscow 
occur the exposures of these upper beds. 

Above Demopolis at Arcola and Hatch's bluff the bluish 
clayey limestones of the Selma division are seeni in force, with 
the lowermost ledges of the Demopolis division the horse- 
bone rock capping them. Two analyses of these varieties at 
Hatches will show well the contrast in their chemical composi- 
tion (analyses 19 and 20. (Plate XI.) 

From Demopolis eastward the line of the Southern Railway 
is located on the outcrop of this white rock, at least as far as 
Massillon, where it passes into the territory of the lower Selma 
division. Two miles from Demopolis on this road is the cement 
manufacturing plant of the Alabama Portland Cement Com- 
pany, with six kilns in place. The quarry is on the opposite 
side of the railroad track from the kilns, but only a. few hundred 
feet distant. (This plant with quarry in the foreground is 
shown in Plate XII.) The clay used is the residual clay from 
the decomposition of the limestone, and is obtained from the 
river bank a few yardls away. The composition of the rock and 
of the clav used in the manufacture is shown by analyses 15, 18, 
and 31, Table E, and I, Table G. A specimen taken from Knox 
wood station, between the cement works and Demopolis station, 
shows similar composition. The analyses below given (10, n, 
6 



82 

12 of. Table G) show the chemical character of the cement man- 
ufactured at Demopolis. 

At Van Dorn station the white rock outcrops in the fields 
over considerable territory, (Plate XIII), and just east of the 
station there is a deep cut through it. Analyses from about 
Van Dorn show sufficiently well the character of the material 
at these points (analyses 21 and 22 of Table E.) 

About Uniontown the bare rock is exposed at numerous 
points, and the advantages of this place for the location of man- 
ufacturing plants seem to be very great. Specimens have been 
taken from the Bradfield and Shields places, west of the town, 
and from the Pitts place east, and from a point south of the 
town along the McKinley road. Other specimens have come 
from plantations near the road for several miles eastward! and 
the analyses are appended (analyses 23, 24, 25, 26, 27 and ~ 

The composition of the res^aual clay overlying the limestone 
at the Pitts place is shown in analysis No. 2 of Table G, and 
that of a similar clay from the "Graveyard Hill" on the Mor- 
gan place, by analysis No. 3 of same table. 

South of Massillon, near the crossing of the Southern and 
Louisville and Nashville railroads, in the vicinity of Martin's 
station, the white rock showis in numerous exposures through 
the fields, making a country somewhat similar to that about 
Unicntown. At many points the rock has no overburden, and 
is admirably adapted to cheap quarrying. On the banks of 
Rogue Chitto Creek, near Martin's station, on the Milhous 
place, the rock is exposed in a bluff with a bed of plastic clay 
overlying, but here it is below a considerable thickness of red 
loam and sandis of the Lafayette formation. The character of 
the rock at Milhous station, west of Martin's, may be seen 
from the analysis No. 29, Table E. 

The same rocks make the great bluff of White Bluff, on Ala- 
bama River, (Plate XIV.) Specimens were selected from 
this bluff at two points one about halfway down the bluff, the 
other twenty feet lower. Generally there is a capping of the 
red loam and sands of the Lafayette over the limestone, but 
near the upper end of the bluff the white rock extends to the 
summit, where it has a capping of plastic clay only. The char- 
aster of the limestone from this locality is s'hown in analysis 30, 
Table E, and that of the overlying residual clay in analysis 4 of 
Table G. 

At Elm Bluff, as has already been shown, the upper and 
middle divisions of the formation are in contact. (Plate XV.) 



83 

At King's Bluff the middle and lower parts of the formation 
are in contact. At the other bluffs of the river between King's 
Landing and Selma the rock of the lower division is exhibited). 
No. 32 (Table E) is of the rock at the steamboat landing in 
Selma ; No. 33 of rock occurring near Selma ; No. 34 from Ca- 
haba ; and No. 35 from Benton. 

These analyses show that the rock of this division is in gen- 
eral too clayey for the best cement rock, but it might be mixed 
with the purer limestone of Unicntown, or Demopolis in mak- 
ing up a cement mixture. 

