Voids, settlement and weight of crushed stone

135
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UNIVERSITY OF ILLINOIS BULLETIN

Vol. V.

MAY 6, 1908

No. 23

[Entered Feb. 14, 1902, at Urbana, 111., as second-class matter under Act of Congress

July 18, 1894]

BULLETIN NO. 23

VOIDS, SETTLEMENT AND WEIGHT OF
CRUSHED STONE

BY

IRA O. BAKER

UNIVERSITY OF ILLINOIS
ENGINEERING EXPERIMENT STATION

URBANA, ILLINOIS

PUBLISHED BY THE UNIVERSITY

HE Engineering Experiment Station was established by
action of the Board of Trustees December 8, 1903. It is
the purpose of the Station to carry on investigations
along various lines of engineering and to study problems
of importance to professional engineers and to the manu-
facturing, railway, mining, constructional, and industrial interests
of the state.

The control of the Engineering Experiment Station is vested
in the heads of the several departments of the College of En-
gineering. These constitute the Station Staff, and with the Di-
rector, determine the character of the investigations to be under-
taken. The work is carried on under the supervision of the Staff;
sometimes by a research fellow as graduate work, sometimes by
a member of the instructional force of the College of Engineer-
ing, but more frequently by an investigator belonging to the.
Station corps.

The results of these investigations are published in the
form of bulletins, which will record mostly the experiments of the
Station's own staff of investigators. There will also be issued
from time to time in the form of circulars, compilations giving
the results of the experiments of engineers, industrial works,
technical institutions, and governmental testing departments.

The volume and number at the top of the title page of the
cover are merely arbitrary numbers and refer to the general publi-
cations of the University of Illinois; above the title is given the
number of the Engineering Experiment Station bulletin or circular.
which should be used in referring to these publications.

For copies of bulletins, circulars or other information,
address the Engineering Experiment Station, Urbana, Illinois.

UNIVERSITY OF ILLINOIS
ENGINEERING EXPERIMENT STATION

BULLETIN No. 23 MAY 1908

VOIDS, SETTLEMENT AND WEIGHT OF
CRUSHED STONE

BY IRA O. BAKER, PROFESSOR OF CIVIL ENGINEERING

INTRODUCTION

Crushed stone has become an important material of construc-
tion in modern engineering work. The chief causes for this are
the great increase in the use of plain and reinforced concrete,
and the increased activity in macadam road construction. The
advances made in these lines have been so rapid that crushed
stone has suddenly changed from a minor material to one of first
importance in modern engineering construction. This has been
done in such a short time that the present knowledge of the prop-
erties of crushed stone is entirely inadequate; and the determin-
ation of its weight, voids, and settlement, and the variations of
these have never been attempted on any adequate scale, so far
as the writer has been able to ascertain. Before commencing this
article a diligent search was made of engineering literature for
information upon this subject. No definite information was found
concerning the weight of a cubic yard of stone of different sizes
(except one item as noted in Appendix I) or the amount of settle-
ment in transit. The only other reference on the subject was the
request of a correspondent in one of the leading engineering
journals for information regarding the weight of crushed stone.
In answer a wide range of limits was given with the explanation
that as no definite values were known, the general practice was to
assume some value within these limits.

169957

2 ILLINOIS ENGINEERING EXPERIMENT STATION

The need for reliable data on these subjects is very apparent
to the engineer who makes designs and estimates. Accustomed
to use all other materials, both of engineering and everyday life,
and to deal with standard units of weights and measures, he finds
here that there are no standards at all. For instance, practically
all of the quarries sell stone by the yard, but the so-called yard
in one place is not always the same as the yard at some other
place. In most cases a certain weight is taken as a yard; but
these weights are generally arbitrary amounts that are supposed
to approximate the true value, and they differ for different locali-
ties and for the different kinds and sizes of stone. Consequently,
the number of yards and therefore the cost of the stone for the
same piece of work would differ according to the location of the
stone supply. Furthermore, this ambiguity may cause difficulties
to arise between the producer, the carrier, and the consumer.
The producer measures the volume loose in the car after it is
loaded from the crusher. The railway then weighs the cars and
computes the number of cubic yards by assuming the weight of a
yard. The consumer receives the invoice from the producer, and
the freight bill from the railway, and tries to check them, but
generally finds they do not agree. So it is evident that this lack
of standards entails possibilities of constant controversy between
the shipper, the railroad, and the consumer.

Again, it is well known that the volume of crushed stone
shrinks in transit; and to make accurate estimates the engineer
should know the probable amount of this shrinkage. If a cer-
tain number of yards of tamped or consolidated stone are required
for a pier or for a certain length of macadam road, it is neces-
sary to know how many yards to order at the quarry so as to
have the required amount in the structure. As done at present,
the engineer to be on the safe side usually orders considerably
more than he thinks is enough, and even then he sometimes finds
he has not made allowance enough.

In order to establish a definite standard for the different sizes
and varieties of crushed stone, tests should be made until suffi-
cient data have been accumulated to determine a definite value for
the weight of a cubic yard of crushed stone under various condi-
tions, or to establish a coefficient by which either the weight of a

BAKER — WEIGHT OP CRUSHED STONE 3

cubic foot or a cubic yard of the solid stone, or its specific grav-
ity, can be multiplied to give the weight per cubic yard of crushed
stone. It is obvious that to make the results of the greatest
value will require a very large number of observations under
a variety of conditions. It is the purpose of this article to give
the results of a few tests along these lines.

Of the data hereinafter referred to, the observations on Ches-
ter stone and part of those on Joliet stone were made by Mr. Albert
J. Schafmayer, a senior student in Civil Engineering, during the
summer of 1906, while employed by the Illinois Highway Com-
mission in connection with constructional work. A brief sum-
mary of Mr. Shafmayer's results was published in the report
of A. N. Johnson, State Highway Engineer, in the first annual
report of the Illinois Highway Commission. The observations on
Kankakee stone and part of those on Joliet stone were made
by Mr. Benjamin L. Bowling, an employee of the Engineering
Experiment Station, during the fall of 1907. None of the inves-
tigations could have been made except for the generous cooper-
ation of the officials of the State Penitentiaries at Chester and
Joliet, and of the McLaughlin-Mateer Company of Kankakee.

Some observations were taken at Chicago and at Gary, Illinois,
but unavoidable conditions at these plants prevented a completion
of the work, and the results obtained are too incomplete to be of
any considerable value, and hence are not further referred to.

THE STONE

The observations referred to in this article relate wholly to
limestone, although in the appendix some data are given con-
cerning trap. The limestones experimented with were those quar-
ried at Chester, Joliet, and Kankakee.

The Chester stone is a rather coarsely granulated gray lime-
stone of the lower carboniferous group, and is quarried in the
grounds of the State Penitentiary at Chester, on the Mississippi
River, about half way between St. Louis and Cairo.

The Joliet stone is a compact, fine-grained magnesian lime-
stone of the Niagara series, and is quarried in the grounds of the
State Penitentiary at Joliet, about 40 miles southwest of Chicago.
The output of the crusher consists of 28 per cent 3-in. stone, 53
per cent 2-in., and 17 per cent Hn.

4 ILLINOIS ENGINEERING EXPERIMENT STATION

The Kankakee stone is a coarse-grained argillaceous lime-
stone of the Niagara group, and is quarried at Kankakee, on the
Kankakee River, about 55 miles south of Chicago.

DIVISIONS OF THE SUBJECT

The subject will be considered under the following heads:
I. Specific gravity; II. Absorptive power; III. Percentage of voids;
IV. Settlement in transit; V. Weight per cubic yard; VI. Coefficients
for determining the weight of crushed stone.

I. SPECIFIC GRAVITY

A knowledge of the specific gravity of a stone is useful in
determining the per cent of voids in broken stone; and the easi-
est way to determine the weight of a cubic unit of solid stone is
to find its specific gravity.

