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115
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HE COST OF PRODUCING.

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BITUMINOUS PLANT MIXES

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heais (for the, Degrge. oft-B
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I.

The Cost of Producing
Bituminous Plant Mixes

A Thesis Submitted to
The Faculty of
MICHIGAN STATE COLLEGE
or
AGRICULTURE AND APPLIED SCIENCE

by

Arthur Harvey Eggch

Candidate for the Degree
of

Bachelor of Science

June 1940

Acmovmrncmmms

In submitting this thesis to the Faculty of Michigan

State College, I wish to thank Mr. Mabbott, for his ex-

cellent advice and guidance in this problem, and Mr. Timchan

of American Bitumals Company, for the oils which his company

furnished me for preparing my samples. I also wish to ex-

press gratitude to the following companies which furnished

bulletins and prices for the materials used in the thesis:

The
The
The
The
The
The
The

Iowa manufacturing Company, Cedar Rapids, Iowa.
Barrett Company, New York, New York. I

Toledo Vitrified Brick Company, Toledo, Ohio.

W. H. Anderson Company, Detroit, Michigan.
Construction machinery Company, Waterloo, Iowa.

Blew Knox Company, Pittsburgh, Pennsylvania.
Anderson Sand and Gravel Company, Saginaw, Michigan.

Hetherington and Berner Company, Indianapolis, Indiana.

Bituminous mixed aggregate roads have been built
successfully in the United States and EurOpe for many years.
Due to the great increase in automobile traffic during the
last decade, the secondary roads are needing better and more
lasting surfaces. The black-top road is being used more and
more to improve these secondary, farm.to market, roads.

Because of the increased popularity of this material
with highway departments, and, since it is the author's hope
to be building some of these roads in the future, the writer
has set out to determine, to the best of his present know-
ledge, ”the cost of producing bituminous plant mixes,” and
their suitability for stockpiling without becoming unwork-
able.

The prices used in computing costs were collected from
companies manufacturing, producing, or refining the materials.
These unit prices may not be exact, but are representative
for this problem.

At the very beginning of the problem, sieve analyses
were run on the available aggregate and filler so as to
know what per cent of each size was present. Later these
materials will be proportioned together so the final ‘
mixture will lie within the limits of size as required by
Specifications as set up by the American Bitumals Company
for the emulsion, and the Nebraska State Highway Depart-
ment for the aSphaltic oils.

The Nebraska specifications were used, as they were

used in the highway material and testing course. The

-2-

final proportions of these materials fit the above spec-

ifications better than they do the Michigan Specifications.
The average of the several analyses of each material

available showed the following pr0portions retained on the

sieves. A plot of these values is shown on plate I.

% Retained on Sand Stone Filler
1% inch square opening - 0. -
1 inch square opening - 41.9% -
3/4 inch square Opening - 86.0% -
3/8 inch square Opening 0 97.9% -
4 Sieve 1.9% 99.0% -
10 Sieve 21.7% 99.5% -
20 Sieve 36.4% 99.5% -
40 Sieve 61.7% 100 % 0.24%
60 Sieve 85.6% 100 % 0.64%
140 Sieve 98.8% 100 % 19.16%
200 Sieve 99.65% 100 % 41.20%
Passing 200 sieve 0.85% o % 58.80%

The materials cost $6.00 for filler, 65 cents for stone,
and 30 cents for sand.

With the preliminary work completed, and with the
average results of sieve analyses tabulated, the task of
. proportioning the materials together to meet the require-
ments as stated in specification H-lS for Bitumals Cold
Mixed Asphaltic Concrete Pavements as published by the

-3-

3202.2. 2.5.; $2.53 ”1.2.33 mammEDZ u>u_m om<oz<hm mw4>._.

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‘ .5 \ 3.5.5 zo.n¢u>zou 29533 N)!»
.. .x 5.. 20:23.” 1.13. . .dtfiKUQXU 07=¢UM7=OZU

American Bitumals Company. The grading of mineral aggregate

for Type C regular surface has the following requirements:

% retained, 1% inch square screen 0%

% retained, 3/4 inch square screen 0 - lO
% retained, t inch square screen 0 - 20
% retained, i inch square screen 15 - 40
% retained, No. 10 sieve 45 - 60
% retained, No. 40 sieve 65 - 85
% retained, No. 80 sieve 80 - 90
% retained, No. 200 sieve 92 - 97

After several trials, the final gradation which fell
within the limits as stated above was arrived at, in which
58% sand, 35% stone, and 7% filler were used. This
gradation is plotted in Plate II.

The cost of this mixture is $0.8315 per ton.

 

 

 

; ’Retained

NMter-: % g : : : : : : : : :

ial :Used; 3/4 :3/8: 4 : 10 : 20 : 4o : 60: 140 :200 :Pass
.__ 3 : .i__ : : s _L : _L 1; : 200
Sand : 58 g i i 1.1:12.6 :21.2 :55.0 :50.0:57.5 :58 :
Stone : 5 i 5 i 5: 5 i 5 i 5 i 5 i 5 i 5 i 5 :
Stone : 18 i :18: 18 g 18 i 18 i 18 i 18 i 18 :18 i
Stone : 12 i i i 12 i 12 i 12 i 12 i 12 i 12 :12 :
Filler: 7 i g g i g i i i 1.3 i 3 i 4

i g 5 :23i36.1:47.6 :56.2 :71.0 :85.0:93.8 :96.0:4.0

9NISSVd .LNEDHEd

352.328.362.220 maxed» . mmmmEDZ m>u_m om<oz<km mu4>h

I C.