To summarize : From Demopolis eastward along the line 
of the Southern Railway, by Van Dorn, Gallion, Uniontown, 
Massillon, and thence by Martins and Milhous stations to White 
Bluff, the white or Demopolis type of reck appears at the sur- 
face in clean exposures at almost innumerable points, either 
immediately on the railroad or at very short distance from it. 
So far as the quality, quantity, and accessibility of the lime- 
stone rock are concerned, -manufactories cf cement might be 
located almost anywhere in this territory. From Demopolis 
westward the same conditions prevail up the river to Epes, and 
thence to Gainesville, beyond which point the white rock is to 
the west cf the river at greater or less distance. 

East of Alabama River the outcrop of the cement rock is 
crossed by the Louisville and Nashville Railroad (Repton 
branch), as before stated, between Berlin and Pleasant Hill 
stations. At Benton, on Alabama River, and on the railroad, 
the limestone has the composition shown by analysis 35. 

On the Montgomery and Selma road, at the crossing of Pint- 
lala Creek near Manack station, the limestone is exposed in the 
creek banks and in the open fields, often with little or no over- 
burden. In Table E are given analyses of a specimen from the 
fields along the wagon road (No. 36), and from the creek bank 
(No. 37.) 

On the main branch of the Louisville and Nashville Railroad 
the white rock shows between the city and McGhees switch, and 
an analysis of a specimen from McGhees is given (No. 38.) 
Somewhat similar, but ratber better, is the limestone from H. 
A. Jones, 8 miles south of Montgomery, shown in analysis 
No. 39. 

Examinations have not been carried beyond Montgomery, 
but it is known that the white prairie rock is crossed bv the 
Central of Georgia Railroad between Matthews and: Fitzpatrick 
stations, and there seems to be no doubt that along this stretch 
of the road suitable rock will be found convenient to the line. 



84 



Table E. 
Analyses of Crateceous Limestones. 



,,, 


55 


Iron and alumi- 
num oxides. 


Calcium 
carbonate. 


Magnesium 
carbonate. 


Sulphuric 
anhydride. 


Total sulphur. 


o 

if 


1 Gainesville Bluff, Tombigbee river, 
5 feet from top of bluff; R. S. 
Hodges, analyst 
2 Gainesville Biuff, Tombigbee river, 
lower part of bluff; R. H. Hodges, 
analyst ... 


18.46 
14 50 


16.04 
11 64 


56.71 

67 67 


1.69 
2 26 


1.32 
1 97 





5.78 
1 96 


3 Gainesville limestone; F. P. Dew- 
ey, analyst 
4 Gainesville limestone; A. W. Dow, 
analyst 


18.42 
27 25 


10.79 
15 96 


65.21 
54 00 


1.57 

11 11 
J..J..L 


.30 
44 


0.83 
1 23 




5 Robert's place, near Gainesville, top 
of bluff; R. S. Hodges 
6 Robert's place near Gainesville, 5 
feet above water; R. S. Hodges.. 
7 Jones Bluff, at Epes; R. S. Hodges 



12.10' 

14.28 
4 78 


10.70 

11.80 
6 42 


75.57 

69.75 

86 28 


1.24 

1.50 
1 02 


.69 
1.02 




1.70 

1.65 
1.30 


S Jones Bluff, at Epes; Dr. Mallett.. 
9 Hillmans Bluff, below Epes; R. S. 
Hodges 
10 Bluff port ferry, Tombigbee river; 
R. S. Hodges 


3.23 
10.08 
8 10 


3.96 
9.47 
5 40 


80.48 
77.43 
85 10 


.53 
1.30 

11 25 
- 1 ' 







2.22 
1.99 


11 Jordans ferry, Tombigbee river; 
R. S. Hodges ... 






67 28 


1 87 






1 53 


12 Belmont Bluff, Tombigbee river; 
R S Hodges 


21 00 


15 60 


55 84 


2 12 






5 44 


13 Roes Bluff, Tombigbee river, main 
part of bluff; R. S. Hodges 


20 40 


1576 


55 82 


2 10 






5.92 


14 Roes Bluff, Tombigbee river, light- 
colored ledges; R. S. Hodges 
IP Demopolis limestone, F. P. Dew- 
ey; U. S. Mint, analyst 