Wa

Specific gravity ~- Wa _ Ww

in which Wa is the weight of a fragment weighed in air, Ww the
weight of the same fragment suspended in water. If the
stone is porous to any considerable extent, the weight
in water should be determined so quickly that the absorption dur-
ing the weighing will be inappreciable.

Samples of stone were collected from the various parts of the
Joliet, the Kankakee, and the Chester quarries which were being
worked to produce the broken stone considered in the later parts
of this paper. The values of the specific gravity are given in

Table 1.

II. ABSORPTIVE POWER

A knowledge of the amount of water absorbed by a stone is
useful in determining the voids by the method of pouring
in water, and is also useful in correcting the weight of wet stone.

The absorption was determined by thoroughly drying a speci-
men, weighing it, immersing it in water for 96 hours, drying
with blotting paper, and weighing. The results are given in
Table 2.

III. PERCENTAGE OF VOIDS

The per cent of voids in broken stone of different sizes has an
important bearing upon the amount of cement and sand required

BAKER — WEIGHT OF CRUSHED STONE

TABLE 1
SPECIFIC GRAVITY OF LIMESTONE

Ref.
No.

Location
of
Quarry

Specific
Gravity

Observer

Position in Quarry

1

Joliet-

2.77

Schafmayer

Near Center. 4 to 6 ft. deep

2

"

2.78

"

it ti it it

3

"

2.70

tt

25 ft. W. of C., 4 ft. to 6 ft.

deep

4

11

2.69

1 1

n i t

5

a

2.72

1 1

E.

6

"

2.74

it

it i i

7

tt

2.71

a

N.

8

n

2.70

1 1

U ( - (

9

"

2.63

tt

S. " '

Mean

2.71

10

Joliet

2.74

Bowling

25 ft. S. of C. of floor 30^ft.

deep

11

"

2.68

"

u tt » u

12

it

2.74

tt

At '

13

"

2.73

1 1

<( i 11

14

"

2.69

tt

25 ft. N.

15

"

2.70

a

it it t it

Mean

2.71

16
17

Chester

2.67

2.58

Schafmayer

N. end over 25 ft. deep
50 ft. S. of the preceding,
over 25 ft. deep

18

u

2.59

1 1

100" " " "

19

tt

2.49

n

Center near top

20

"

2.66

a

N. end " "

21

tt

2.50

• '

0 ., .- It

22

It

2.48

tt

Center " "

Mean

2.57

23

Kankakee

2.62

Bowling

S. end at top

24

"

2.64

tt

U It It

25

«

2.65

it

20 ft. deep

26

u

2.65

1 1

u ti

27

It

2.56

*'

40 ft. "

28

It

2.56

14

u u

29

tt

2.60

U

N. at floor

30

tt

2.62

u

a tin

Mean

2.61

6

ILLINOIS ENGINEERING EXPERIMENT STATION

in making concrete; and the per cent of voids in connection with
the weight of a unit of solid stone is useful in determining the
weight of a unit of volume of broken stone.

The percentage of voids may be determined in either of two
ways: (1) by pouring in water; and (2) by computation from the
specific gravity and the weight of a volume of broken stone.

1. By Pouring in Water. Determine the weight of water a
given vessel will contain, then fill the vessel with broken stone,
and determine the weight of water that can be poured into the

TABLE 2
ABSORPTIVE POWER OF LIMESTONE

Ref.
No.

Kind
of

Stone

Weight
in Ib.
per
cu. ft.

Absorption

Position in Quarry

Ib. per
cu. ft.

Per cent
by
Weight

1

Joliet

170.66

1.23

0.72

25 ft. S. of C. of the floor, 30

ft. deep

2

166.98

.79

0.47

(I U I

3

170.85

.86

0.50

At Center '

4

170.41

1.25

0.73

tt . (, i

5

167.61

1.13

0.68

25 ft. N.

6

168.60

1.28

0.76

" " *

Mean

169.18

1.09

0.64

7

Kankakee

163.49

1.87

1.14

S. end at top

8

164.92

1.98

1.20

« «

9

165.11

2.66

1.61

" 20 ft. deep

10

165.30

2.81

1.70

(( U ((

11

159.81

4.49

2.81

" 40 ft "

12

159.68

4.67

2.92

U tl 44

13

162.24

2.99

1.84

N. at floor

14

163.73

2.85

1.74

44 It <l

Mean

163.04

3.04

1.84

15

Chester

167.0

.69

.31

16

4 4

165.8

1.22

.74

17

"

164.5

1.89

1.15

"

165.1

1.34

.81

18

"

161.5

2.54

1.57

19

U

161.5

2.34

1.45

Mean

164.2

1.67

1.01

BAKER — WEIGHT OF CRUSHED STONE 7

interstices of the broken stone. The ratio of the first amount of
water to the second is the proportion of voids.

In this method three sources of error require consideration,
(a). In pouring in the water, part of the contained air is not driv-
en out; and therefore the resulting per cent of voids is too small.
The error from this source may be reduced, if not entirely elimi-
nated, by pouring the stone into the water; but this procedure
introduces a new error, since the stone will not pack to the same
degree as in the ordinary method of filling a vessel or bin with
broken stone, and hence the result of pouring the stone into the
water will also give too large a per cent of voids. (&). If the
stone absorbs water during the test the apparent percent of voids
will be too great, (c). If the vessel has a wide mouth, as almost
necessarily it should have, there will be a likelihood of considerable
error in telling when the vessel is exactly full of stone and also
of water. The resulting error may make the per cent of voids
either too large or too small.

2. By Computation. Determine the weight of a known vol-
ume of broken stone. Compute the weight of an equal volume
of the solid stone by multiplying the known volume by the
weight of an equal volume of water and by the specific gravity of
the stone. The difference between the weight of the volume of
solid stone and that of the broken stone is the weight of stone
equal to the volume of the voids. The ratio of this weight to the
weight of the given volume of broken stone is the proportion of
voids.

This method is subject to the error of determining when the
vessel is exactly full of stone. In practice it is more complicated
than the preceding method, but it is more exact.

Table 3 gives the per cent of voids for three sizes of Chester
limestone determined by the two methods referred to above, by
two independent observers for different methods of filling the ves-
sels with broken stone; and Tables 4 and 5 the same for Joliet and
Kankakee limestone, respectively. In each case the results are
corrected for the absorption of the stone. Precautions were tak-
en also to eliminate absorption by the walls of the vessel used.
The distance of drop employed in filling the vessel corresponded
to that employed at the time in loading cars of broken stone.

ILLINOIS ENGINEERING EXPERIMENT STATION

TABLE 3
PERCENTAGE OF VOIDS OF CHESTER LIMESTONE

I

«H
O

6

I

cc

«H

o

1

•8 S

A ~

1

02 .

If

1.

M

Per Cent of Voids

By Pour-
ing in
Water

From
Specific
Gravity

3 *

o

I

3

O
$

>

By Use of Vessel Containing 27 cu. ft.

1
2
3

f-in. Scr.

15ft. drop

2430
2395
2435

3150
3095
3140

720

700
705

11.52
11.20
11.28

Mean

42.7
41.5
41.8

43.9
42.4

43.8

42.0

43.4

4
5

2 in.-f-in.

u -

15 ft. drop

u

2320
2375

3110
3165

790
790

12.64
12.64

Mean

46.8
46.8

46.4

45.8

46.8

46.1

6

7

3 in.-2 in.

15 ft. ^drop

2370
2390

3160
3185

• 790
795

12.64
12.72

Mean

46.8
47.2

45.3

44.8

47.0

45.0

By Use of Vessel Containing 2.6 cu. ft.

8
9
10

|-in. Scr.

u

Shoveled

< i

226.5
227.0
216.5

293
293

283

66.5
66.0
66.5

1.06
1.06
1.06

Mean

41.0
40.6
41.0

45.8
45.7

48.9

40.9

46.8

11
12

f-in. Scr.

it

214.5
210.5

286
284

71.5
73.5

1.14
1.17

Mean

44.0
45.2

48.6
49.6

44.6

49.1

13

"

20 ft. drop

229.0

293

64.0

1.025

39.4

45.2

14
15

2 in.-f-in.

Shoveled
20 ft. drop

204.0
237.0

286
306

82.0
69.0

1.31
1.10

50.5
42.5

51.2
43.3

16
17

3 in. -2 in.

Shoveled
20 ft. drop

212.0
245.0

291
313

79.0
68.0

1.265
1.09

48.7
41.8

49.3
41.3

BAKER — WEIGHT OF CRUSHED STONE

TABLE 4
PERCENTAGE OF VOIDS OF JOLTET LIMESTONE

1

•H
O

I

1

GQ

"o
1

2

be

'o -2
"o

o>
a

1
$

§5

If

eB

O1""1

*M r-j

'o

Per Cent of Voids

By Pour-
ing in
Water

From
Specific
Gravity

By Use of Vessel Containing 2.34 cu. ft.

1

2
3

Hn. Scr.
«

8 ft.^ drop

u

208.75
208.75
207.75

270.75
271.25
270.25

62.00
62.50
62.50

0.99
1.00
1.00

Mean

42.3
42.7
42.7

47.6
47.6
47.9

42.6

47.7

4
5

6

7

2 in;-Hn.

8 ft. drop

218.75
221.75
218.50
220.00

285.75
288.50
285.75
286.75

67.00
66.75
67.25
66.75

1.07
1.07
1.08
1.07

Mean

45.8
45.6
45.9
45.6

45.1
44.3
45.1

44.8

45.7

44.8

8
9
10
11

3 in.-2 in.

8 ft. drop

227.25
219.25
222.25

212.00

291.75

287.75
290.25

282.25

64.50
68.50
68.00
70.25

1.03
1.10
1.09
1.12

Mean

44.1

46.8
46.5
48.0

43.0
45.0
44.2
46.8

46.3

44.7

12
13
14
15

|-in. Scr.

4 ft. drop

u
u

215.75

218.75
209.25
208.25

276.00
279.25
273.00
272.25

60.25
60.50
63.75
64.00

0.96
0.96
1.02
1.02

Mean

41.1
41.3
43.5
43.7

45.8
45.1
47.5

47.7

42.4

46.5

16
17

18
19
20

2 in.-Hn.

u
(<

t (

4 ft. drop

it

II

u

203.00
209.75
209.75
212.25
213.25

277.25

283.25

282.75
283.75
284.00

74.25
73.50
73.00
71.50
70.75

1.19
1.15
1.17
1.14
1.13

Mean

50.7
50.2
49.9

48.8
48.3

49.0
47.4
47.4
46.7
46.5

49.6

47.4

21

3 in. -2 in.

4 ft. drop

221.25

291.25

70.00

1.12

47.8

44.5

By Use of Vessel Containing 2.43 cu. ft.

22
23
24

3 in. -2 in.

u

4 ft. drop

u
u

211.25
216.25
212.75

287.75
289.25

285.75

76.50
73.00
73.00

1.22
1.17
1.17

Mean

50.4
48.1
48.1

49.0

47.7
48.6

48.6

47.5

10 ILLINOIS ENGINEERING EXPERIMENT STATION

TABLE 5
PERCENTAGE OF VOIDS OF KANKAKEE STONE

€

0>

H

«M

o

0

*

<D
1

w

•8
1

33

i

Method
of Filling

!

02 .

«MJQ

0-*

£

o£

G1-*

Jl

«M 03

°^

^

M

<D

-1-3
rt

!s

*0^

4J

^

1.

s» •*-3

t£<~

°§

^

Per Cent of Voids

By Pour-
ing in
Water

From
Specific
Gravity

By Use of Vessel Containing 2.11 ou. ft.

I

2
3
4

f-in. Scr.

u
( (
( (

8 ft. drop
((

(i

it

189.50
192.25
186.00
183.25

242.75
244.75
237.50
235.25

53.25
52.50
51.50
52.00

0.85
0.84
0.82
0.83

Mean

40.3
39.7
39.0
39.3

45.9
45.1
46.8
47.6

39.5

46.4

5
6

li-in.-f-in.

u

8 ft. drop

a

193.50
197.50

253.50
258.00

60.00
60.50

0.96
0.97

Mean

45.4

45.8

44.7
43.6

45.6

44.2

7
8

2Hn.-li-m.

u

8 ft. drop
«

196.50
197.50

258.50

258.75

62.00
61.25

0.99

0.98

Mean

46.9
46.4

43.9
43.6

46.6

43.8

9
10

2i-in.-f-m.

1 1

8 ft. drop

u

202.25
201.50

260.50
260.50

58.25
59.00

0.93
0.94

Mean

44.1
44.6

42.2

42.4

44.4

42.3

By Use of Vessel Containing 1.15 cu. ft.

11
12

f-in. Scr.
«

8 ft. drop

u

100.00
103.75

129.25
132.75

29.25
29.00

0.47
0.46

Mean

40.9
40.5

47.5
45.6

40.7

46.6

13
14

IHn.-f-in.

u

8 ft. drop
«

104.25
104.50

137.50
136.75

33.25
32.25

0.53
0.52

Mean

46.5
45.1

45.4
45.2

45.8

45.3

15
16

2Hn.-f-in.

i 1

8 ft. drop

«

106.50
109.00

138.25
140.50

31.75
31.50

0.51
0.50

Mean

44.4
44.0

44.1
42.8

44.2

43.5

BAKER — WEIGHT OF CRUSHED STONE
TABLE 5 (Continued)

11

I

o>
c
o

43

be
1 1

I

0.0

II

(X>

^

5 .

Per cent of Voids

o

O

i E

<g£

— -:

*o^

o p

By Pour-

From

6

1

^ «M

^

^

J

. o

ing in

Specific

__

53

^

^g

^

1

Water

Gravity

By Use of Vessel Containing 0.694 cu. ft.

17

f-in. Scr.

8 ft. drop

63.00

79.75

16.75

0.27

38.5

45.5

18

"

63.50

80.25

16.75

0.27

38.5

45.1

Mean

38.5

45.3

19

2Hn.-li-m.

8 ft. drop

65.25

85.25

20.00

0.32

45.9

43.6

20

< i

66.50

86.25

19.75

0.31

45.4

42.5

Mean

45.6

43.0

Precautions were taken to prevent absorption of water by
fche sides of the vessel; and it is believed that there is no possi-
bility of error from this source in the data given in Tables 3, 4,
and 5. In some of the experiments the vessel containing the
stone was hauled from the chute to the scales on a wagon; and to
eliminate a possibility of error in weighing, the team was unhitched
while the weight was being taken.

Notice that the first part of Table 3 shows the percentage of
voids for the different sizes of stone; while the second shows the
variation due to the different methods used in filling the tub. An
inspection of the table shows that with each vessel the voids in-
crease with the size of the stone. It also shows that for both ves-
sels the average percentages are fairly uniform, the greatest vari-
ation being in the case of the 3-in. (3-in. to 2-in.) stone. In com-
paring the tests in which the 15- and 20-ft. drops were used, the
stone falling 20 feet invariably has a smaller percentage of voids
than that falling only 15 feet. The lower part of the table shows
that the voids were very materially less for the same size of stone
when the tub was filled by the 20-ft. drop, than when the
stone was shoveled in. These data show clearly that the density
increases with the fall. However, the tests were not sufficient in

12

ILLINOIS ENGINEERING EXPERIMENT STATION

number to justify an attempt to deduce a statement of the relation
of the height of fall to the density of the mass.