9.68 
13 32 


8.70 
7 74 


78.52 
73 94 


1.02 
1.40 


.27 


.64 


2.08 


16 McDowells Bluff, below Demo- 
polis; R. S. Hodges 


3 82 


3 86 


90 40 


11 15 






77 


17 Demopolis limestone; Dr. J. W. 
Mallett, analyst 
18 Material used in Demopolis Ce- 
men Wks; R. S. Hodges, analyst. 
19 Hatch's Bluff, Warrior river above 
Demopolis; main part of bluff; 
R. S. Hodges 
20 Hatch's Bluff, Warrior river above 
Demopolis; ledges at top of bluff; 
R. S. Hodges 


12.13 
7.64 

25.90 
1.78 


7.45 
7.62 

19.44 
2.34 


77.69 
80.71 

44.78 
93.52 


.72 
1.05 

2.68 
1.38 


1.62 





2.49 
1.36 

7.20 
.98 



85 



Analyses of Crateceous Limestones. Continued. 



Locality. 


Silica. 


Iron and alumi- 
num oxides. 


Calcium 
carbonate. 


Magnesium 
carbonate. 


Sulphuric 
anhydride. 


Total sulphur. 


! 

?! 

% ' 

gi 


LM At VanDorn station, from road- 
side; R. S. Hodges 


8 90 


8 26 


80 47 


11 30 






1 07 


22 At VanDorn station, railroad cut 
east of station; R. S. Hodges 


9.80 


7.85 


78.77 


i.OU 

1.04 






2.54 


23 Uniontown, P. H. Pitt's Home 
place; R. S. Hodges 


10.86 


8.40 


75 35 


1 35 






4 04 


24 Uniontown, P. H. Pitts, Houston 
place; R. S. Hodges 


13 58 


9 20 


72 21 


1 98 






3 03 


25 Uniontown, P. H. Pitts, Rural Hill 
place; R. S. Hodges 
2o Uniontown, 1 mile south on Mc- 
Kinlev road; R. S. Hodges 


12.10 
7.56 


9.80 
17.18 


74.52 
83.45 


1.17 
1 53 






2.41 


27 Uniontown, Bradfield place; R. S. 
Hodges 


17 77 


9 24 


65 96 


Ik52 






5 51 


2o Uniontown, Shields place; R. S. 
Hodges 


19 62 


11 71 


62 81 


2 04 






2 49 


29 R. R. cut, Milhous station, So. Ry. 
Dallas county; R. S. Hodges 
30 White Bluff, Alabama river, lower 
part of bluff; R. S. Hodges 


10.50 
17.44 


7.24 
11.48 


80.10 
64 35 


.98 
1 61 






1.18 
5.29 


31 Limestone used in. cement works. 
Demopoli.^; analysis furnished by 
T G Cairns 


9 88 


6 20 


77 12 


1 08 






5 72 


32 Limestone from bluff at steamboat 
landing, Selma; F. W. Miller, 
analyst 


16 11 


11 " 


65 08 


2 42 


1 40 




3 37 


33 Near Selma, white rock; O. M. 
Cawthon R S Hodges 


18 66 


13 42 


64 10 


o 5g 


08 




1 16 


34 Limestone from Cahaba, Alabama 
river; Dr. Mallet 


19 64 


9 40 


65 81 


79 






3 58 


3=) Limestone from Benton, Alabama 
river' Dr W B Phillips 


19 74 


11 67 


54 83 


5 14 


85 




4 96 


3T Limestone from Manack station, 
Lowndes county; R. S. Hodges... 
3'. 7 Limestone, Manack station; Dr. B. 
B Ross analyst . ... 


13.50 
13 20 


11.46 
9 00 


67.16 

74 26 


1.08 
1 46 


1.01 





5.79 


38 Limestone, McGhee's Switch, 
Montgomery co.; R. S. Hodges... 
39 Limestone, H. A. Jones, 8 miles S. 
of Montgomery; R. S. Hodges 


21.98 
14.90 


14.78 

i 
14 34 


54.67 
63.28 


1.39 
1.47 


.11 





7.07 
6.01 



















86 



THE ST. STEPHENS LIMESTONE. 

General Description. The St. Stephens or White limestone 
formation of the Alabama Tertiary, which includes the upper- 
most of the Eocene strata, is in general equivalent to the Vicks- 
btirg limestone of the Mississippi geologists. 

In Alabama it exhibits three rather well-defined phases, 
which in descending order are ( I ) the Upper or Salt Motmtain 
division, observed at one locality only in Clarke county; (2) 
the Middle or St. Stephens division, and (3) the .Lower or 
Jackson division. Of these it is only the middle division with 
which we are here concerned, since the first is, so far as known, 
restricted to one locality, and the third is seldom exposed along 
Alabama rivers and railroads. 

The following section of the St. Stephens Bluff, Tombigbee 
River, (Plate VI), will give an idea of the strata of this di- 
vision : 

Section of St. Stephens Bluff. 

FEET. 

1. Red residual clay 1 to 5 

2. Highly fossiliferous limestone holding mainly oysters, 

and full of holes, due to unequal weathering 10 to 12 

3. Orbitoidal limestone (chimney rock), a soft, nearly uni- 

form porous limestone, making smooth perpendicular 
face of the bluff except where bands of harder lime- 
stone of very nearly similar composition alternate with 
the softer rock. Both varieties hold great numbers of 
the circular shells of Orbitoides mantelli. These harder 
ledges are nearly pure carbonate of lime, take a good 
polish, and are often burned for lime 60 

4. Immediately below 3, for 5 or 6 feet, the strata were not 

visible, being hidden by the rock falling from above, 
but the space seems to be occupied by a bluish clay. 
Then follows a soft rock somewhat of same consistency 
as No. 3 above, but containing a good deal of green 
sand. The fossils are mostly oysters and P/m//oxf<mm 
dumosa. This bed is in places rather indurated super- 
ficially, and forms projecting ledges 10 to 15 



87 

5. Bluish clayey marl with much green sand, containing the 

same fossils as No. 4. It washes or caves out from 

under No. 4, which overhangs it 4 to 5 

6. Massive joint clay, yellow on exposed surface, blue when 

freshly broken; no fossils observed. Extends below the 

water level to unknown depth; exposed 3 to 4 

The rock of this formation, which seems to be the best suited 
for cement material, is the soft "chimney rock" or orbitoidal 
limestone of bed No. 3 above. This usually quarried for chim- 
neys and other constructions by sawing it out and dressing it 
doAvn with a plane into blocks of suitable size, which are then 
laid like brick. 

The numerous analyses given below will show that this rock 
is a purer limestone than most of the material of the Selma 
chalk of the Cretaceous formation above considered. In ce- 
ment making it will, in consequence, require a larger proportion 
of clay to be mixed with it, and! the question of obtaining suit- 
able clay in sufficient quantity and in close proximity becomes 
one of some importance. The residual clay left after decompo- 
sition and leaching of the limestone seems to be fairly well 
adapted to the purpose. Besides this residual clay some analy- 
ses have been made of the clays of thie river and creek bottoms 
of the country near the limestone outcrops, and of the clays of 
the Grand Gulf formation, which very generally in this section 
overlies the limestone. Some analyses of the last named clays 
have been made from material occurring near St. Stephens, and 
near Manistee Junction en the Repton Branch of the Louisville 
and Nashville Railroad. At this last-named locality the clay 
is present in sufficient quantity to be oi value if the composition 
is suitable. 

Details of Localities. 

St. Stephens. The first locality to be considered is the bluff 
at St. Stephens, a section of which has been given, andl it may 
be taken as a typical section of the formation everywhere. At 
St. Stephens the whole of the soft orbitiordal limestone or 
"chimney rock" might be used, as the composition is uniform 
throughout. The overlying harder limestone has almost the 
same composition, but it is less easily crushed and handled. It 
may be quarried here from the surface down, as it is covered 
only by a thin layer of residual clay. The characters of the 
limestone and of the clay from here are sufficiently well shown 



88 

by the subjoined analyses (No. i of Table F, and 5 and 6, Table 
G.) The character of the clay of Grand Gulf formation near 
St. Stephens is shown in analysis No. 8 of Table G. 