A comparison of the results in the last two columns of Table

3 shows that for screenings the method by pouring in water gives
a considerably smaller per cent of voids than by computation,
while for the 2-in. (2-in. to f-in.) and the 3-in. (3-in. to 2-in.)
sizes there is practically no difference by the two methods. Sub-
stantially the same conclusions may be drawn from Tables 4 and 5.

Summary of Voids: — A summary of the results in Tables 3,

4 and 5 is given in Table 6.

TABLE 6
SUMMARY OF PER CENT OF VOIDS

Per Cent.of Voids

Ref.
No.

Location
of
Quarry

Size of Stone

By Pour-
ing in
Water

From

Specific
Gravity

1

Chester

f in. Scr.

40.9

46.8

2

"

f in. Scr.

43.0

45.6

3

«

2 in. to |

in.

46.6

46.6

4

"

3 in. to 2

in.

46.1

45.1

5

Joliet

| in. Scr.

42.2

47.1

6

"

2 in. to |

in.

47.9

46.2

7

"

3 in. to 2

in.

47.5

46.1

8

Kankakee

f in. Scr.

39.6

46.1

9

"

U in. to

|in.

45.7

44.7

10

"

2± in. to

1 in.

44.3

42.9

11

2i in. to

liin.

46.2

43.4

IV. SETTLEMENT OF CRUSHED STONE IN TRANSIT

Sometimes crushed stone is bought by bulk, in which case it
may make a difference whether the volume is measured at the be-
ginning or at the end of the journey. Therefore experiments
were made to determine the settlement of crushed stone during
transit in wagons and also in railway cars.

Settlement in Wagons: — Observations were first made to
determine the relation between the settlement in wagons
and the distance hauled. An attempt was made to de-
termine the amount of settlement for regular increments

BAKER — WEIGHT OF CRUSHED STONE

13

in the distance hauled. This was done by stopping the
team and taking a measurement each successive 100 feet until
the settlement for that distance was too small to measure. The
measurements in all cases were taken by using two straight
edges, one placed across the top of the box and the other resting
on the top of the stone. Then as both straight edges were of the
same width, each measurement was taken from the top of the
upper one to the top of the lower one. Measurements were taken
near each side and on the center line, near the front, middle, and
back of the load, making a total of nine measurements for each
load.

The data for Chester limestone are given in Table 7. The
results vary surprisingly, — for example, compare tests No. 2 and
3, or 7 and 8, or 13 and 14. The haul was over about equal distances
on macadam, cinders, and earth. The results were obtained
within a day or two of each other, and it does not seem possible
that the smoothness of the roads could have changed materially
in the meantime. An attempt was made to drive equally care-
fully every time. About the only safe conclusions that can be
drawn from these data are: (l) about half of the settlement oc-
curs in the first 100 feet; and (2) the settlement at half a mile is
practically the same as that at a mile.

TABLE 7

EFFECT OF DISTANCE HAULED UPON SETTLEMENT IN WAGON
Experiments on Chester Limestone by Mr. Schafmayer

Test
No.*

Size of
Stone

Method of
Loading

Per Cent of Settlement for
Hauls ef-
fect

100

200

300

400

500

600

700

2640

5280

3

4
6
7
9
11
12
14

i in. Scr.f
ti

2 in. -fin.

u
«

3 in.-2 in.
it

u

15 ft. drop
(t

15 ft. drop

u

Shoveled

15 ft. drop

a

Shoveled

7.3
5.0
2.6
5.3
3.5
0.57
3.5
5.0

8.3

9.7
3.7
6.2
4.1
2.6
4.2
5.7

8.9
10.2
4.9
7.1
4.8
2.8
4.5
6.53

9.2
10.2
5.3
7.7
5.3
4.1
4.8
6.53

9.5
10.4
5.3
7.9
5.3
4.25
5.0
6.7

10.1
10.4
5.3
8.0
5.7
4.25
5.0
6.7

10.1
10.7
5.4
8.3
6.5
4.25
5.1
6.7

11.2
12.4
5.4
9.2
7.3
4.9
6.0
7.1

11.2
5.4

4.9
6.0
7.1

*These numbers refer to the series in Table 8.
tDusty.

14

ILLINOIS ENGINEERING EXPERIMENT STATION

The per cent of settlement of stone from three different lo-
calities for a haul of practically one mile is given in Table 8; but
the variation for any one size under identically the same condi-
tions (for example, compare the first three lines of the table) is so
great as not to warrant any attempt to draw conclusions. It was
not possible to secure more accurate data except by an expendi-
ture of time and money much greater than the value of the infor-
mation seemed to justify.

{Settlement in Cars: — The shortage of cars at the time
these experiments were made and the desire of the shipper
and also of the railway to hurry shipments forward
seriously interfered with the scope and value of these

TABLE 8
SETTLEMENT OF CRUSHED STONE IN TRANSIT IN WAGONS

ll

ho
1 1

O

m

Pi

Per Cent of
Settlement

I

0} O
•S *•*

wj

cc

s

OQ

1
£

Chester Limestone by Mr. Schafmayer

1

15 ft. drop

1.41

1.23

12.7

f-in. Scr.

1

Same for i mile

Mostly dust

2

15 ft. drop

1.41

1.25

11.4

f-in. Scr.

1

Same for i mile

3

"

1.41

1.25

11.4

"

1

u u u

4

11

1.41

1.23

12.7

•'

1

Stone dusty, wet

Mean

11.8

5

15 ft. drop

1.41

1.25

11.4

2-in.-| in.

1

Same for 2 miles

6

I 4

1.41

1.33

5.7

1

Same for •} mile

7

M

1.41

1.28

9.2

"

1

8

Shoveled

1.41

1.23

12.7

it

1

Same for | mile

9

11

1.41

1.31

7.1

"

1

Stone damp

Mean

9.2

10

15 ft. drop

1.41

1.27

10.1

3-in.-2 in.

1

A few tailings

11

"

1.41

1.34

4.9

4 I

1

Same for -J mile

12

"

1.41

1.32

6.4

*'

1

" " "

13

Shoveled

1.41

1.23

12.7

««

1.

A few tailings

14

< t

1.41

1.31

7.1

U

1

Same for | mile

Stone dirty

Mean

8.2

BAKER — WEIGHT OF CRUSHED STONE
TABLE 8 (Continued)

15

it

Method
of Loading

&$t

o>i

1**

&>i

Per Cent of
Settlement

og

£3
m™

•8

ll

^a
.2

Q

1

c3

5

09

tf

Kankakee Limestone by Mr. Bowling

15
16

*
*

1.80
1.61

1.61
1.46
Mean

10.6
9.3

f-in. Scr.

n

1
1

Chute at incline
of 30°

U (( «

10.0

17

18

•X-
•X-

1.80
1.61

1.67
1.45

Mean

7.2
9.9

li in.-f-in.

u

1

If

U (( U

u u u

8.6

Joliet Limestone by Mr. Bowling

19
20

4 ft. drop

< i

1.81
1.86

1.66
1.69

8.3
9.1

Hn. Scr.
.<

1
i

Chute at incline
of 45°

(( (( U

21

ii

1.81

1.63
Mean

9.9

n

i

ii U U

9.1

22

4 ft. drop

1.81

1.69

6.6

2 in.-Hn.

1

u « u

23

it

1.79

1.67

6.7

2 in.-Hn.

i

u u u

Mean

6.6

* Lower end of chute even with top of wagon bed.

experiments. (See Table 9). It will be noticed that the
settlement varies greatly for stone of the same size, loaded
the same day, and shipped to the same destination on the
same train, — for example, compare the second, third and fourth
lines of the table. The settlement was measured by the same
method as previously described for wagons, and was as carefully
determined as possible by that method. Part of the error is doubt-
less due to a variation in the freedom with which the crushed stone
ran out of the loading chute, and to a variation in the details of
the method employed in leveling off the load.