Below St. Stephens there is deep water to Mobile, with the 
exception of one bar, which may be removed without much 
trouble or expense. 

Oven Bluff. Frcrn Hobson's quarry, just above the Lower 
Salt Works Landing-, down to Oven Bluff, a distance of 2 
miles, the orbitoid&l limestone or chimney rock occurs at the 
base of bluffs of Tertiary age. 

At the quarry the hard limestone, which is being taken up 
for riprap work, lies ,as at St. Stephens, just above the soft 
chimney rock. Along the stretch of river above described this 
chimney rock is seen in a bed 15 to 20 feet in thickness, just 
above the river bottom, and is easily accessible. Analysis 2, 
Table F, of a, sample from Oven Bluff will show the quality 
of the limestone here. As regards clay three varieties have 
been examined, a residual clay from over the limestone, a 
swamp-bottom clay from the low grounds of Leatherwood 
Leatherwood Creek, and clay from strata of the Grand Gulf 
formation which here overlies the St. Stephens limestone. The 
analyses of these clays have not yet been made. 

The first shoal in the river abov/e, Mobile is a few miles above 
Oven Bluff, so that from this place down there is a Q-foot chan- 
nel at all seasons, which will give to Oven Bluff a certain ad- 
vantage over other localities in regard to transportation. The 
shoal mentioned is one which can be removed, so that St. Ste- 
phens may be classed with Oven Bluff as regards transportation 
by water, except that the former is some miles farther from the 
Gulf than the latter. 

Analyses by Dr. Mallett of other specimens of this chimney 
rock are here presented!. No. 8, Table F, is of a specimen from 
Colonel Darrington's place, in the lower part of Clarke county 
near Gainestown, and 9 and 10 are from other localities in 
Clarke county near the rivers. 

Localities along the line of the Southern Railway. At Glen- 
don station, a few miles east of Jackson, there is an exposure of 
the chimney rock close to the track. The rock here is about 
20 feet thick, and the limestone is covered by a bed of red re- 
sidual clay similar to that at St. Stephens and Oven Bluff. The 
same chimney rock may be seen along the road between the sta- 



89 

tion and Jackson, and no doubt it occurs from Glendon up to 
Suggsville station, within convenient reach of the railroad. At 
Suggsville station the same rock occurs along the road leading 
from station to the town. This place is within a short distance 
of the railroad. 

Between Suggsville and Gosport, the country rock is the St. 
Stephens limestone, but no particular attention was given to it 
for the reason that no railroad crosses the county along this 
line. 

Along Alabama River. At Perdtue Hill the St. Stephens 
rock outcrops near the base of the hills which descend to the 
terrace on which the town of Claiborne stands. The bluff at 
Caliborne Landing shows near the summit the calcareous clay 
or clayey limestone which lies at the base of the St. Stephens 
formation, and which is generally thought to be the equivalent 
of the Jackson group of the Mississippi geologists. It is quite 
possible that this rock, where it occurs in sufficient quantity, 
may be suitable for cement making,, since it has a composition 
not far different from much of the Rotten limestone or Selma 
chalk. No investigations have yet been made concerning it, 
for the reason that there are comparatively few points where it 
appears in adequate thickness and in favorable localities as re- 
gards transportation. 

At Marshall's Landing, just above the mouth of Randon's 
Creek, is the first exposure of the chimney rock along Alabama 
River. This occurs at the top of the bluff. It has the usual 
covering of residual clay, and the analyses presented (3 of Table 
F, and 7 of Table G,) will show the composition of the two. 
Below the orbitoidal or chimney rock at Marshall's there are 
20 feet or more of a porous limestone, the analysis of which is 
given in Table F, No. 4. In the same bluff there are beds of 
calcareous clay which might possibly be used in mixing with 
the limestone. At the landing these wouia be difficult to quarry 
because of overlying strata, but they would certainly be found 
without cover along the bluffs above Marshall's if they should 
prove of value. 

From Marshall's down to Gainestown Landing the river 
bluffs show beds of the limestone at numerous points. At 
Gainestown, the topmost bed of the St. Stephens, the hard crys- 
talline limestone occurs not far above the water level in the 
river. This stone has been cut and polished and proves to be 



90 

a first-rate marble, inasmuch as it takes a good polish and shows 
agreeable variations in color. The soft chimney rock underlies 
the hard limestone here as at other points. 

At Choctaw Bluff, some miles below Gainestown, there is the 
last exposure of the Tertiary limestones on the river. The ma- 
terial is an argillaceous limestone with numerous fossils, but it 
seems hardly likely to be of use in cement making. 

Between Alabama River and the main line of the Louisville 
and Nashville Railroad. A few miles east of Marshall's Land- 
ing, at Manistee Mills, the terminus of a sawmill road, there is 
a quarry of the chimney rock, conveniently situated as to trans- 
portation, since it is on the railroad. Across the country to the 
Repton Branch of the Louisville and Nashville Railroad, the 
St. Stephens limestone may, of course, be found at thousands 
of places, but no mention is made of these occurrences where 
thtey do not lie on railroad line. 

Below/ Monroe Station, near Drewry on the Repton Branch, 
this road crosses the line of outcrop of the chimney rock, which 
at a number of points in the vicinity- of Drewry lies within 
easy reach of transportation. 

A few miles below Drewry, at Manistee Junction, there is a 
fine exposure of Grand Gulf clays in railroad cuts, both north 
and south of the station. 

Analysis is given (No. 9 of Table G), of the clays from these 
cuts, from which their suitability from admixture with the 
limestone may be determined. 

On the mam line of the Louisville and Nashville Railroad 
The chimney rock may be found at many points below Ever- 
green in the vicinity of Sparta and Castleberry stations. There 
are many bluffs of this rock on the banks of Murder Creek in 
this vicinity, and there are several quarries from which the stone 
has been obtained for building purposes, within short distance 
of the railroad line. At the foot of Taliaferro's Heights the 
limestone forms high bluffs om the creek; at Ellis Williams 
Spring there are bluffs with the soft rock at the base and the 
hard horse-bone rock at the top, and on the creek bank, a few 
hundred yards away, is one of the quarries mentioned above. 
In fact the localities where the rock may be found within con- 
venient distance of the railroad, and in a position favorable to 



91 

cheap quarrying, are numerous in all this region. No clays 
were seen except the usual residual clays from the decomposi- 
tion of the limestone and a clay occurring close to Evergreen in 
the pits of Wild Brothers. Analyses 5, 6 and 7 of Table F, 
will show sufficiently well the character of the limestone in this 
section. 

The Evergreen occurrences have attracted attention because 
of their location on the line of a great railroad system within 
short distance, of tide water. 

Farther to the east this limestone formation extends across 
Alabama and into Georgia and Florida, but as there is no north- 
south railroad east of the Louisville and Nashville at this time, 
the investigations have gone no further. 

To summarize : While the St. Stephens limestone outcrops 
across the State from the Mississippi line to the Chattahoochee 
River, often occupying broad belts, attention has been concen- 
trated on those localities which lie upon navigable streams or 
upon railroad lines terminating in Gulf ports. As compared 
with the Demopolis division of the Selma chalk, this limestone 
is more uniform in composition, higher in lime content, softer 
and more easily quarried and crushed, and in geographical posi- 
tion many miles nearer the Gulf. 

Its thickness, on the other hand, is much less, although suffi- 
cient to supply an indefinite number of manufactories with raw 
material for cement. 




92 



Table F. 
Analyses of Tertiary Limestones. 



Locality. 


Silica. 


Iron and alumi- 
num oxides. 


Calcium 
carbonate. 


Magnesium 
carbonate. 


Sulphuric 
Htlhydride. 


Water and or- 
ganic matter. 