16

ILLINOIS ENGINEERING EXPERIMENT STATION

TABLE 9

SETTLEMENT OF CRUSHED STONE IN TRANSIT
IN KAIL WAY CARS

CC O

U

^H

pJi

if

1 cb£

Q> r-S C

O -M rj

| %S

J'go
GO -^

rjl

Destination

CD

^

Joliet Limestone by Mr. Schafmayer

1

8 ft. drop

2.4

2.4

0.0

|-in. Scr.

Springfield

149

2

8 ft. drop

2.4

2.2

8.3

u u

McLean

105

3

« it

2.0

1.75

12.5

U (.

u

u

4

u u

2.6

2.3

8.3

U (i

"

"

Mean

9.7

5

8 ft. drop

2.1

2.08

1.4

2 in.-i-in.

Springfield

149

6

u u

2.2

1.9

13.9

u u

"

Mean

7.6

7

8 ft. drop

2.3

2.1

8.7

U ((

McLean

105

8

« «

2.2

1.9

13.9

u u

"

u

9

• t u

2.7

2.5

7.4

(i U

(i

u

10

It U

2.6

2.33

9.7

u a

u

u

11

U <(

2.6

2.4

7.7

« «

"

(I

Mean

9.5

12

8 ft. drop

2.6

2.5

3.8

3 in.-2 in.

Springfield

149

13

U 11

2.6

2.3

10.5

u u

u

Mean

7.2

14

8 ft. drop

2.2

1.95

11.4

McLean

105

15

3.2

3.1

3.4

"

u

16

2.1

2.0

5.0

'•

<(

17

2.7

2.35

12.9

11

u

18

2.7

2.6

3.7

it

u

19

2.2

2.2

0.0

u

u

20

3.33

3.0

9.0

C(

u

21

2.3

2^05

10.8

1

u

22

2.7

2.5

7.4

4

11

23

2.7

2.45

9.2

1

u

24

2.7

2.4

11.1

I

"

25

2.6

2.35

9.6

'

u

26

"

2.2

2.0

9.1

u

11

Mean

10.2

BAKER — WEIGHT OF CRUSHED STONE
TABLE 9 (Continued)

17

6
5

4-3

GQ

£

T3 b£>

o a
lol

a 3

ls"L

bogVlg

ga^T

•S^l"

c3 cu X <D

&S*

<Un
|°ll

J-o 1

M £

Destination

* *
f«s

go_.

J 3

B

Joliet Limestone by Mr. Bowling

1

8 ft. drop

2.37

2.17

8.4

Hn. Scr.

Bloom'ton

91

2
3

u u
u u

2.52

2.80

2.31
2.62

Mean

8.3
6.4

2 in.-|-in.

U it

( (
<(

(1

U

7.4

4

u u

2.57

2.37

7.8

3 in.-2 in.

u

U

Chester Limestone by Mr. Schafmayer

1

2
3

15 ft. drop

U ((

< t u

3.00
2.75
2.50

2.7
2.4
2.25

Mean

9.5
12.5

9.8

i-in. Scr.

U 11

u u

Springfield

u
u

180

u
({

10.6

4
5
6

Barrows
15 ft. drop
Barrows

2.67
3.00

2.58

2.58
2.7
2.33

Mean

3.4
9.5

8.2

3 in.-2 in.

u u
u u

u
i (
u

i(
((

u

7.0

Kankakee Limestone by Mr. Bowling

1

8 ft. drop

2.27

2.15

5.4

2J in.-f in.

Bloom'ton

86

It is probable that part of the difference is due to the
difference in the care employed in switching the car from the load-
ing chute. At Joliet the cars were switched about a mile from the
crusher to the yards in the city, to be weighed; and at the time they
were weighed a casual examination was made of the settlement,
and the conclusion was drawn that from i to i of the total settle-
ment took place while the cars were being switched. The cars
were continually being moved while they were in the yard, and

18

ILLINOIS ENGINEERING EXPERIMENT STATION

hence more accurate observations could not be made as to the
effect of switching upon the settlement. The distance from
Joliet to McLean is 105 miles, and apparently a further haul of
44 miles to Springfield did not materially increase the settlement.
The great variations in results obtained under seemingly like
conditions make it unwise to attempt to draw any conclusions.
Apparently more tests must be made before any reliable conclu-
sion can be stated concerning the total amount of the settlement
or the law of its variation.

The depth of load in Table 9 is the mean of nine separate
measurements, and was computed to the nearest hundredth of a
foot although it is recorded only to the nearest tenth. The more
accurate values were employed in computing the per cent of settle-
ment. However, to eliminate any possibility of error in the arith-
metical work, the per cent of settlement was computed to a great-
er number of places than is justified by the data. A similar state-
ment applies to several of the tables in the subsequent parts of this
paper.

Summary of Data on Settlement: — A summary of the data in
Tables 8 and 9 is given in Table 10.

TABLE 10
SUMMARY OF DATA ON SETTLEMENT

Ref.
No.

Location
of
Quarry

Size
of
Stone

Settlement after a
Haul of

| mile or
more in
wagons

75 miles or
more in
cars

1
2
3
4

5
6

7
8
9

10
11
12

Chester

1 1

1 1
(i

Joliet
«

< *
«
f <

Kankakee

u

it

f-in. Scr.
f. « «

2 irk-f in. Scr.
3 in. -2 in. "

i in. Scr.

8 i< «

2 in.-i in. Scr.
2in.-i " "
3 in.-2 in.

f in. Scr.
li in.-f in. Scr.
2Jin.-f " "

12.7
11.8
9.2
8.2

9.1

10.6

7.0

8.4
9.7
7.4
9.5

7.8

6.6

10.0

8.6

5.4

BAKER — WEIGHT OF CRUSHED STONE 19

V. WEIGHT PER CUBIC YARD OF CRUSHED LIMESTONE

Broken stone is usually sold by weight even though the unit
is nominally the cubic yard, since it is the custom to determine
the number of cubic yards in a shipment by weighing the ship-
ment and dividing the total weight by the supposed weight of a
cubic yard. It does not appear that any adequate observations
have been made to determine the weight of a unit of volume of
the different sizes and kinds of crushed stone.

Tests to determine the weight of a unit of volume of crushed
limestone were made on stone from Joliet, Kankakee, and Chester,
both in wagons and in cars, at the same time the record was taken
of the settlement, as previously described.

Before beginning to load a car, measurements were taken
from a straight edge laid on top of the car body to the floor of
the car. These measurements were taken on each side of the car
and at the center transversely, and at each end and the middle
longitudinally. The stone was loaded into the cars by means of
a chute in the bottom of the bin. After the car was loaded the
upper surface was leveled off, and the depth of the stone below
the top of the car body was determined by measuring down from
a straight edge across the top of the car to a similar straight
edge lying on the crushed stone. Prom the above measurement
the volume of the stone was computed.

The cars were then switched to the scale track where they
were weighed by a representative of the National Weighing Asso-
ciation, each weight being verified by either Mr. Schafmayer or
Mr. Bowling. Prom these data the weight per cubic yard of the
loose stone was computed. Measurements similar to those made
at the crusher were taken when the car reached its destination;
and the weights per unit of volume of the stone when compacted
were computed as before.

The data and results of the observations on Joliet, Chester,
and Kankakee stone are given in Tables 11, 12 and 13 respectively.
For car loads, the "original weight" is after the car was
switched about a mile, and the "final weight" is after being
shipped 75 miles (a greater distance makes practically no differ-
ence); and for wagon loads the weights are at the loading bin and
after being hauled a half mile or more.

20 ILLINOIS ENGINEERING EXPERIMENT STATION

TABLE 11
WEIGHT PER CUBIC YARD OF JOLIET LIMESTONE

4-3 •
GO 0

&

«M

o o

<£> §

N£

£tt

•S2

s§

£3

cn

53 «f-| rrt

a^

.^6d

6*2

&

1!

fe o

U*

V

Eat

c3 . .

C£> 3

S~0

Car Loads by Mr. Schafmayer

1

|-in. Scr.

94500

36.0

36.0

2625

2625

2

«

75500

28.9

2612

3

u

94400

34.6

31.7

2730

2980

4:

ft

54700

20.9

18.2

2610

3000

5

u

96900

36.2

33.2

2680

2920

Mean

2652

2881

6

2 in.-|-in.

78700

30.6

30.2

2570

2600

7

«

69700

31.5

27.1

2210

2570

8

u

58500

24.8

22.7

2360

2580

9

«

54300

23.6

20.3

2300

2680

10

((

67500

31.0

29.1

2180

2320

11

u

82600

37.5

34.0

2200

2430

12

((

84400

37.5

34.8

2250

2430

Mean

2296

2516

13

3 in.-2 in.

92400

36.6

35.2

2520

2620

14

«

52700

23.0

2290

15

(i

102300

42.0

40.6

2440

2620

16

«

78600

31.8

2470

17

«

63050

25.2

23.6

2500

2670

18

«

66600

27.7

24.3

2380

2740

19

{(

88600

38.6

37.4

2300

2370

20

u

75800

31.6

- 31.6

2400

2400

21

u

94800

41.4

37.7

2290

2520

22

u

69000

30.0

26.4

2300

2610

23

((

87900

38.8

36.0

2270

2440

24

u

88300

38.8

35.4

2275

2490

25

((

86900

38.8

34.8

2240

2500

26

((

72800

32.2

28.8

2260

2530

27

u

88200

36.5

2420

28

It

91000

37.2

2426

29

u

91300

37.5

33.9

2430

2690

30

((

76800

31.3

28.5

2450

2700

Mean

2370

2564

BAKER — WEIGHT OF CRUSHED STONE

TABLE 11 (Continued)
WEIGHT PER CUBIC YARD OF JOLIET LIMESTONE

21

-J-3
02 O

H*

°§

<D O

2-2
S00

<*-£

o
. v

+3 C

fe- °

P-3

OJ

1'S'P
Sod

Ml>- 3

o^ °

feN

5^ >»

73 s

C W

5*8

1^

Ss^

Q^ o
^

4^

^ S'd

a>,

ls§

5

Car Loads by Mr. Bowling

31

f-in. Scr.

83800

31.52

28.85

2659

2905

32

33

2 in.-f-in.
«

82800
79600

34.40
33.64

31.82
30.82

Mean

2407
2366

2602
2583

2386

2592

34

3 in. -2 in.

58300

26.47

24.37

2202

2392

Wagons Loaded by Mr.

Bowling

35
36
37

i-in. Scr.

u
((

4195
4260
4165

1.81
1.86

1.81

1.66
1.69
1.63

Mean

2318
2290
2301

2527
2521
2555

2303

2533

38
39

2 in. -i-in.

u

4185
4150

1.81
1.79

1.69
1.67

Mean

2312
2318

2476
2485

2315

2480

It will be noticed that there is considerable variation in both
the original and the final weight per cubic yard. Notwithstand-
ing the variation it is believed that the number of observations is
so great as to make the means reasonably reliable; but the table
shows that the maximum error of any one observation may be as
much as 10 per cent, and hence great accuracy can not be expected
from a single observation. Similar results are shown for Chester
stone, — see Table 12. There are three errors that affect these
results: (1). Errors in determining the value of the stone at the
quarry and at the destination. (2). Errors in the weight of the
car as stenciled upon it. The original weight may have been de-

22

ILLINOIS ENGINEERING EXPERIMENT STATION

TABLE 12
WEIGHT PER CUBIC YARD OF CHESTER LIMESTONE

u

o>

M

™ &

=s.

£I£

eSt-i •

c oT5

So?
EZ 3

o °

•rtl

s*g

g&d

B o ^
#~d

S£°

iS*

-ti

.Remarks

Car Load by Mr. Schafmayer

1

i-in. Scr.

109100

41.97

38.0

2600

2870

Damp

2

u

70600

28.14

24.6

2509

2870

3

((

92900

36.72

.33.1

2530

2810

Mean

2546

2850

4

3 in.-2 in.

96500

41.60

38.2

2320

2530

Hand made

5

«

81500

32.91

31.8

2476

2560

Damp

Mean

2398

2545

6

3 in.-2 in.

106100

41.97

38.0

2528

2790

Wet

Wagon Loads by Mr. Schafmayer

7

i-in. Scr.

3550

1.41

1.23

2518

2886

15 ft. drop

8

3550

1.41

1.25

2518

2840

15 ft. drop

9

3460

1.41

1.25

2450

2770

15 ft. drop

10

3420

1.41

1.23 2425

2780

15 ft. drop

11

2430

1.00

2430

No haul, 15 ft. drop

12

2395

1.00

2395

No haul, 15 ft. drop

13

2435

1.00

2435

No haul, 15 ft. drop

Mean

2453

2819

14

2 in.-f-in.

3360

1.41

1.28

2380

2625

15 ft. drop

15

a

3250

1.41

1.23

2305

2642

Shoveled

16

u

3460

1.41

1.33

2450

2600

15 ft. drop

17

( i

3200

1.41

1.31

2270

2445

Shoveled

18

u

2375

1.00

2375

No haul, 15 ft. drop

19

((

2320

1.00

2320

No haul, 15 ft. drop

20

«

3250

1.41

1.25

2305

2600

No haul, 15 ft. drop

Mean

2444

2582

21

3 in -2 in.

3200

1.41

1.23

2270

2601

Shoveled ~

22

3330

1.41

1.33

2360

2505

15 ft. drop

23

2390

1.00

2390

No haul, 15 ft. drop

24

3480

1.41

1.34

2470

2595

15 ft. drop «*«~~^

25

3290

i.41

1.31

2335

2510

Part dirt, shoveled

26

2370

1.00

2370

No haul, 15 ft. drop

27

3350

1.41

1.27

2376

2638

15 ft. drop

Mean

2367

2570

BAKER — WEIGHT OF CRUSHED STONE

23

termined when the car was wet; while in the observations under
consideration the cars were dry. (3). In weighing a string of
cars, either empty or loaded, there is some error due to the action
of the coupler.

Table 11 shows that the weight per cubic yard of screenings
is more than that of coarser stone, but also shows that 3-in. stone
weighs more per cubic yard than 2-in. Similar results obtained
for wagon loads, and also for Chester and Kankakee stone, both
for car loads and for wagon loads — see Tables 12 and 13.

TABLE 13
WEIGHT PER CUBIC YARD OF KANKAKEE LIMESTONE

6

I

^

0

*o

gi

*t

2

ft

DQ

•4-3 '""'

^>

o r^

3

^ d -s

«H
0

§§

15 •

£ ^

1 2

<a

03 S_

1

H

<D

1?

5^"^ r^
°

§ °

•I-H Q)

jSOft

S ^

3

f»

5

o£

£

Car Load by Mr. Bowling

1

2iin,f-m.

62900

27.83

26.32

2260

2390

Wagon Loads by Mr. Bowling

2

f-in. SCT.

4085

1.80

1.61

2270

2537

3

"

4170

1.61

1.46

2590

2856

Mean

2430

2697

4

H in.-t in.