1 St. Stephens orbitoidal limestone, 
St. Stephens, Tombigbee river; R. 
S. Hodges, analyst 
2 Orbitoidal limestone, "Chimney 
Rock," Oven Bluff, Tombigbee 
river ; R. S. Hodges 


2.28 
4 18 


2.04 
3 26 


92.85 
89 32 


1.92 
2 38 


.13 

15 


81 


3 Orbitoidal limestone, Marshall's 
Landing, Alabama river, Monroe 
county R S Hodges ... 


2 52 


1 50 


94 07 


1 90 


08 




4 Limestone underlying the orbi- 
toidal rock, Marshall's Landing; 
R S Hodges 


11 44 


3 34 


80 46 


3 09 


15 


1 52 


5 Chimney Rock, Taliaferro's 
Heights, near Evergreen, Cone- 
cuh county R S Hodges 


2 84 


2 16 


91 31 


1 83 


07 


1 79 


6 St. Stephens orbitoidal limestone, 
near Evergreen; Dr. W. B. Phil- 
lips analyst 


1.26 


1.72 


96 09 


65 


02 


65 


7 Orbitoidal limestone near Ever- 
green- D W B Phillips 


2 75 


2 73 


93 31 


23 


02 


60 


8 St. Stephens orbitoidal limestone, 
Col. Darrington's, near Oven 
Bluff Clarke co- Dr. J. W. Mallet 


1.69 


2.12 


94.84 


96 






9 St. Stephens orbitoidal limestone, 
Clarke co. near river; Dr. J. W. 
Mallet analyst 


2 44 


27 


94 85 








10 St. Stephens orbitoidal limestone, | 
Clarke county near river; Dr. J. W. 


4.15 


1.29 


93.19 


1.09 





















93 



Table G. 
Analyses of Clays (Cretaceous and Tertiary) and Cement. 



Number ot 
anaylsis. 


1 

53 


Iron and alumi- 
num oxides. 


Calcium 
oxide. 


Magnesium 
oxide. 

C",,l^U,,~4~ 


anhydride. 


Total sulphur. 


Ignition. 


\ Residual clay over limestone, at 
















Demopolis Cement Works; R. S. 
















Hodges analyst 


55.64 


26.25 


.91 


1.97 


Tr 




13.90 


2 Residual clay over limestone at P. 
















H. Pitts' Home Place, Uniontown; 
















T> g HodsrGS 


69.57 


19.04 


37 








9.68 


3 Residual clay, Graveyard Hill, 
















Morgan Place, Uniontown; R. S. 
















Hodges 


56.74 


28.10 


.70 


1.27 


Tr 




13.80 


4 Residual clay, Reid Place, White 
















Bluff, Alabama river, Dallas co. ; 
















R. S. Hodges 


56.90 


27.71 


.86 


1.64 


.09 


.... 


11.26 


5 Residual clay over orbitoidal lime- 
















stone, St. Stephens, Washington 
















county; R. S. Hodges 


59.71 


24.79 


.37 






.... 


14.96 


G Residual clay over limestone, St. 
















Stephens Bluff; R. S. Hodges 


44.94 


36.36 


5.14 


1.20 






13.77 


7 Residual clay over limestone at 
















Marshall's Landing, Alabama 
















river, Monroe county; F. W. 
















Miller analyst 


51.30 


33.22 


1.37 


.96 


.41 




9.42 


8 Grand Gulf clay, west of St. Steph- 
















ens, Washington co. ; R. S. Hodges 


60.68 


25.60 


.48 


.38 


Tr. 


.... 


9.92 


9 Grand Gulf clay, Manistee June., 
















Monroe county; F. W. Miller, 
















analyst 


66.60 


25.86 


.34 


.34 


.89 




5.11 


10 Cement manufactured by Alabama 
















Portland Cement Co., Demop- 
















polis; A. W. Dow, U. S. inspector 
















of asphalts and cements, analyst. 


| 20.25 


13.44 


63.60 


1.03 


.41 


0.99 




11 Cement manufactured by Alabama 


I 














Portland Cement Co., Demo- 


| 














polis; analysis from T. G. Cairns, 


! 














general manager 


19.99 


13.74 


61.36 


.61 









12 Cement manufactured by Alabama 


! 














Portland Cement Co., Demo- 


! 














polif; R S. Hodges, analyst 


| 19.99 


13.63 


63.82 


.83 


1.16 








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