3840

1.80

1.67

2133

2299

5

u

4050

1.61

1.45

2516

2793

Mean

2325

2546

Summary of Weights: — Taking an average of the preceding
results for each size of stone from each quarry the summary
shown in Table 14 is obtained.

24 ILLINOIS ENGINEERING EXPERIMENT STATION

TABLE 14

SUMMARY OF WEIGHTS OF CRUSHED LIMESTONE
Results in Pounds per Cubic Yard

Wagon Loads

Car Loads

Ref.

No.

Location
of
Quarry

Size
of
Stone

+=S
*•$

**2i

«!

« C/5

-1S2

4D £j

£|

5|1§

^1

^||S

1

Joliet

|-in. Scr.

2303

2533

2659

2905

2

"

f-in. Scr.

2652

2882

3

"

2 in.-i-in.

2315

2480

2386

2592

4

"

2 in.-|-in.

2296

2516

5

"

3 in.-2 in.

2361

2553

6

Chester

f-in. Scr.

2442

2797

2546

2850

7

"

2 in.-f-in.

2344

2582

8

"

3 in.-2 in.

2367

2569

2348

2545

9

Kankakee

f-in. Scr.

2430

2697

10

"

li in.-f-in.

2325

2546

11

"

2i in.-f-in.

2260

2390

Relations between Actual a?td Nominal Weight of Crushed Stone. —
As is well known, it is the universal custom to load a car more
than its rated capacity; and similarly it seems to be the custom of
laborers when loading a car with crushed stone, to put in more
than directed. This fact causes an erroneous idea of the weight
of a yard of the material among the railway officers, as they weigh
the car and divide the weight of the stone by the nominal number
of yards to obtain the weight per cubic yard. Since the actual
volume is not measured, the number of yards is taken from the
bill of lading submitted by the shipper, which is approximate and
is usually too small; and consequently the weight per cubic yard
derived by this method is usually somewhat too great. For ex-
ample, the Superintendent of the Wabash, Chester and Western
Railway weighed a large number of cars of stone at Chester, and
obtained by this method weights of 2600 pounds and over per
cubic yard. In all his observations the number of yards was
taken as given on the bills.

BAKER — WEIGHT OF CRUSHED STONE

25

To determine the relation between the actual weight of
crushed stone and the weight found as above, accurate measure-
ments of ten cars being loaded at Chester were made by Mr.
Schafmayer to ascertain if the high weights per cubic yard ob-
tained by the railroad were due to overloading. The results of
these tests are shown in Table 15. In every case the actual con-
tents of the car are greater than the number of yards in the bill.
The average excess is 1.71 yards for an average nominal load of
26 yards, an average excess of 6.6 per cent. This gives an appar-
ent average weight of 2558 pounds for a yard actually weighing
only 2400 pounds. It can be readily seen that under such con-
ditions, it is not surprising that railway officials have an exag-
gerated idea as to the weight of a cubic yard of crushed stone.

TABLE 15
EXCESS OF ACTUAL LOADING IN CARS. OVER BILLING

CO g

o5 w

43

J -d

43 T3

.

^S'o &

*j§ 5

S lj§ I?

* *

C.Q ^

tfft

•g gS'g

£ 1"° •

*0^^g

^ M

1^§

c« r3

^^CQj

"^fc O

6 C3 °^

& ^

o g

S"^ ^

!^^

^5*^

<1 ft

ft

1

25

25.7

0.7

2.8

2420

2488

2

25

25.7

0.7

2.8

2420

2488

3

25

27.7

2.7

10.8

2420

2684

4

25

27.7

2.7

10.8

2420

2684

5

25

27.7

2.7

10.8

2420

2684

6

25

25.8

0.8

3.2

2420

2510

7

30

32.0

2.0

6.7

2420

2583

8

25

25.7

0.7

2.8

2420

2488

9

30

31.4

1.4

4.7

2420

2534

10

25

27.7

2.7

10.8

2420

2684

AY.

26

27.71

1.71

6.6

2420

2581

VI. COEFFICIENTS

FOR DETERMINING WEIGHT OF CRUSHED
STONE

In the introduction it was suggested that possibly coefficients
could be determined by which to deduce the weight per unit of
volume of crushed stone when the weight of a unit of solid stone
or the specific gravity was known. Table 16 shows such coeffi-
cients for the various sizes for three kinds of stone, at the crusher
and also at the destination, both in cars and in wagons. The

26

ILLINOIS ENGINEERING EXPERIMENT STATION

TABLE 16

COEFFICIENTS BY WHICH TO DETERMINE THE WEIGHT IN POUNDS
PER CUBIC YARD OF CRUSHED LIMESTONE

Kind
of
Stone

Size
of
Stone

Having- the
Weight of a
Cu. Ft. of
Solid Stone

Having the
Weight of a
Cu. Yd. of
Solid Stone

Having the
Specific Gravity

3

i^

«*H oTp
o a o

^1

Coeffi-
cient

f*

S3

$

Coefficient

. <D

*H C

Oo

d^

GO'S

Coefficient

N

c3
0

1

FH
0

I

£

1

c
o
bt
c9

Chester

Joliet
«

Kankakee

Mean
Kankakee

Chester

Joliet
«

Kankakee •
Mean

Chester
Joliet

Mean

Chester

Joiiet
(i

Kankakee

Mean
Kankakee

Chester

Joliet
tt

Kankakee
Mean

Chester
Joliet

Mean

|-in. Scr.
i-in. Scr.
f-in. Scr.
Hn. Scr.

We

160.4
169.1
169.1
162.8

,ight
15.9
15.7
15.4

at <
15.3
13.6

14.9

3rusl
4331
4566
4566
4397

ier

0.588
0.582
0.572

0.566
0.504

0.553

2.57
2.71

2.71
2.61

990.7
981.2
963.8

954.5

849.8

931.0

Hn. Scr.
lirin.-fin.

2 in.-|-in.
2 in.-Hn.
2 in.-f-in.
2iin.-t-in.

165.4
162.8

160.4
169.1
169.1
162.8

15.7

14.1
13.6
13.9

13.9

14.9
14.0

14.6
14.3

14.6
13.7

14.2
14.8

4465
4397

4331
4566
4566
4397

0.581

0.523
0.503
0.514

0.541
0.529

0.541
0.507

2.65
2.61

2.57
2.71
2.71
2.61

978.6

880.4
847.2
865.9

911.8
890.8

912.1
854.2

2 in. 4 in.

3 in.-2 in.
3 inx-2 in.

165.4

160.4
169.1

4465

4331
4566

0.513

0.554
0.517

0.524
0.546

2.65

2.57
2.71

864.5

933.1

871.2

883.2
921.0

3 in.-2 in.

f-in. Scr.
|-in. Scr.
|-in. Scr.
|-in. Scr.

164.8
Weig
160.4
169.1
169.1
162.8

14.4
ht a

17.8
17.2
16.9

14.8
t De
17.6
15.0

16.6

4448
.stint
4331
14566
'4566
4397

0.536
ition
0.658
0.636
0.625

0.546

0.651
0.555

0.613

2.64

2.57
2.71
2.11
2.61

902.2

1108.9
1072.0
1053.5

921.0

1096.9
934.7

1033.3

i-in. Scr.
liin.-f-in.

2 in.-f-in.
2 in.-Hn.
2 in.-S-in.
2Jin.-|-in.

165.4
162.8

160.4
169.1
169.1
162.8

17.3

15.3
14.9
14.7

16.6
15.6

16.1
14.7

4465
4397

4331
4566
4566
4397

0.640

0.568
0.551
0.544

0.606
0.579

0.596
0.543

2.65
2.61

2.57
2.71
2.71
2.61

1078.1

956.5
928.4
915.7

1021.6
975.5

1004.7
915.1

2 in.-Hn.

3 in.-2 in.
3 in.-2 in.

165.4

160.4
169.1

15.0

15.9
15.1

15.4
16.0

4465

4331
4566

0.554

0.588
0.559

0.570
0.593

2.65

2.57
2.71

933.5

990.2
942.0

959.9
1000.0

3 in.-2 in.

164.8

15.5

16.0

4448

0.574

0.593

2.64

966.1

1000.0

BAKER — WEIGHT OF CRUSHED STONE 27

means are stated in Table 16 in such a manner as to show the
average result *f or each size.

Disregarding whether the stone is measured in a car or a
wagon, and also disregarding whether it is measured at the crush-
er or at its destination, the following summary of Table 16 is ob-
tained.

MEAN COEFFICIENT BY WHICH TO MULTIPLY

nip o™^ THE WEIGHT OF A CUBIC FOOT OF SOLID

LIMESTONE TO OBTAIN THE WEIGHT OF A
CUBIC YARD OF THE CRUSHED STONE

i-in. screening's 15.5

2 in. to i inch 14.6

3 in. to 2 inch.. 15.2

Average 15.1

Notice that the coefficient is largest for the finest stone, and
smallest for the intermediate size. The same is true for trap
(see Table 17) even though the sizes slightly differ. This seems
to prove that the weight of screenings is greater than that of
coarser stone, while the weight of the intermediate size is less
than that of either extreme size.

28 ILLINOIS ENGINEERING EXPERIMENT STATION

APPENDIX I
WEIGHT OF VOIDS OF CRUSHED TRAP

A careful search has been made of engineering literature, and
below is the only definite information discovered.

In the Journal of the Association of Engineering Societies,
Volume 11 (1892), page 424, W. E. McClintock, at present Chair-
man of the Massachusetts Highway Commission, gives an account
of six experiments made by him to determine the weight of a unit
of volume of crushed trap. In the first experiment he weighed
the contents of a bin holding 29i cubic yards,* and found the
weight of stone that had passed a i-inch screen to be 2605 pounds
per cubic yard, and in another test under the same conditions,
to be 2690 pounds; and when the broken stone was wet the weight
was 2480 pounds per cubic yard. In another experiment he
weighed the stone in a bin holding 89.8 cubic yards, and found
the weight of stone that had passed a 1^-inch screen and had
been caught on a i-inch screen to be 2423 pounds per cubic yard.
In a third experiment he weighed the stone in a bin containing
89.7 cubic yards, and found the weight of the stone that had
passed a 3-inch screen and had been caught on a It-inch screen to
be 2522 pounds per cubic yard. He also measured six cars and
weighed the contents, and found the weight of the last mentioned
size to be 2531 pounds per cubic yard. The following statement
shows the relative proportions of the several sizes of crushed
trap.
SIZE OF STONE PER CENT

i-inch screenings 13.24

H inch to i-inch , 23.89

3 inch to 1| inch 62.87

Total output of crusher 100.00

Prom the weight per cubic foot of solid stone given by Mr.
McClintock and the above weights of the broken stone, the per
cent of voids was computed. A summary of Mr. McClintock's
experiments is given in Table 17, and the coefficients for trap
are given in Table 18.

*Mr. McClintock privately informed the writer that the average drop of the stone into
the bins was about 8 feet.

BAKER — WEIGHT OF CRUSHED STONE

TABLE 17
WEIGHT AND VOIDS OF CRUSHED TRAP

29

Kef.
No.

Size of Stone

Weight
in Ib. per
cu. yd.

Per Cent
of Voids,
computed

1
2

i- in. Screenings, in bin, dry

u u «

Mean

2605
2690

46.5

2648

3

in bin, wet

2480

4

1| in. to | in. in bin

2432

50.2

5
6

3 in. to li in. in bin
in cars

Mean

2522
2531

48.1

2526

TABLE 18

COEFFICIENTS BY WHICH TO DETERMINE THE WEIGHT IN
POUNDS PER CUBIC YARD OF CRUSHED TRAP

Kef.
No

Size of Stone

Having the
Weight of a
Cubic Foot of
Solid Stone

Having the
Weight of a
Cubic Yard of
Solid Stone

Having the
Specific
Gravity

Wt. of

Wt. of

Sol. Stone

Coeffi-

Sol. Stone

Coeffi-

Specific

Co-

Ib. per
cu. yd.

cient

Ib. per
cu. yd.

cient

Gravity

effi-
cient

1

i-in. screenings

180.7

14.6

4879

0.541

2.90

914.4

2

1} in.-i in.

180.7

13.5

4879

0.500

2.90

839.7

3

3 in.-U in.

180.7

13.9

4879

0.515

2.90

872.2

Mean

13.7

0.519

875.4

THE

UNIVERSITY 1

OF

PUBLICATIONS or THE ENGINEERING EXPERIMENT STATION

Bulletin No. 1. Tests of Reinforced Concrete Beams, by Arthur N. Talbot. 1904. (Out
of print.)

Circular No. 1. High Speed Tool Steels, by L. P. Breckenridge. 1905.

Bulletin No. 2. Tests of High-Speed Tool Steels on Cast Iron, by L. P. Breckenridge
and Henry B . Dirks. 1905.

Circular No. 2. Drainage of Earth Roads, by Ira O. Baker. 1906.

Bulletin No. 3. The Engineering Experiment Station of the University of Illinois, by
L. P. Breckenridge. 1906. (Out of print.)

Bulletin No. 4. Tests of Reinforced Concrete Beams. Series of 1905, by Arthur N.
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Bulletin No. 5. Resistance of Tubes to Collapse, by Albert P. Carman. 1906. (Out of
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Fuel Tests with Illinois Coals, by L. P. Breckenridge, S. W. Parr and

Tests of Concrete: I. Shear; II. Bond, by Arthur N. Talbot 1906. (Out

6.

Bulletin No. 7.
Henry B. Dirks. 1906.

Bulletin No. 8.
of print.)

Bulletin No. 9. An Extension of the Dewey Decimal System of Classification Applied
to the Engineering Industries, by L. P. Breckenridge and G. A. Goodenough. 1906.

Bulletin No. 10. Tests of Concrete and Reinforced Concrete Columns, Series of 1906, by
Arthur N. Talbot, 1907.

Bulletin No. 11. The Effect of Scale on the Transmission of Heat through Locomotive
Boiler Tubes, by Edward C. Schmidt and John M. Snodgrass. 1907. (Out of print.)

Bulletin No. 12. Tests of Reinforced Concrete T-beams. Series of 1906, by Arthur N.
Talbot. 1907.

Bulletin No. 13. An Extension of the Dewey Decimal System of Classification Applied
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Bulletin No. 14. Tests of Reinforced Concrete Beams. Series of 1906, by Arthur N.
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Bulletin No. 15.

Bulletin No. 16.

Bulletin No. 17.
Wheeler. 1908.

Bulletin No. 18.

Bulletin No. 19.

How to Burn Illinois Coal without Smoke, by L. P. Breckenridge. 1908.

A Study of Roof Trusses, by N. Clifford Ricker. 1908,

The Weathering of Coal, by S. W. Parr. N. D. Hamilton, and W. F.

The Strength of Chain Links, by G. A. Goodenough . 1908.
Comparative Tests of Carbon, Metallized Carbon and Tantalum Fila-
ment Lamps, by Thomas H. Amrine. 1908.

Bulletin No. 20. Tests of Concrete and Reinforced Concrete Columns, Series of 1907, by
Arthur N. Talbot. 1908.

Bulletin No. 21. Tests of a Liquid Air Plant, by C. S. Hudson and C. M, Garland. 1908.
Bulletin No. 22, Tests of Cast-Iron and Reinforced Concrete Culvert Pipe, by Arthur N.
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Bulletin No. 23. Voids, Settlement and Weight of Crushed Stone, by Ira O. Baker. 1908.

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