 

e
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5. mm a. w. . . K... e e z s u m m m m. w w m
3.62. z. curquoIozEEo «(.5050 mmmmEDZ u>m_.m om<oz<kw .m .3

 

.5310 29952.30 n.n>...<2( u>u.n
ZO..P(.PW I_(.‘...MS=KU1XM OZ.EUU7=02U

The material for the aSphaltic oil was proportioned
to meet the gradation.B of Nebraska specifications:

Minimum Maximum

% retained on 3/4 inch screen 0 - 5
% retained on No. 10 Sieve 30 - 60
% retained on No. 20 Sieve 45 - 65
% retained on No. 50 Sieve 60 - 80
% retained on No. 100 Sieve 70 - 90
% passing No. 200 Sieve 5 - 20

After several more trials, a gradation was arrived at
with 50% sand, 25% stone, and 25% filler which fell within
the limits as above stated. The cost of this mixture is
31.8125 per ton. These results as tabled below are plotted
on Plate III:

 

 

 

 

E % Retained

3 3 3 3 3 3 3 3 3 3PaSS'
Mater-z % : : : : : : : : : zins
_ia1 :Used:3/4:3/8: 4 : 10 : 20 : 40 : 60 : 140: 200:200
Stone : 16 E 0 E16 : 16 : 16 E 16 E 16 E 16 E 16 E 16 E

3 3 3 3 3 3 3 3 3 3 3

Stone : 9 : : : 9 : 9 : 9 : 9 : 9 : 9 : 9 :
Sand E 50 E E E .9 E10.8E21.0E50.8E 42.9 E 49 E 50 E
Filler; 25 E E E E E E 0,6E 1.6 E4.9 E10.5E14.7

E 0 E16 E25.9:85.8E46.0E59.4E 68.6 E7 °

8.7:85.5E14.7

The bituminous materials which are standard were furnished
by the’American Bitumals Company. The bitumals HRM sample is
an emulsion of 58% hard aSphaltic material and water contain-

ing a small amount of emulsifying agent. The RC-2 sample is an

-7-

1‘1“

.1 3‘1“

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.72.»..\.K 29.52...." J<u...u2.mmmxu 02Euwz.ozu

asphalt cement which has been rendered fluid by fluxing with
a naptha type distillate. The MC-3 sample is an a8pha1t
cement fluxed with a kerosene type of distillate. The SC-6A
is an asphaltic residual oil which will not volatilize
readily. The list price for these oils as quoted f.o.b. at

Saginaw, Michigan in tank car quantities was:

Bitumals HEM 9.57 cents per gallon
R. C. - 2 7.90 cents per gallon
M. C. - 3 7.90 cents per gallon
S. C. - 6A 7.40 cents per gallon

These oils are added to the aggregate mixture to bind the
fines and the coarse materials together.

The per cent of bitumals to be used is calculated from
an empirical equation.made up by the experience of the

American Bitumals Company.
P - 0.05 A % 0.1 B { 0.5 c

P is TOtal per cent by weight of Bitumals based on
the weight of the graded mixed aggregate.

A is The per cent of the mineral aggregate retained
on a number 10 sieve.

B is The per cent of mineral aggregate passing a
number 10 sieve and retained on'a number 200 sieve.

C is The per cent of the mineral aggregate passing a

number 200 sieve

-9...

(0.05) (47.6) (0.1) (85 - 47.6) / (0.5) (4)

2.38 ; 5.74 i 2.00
z 8.12%

The per cent of asPhaltic oil is also calculated from

an empirical formula made up by experience of the Nebraska

State Highway Department.

in which:

P

P

= AG (0.02s) % .06b 4 0.10 % Sd

is the percent by weight of Bfiumen required in the
Bituminous Mixture prior to laying.

is the percent of aggregate retained on the number
50 sieve.

is the percent of aggregate passing the Number 50
sieve and retained on the number 100 sieve.

is the percent of aggregate passing the number 100
sieve and retained on the number 200 sieve.

is the percent of aggregate passing the number 200
sieve. .
is a factor depending upon the fineness and absorp-
tive capacity of the material passing the number 200
sieve. Generally, a value of 0.2 may be used for

"S".

"A" is an absorption factor for the aggregate. This

factor will be determined on the basis of the
aSphaltic material and aggregate selected for each
project. The factor should be applied to the
portion of the combined aggregate Which is

absorptive. -10-

The bulk Specific gravity was determined by taking a
1/10 cubic foot container and tamping the aggregate into
the cylinder. The weight of this material in the cylinder
was 6010 grams from which the weight per cubic foot is
60,100 grams.

Bulk Specific Gravity 3 g2 : Wt. per 0%. ft. :
Wt. cu. t. water

 

(60100)(2.ZQ§) : 2.13
62:4

Bulk Specific Gravity of Plate River Gravel 3 g1 Z 2.62

Gravity Correction Factor : G 2 5‘ 3 2.62 : 1.23
82 20
P ; AG (0.02a) % (0.06)b # (0.1) c / Sd

(1) (1.23) (0.02) (65) f (0.06) (11) f (0.1) (9.3)

¢ (0.2) (14.7)

1.60 % 0.66 K 0.95 # 3.54
6.73%

Since the factor P is % bitumen by weight, it is
necessary to change this due to the fluxing material in the
bituminous material as it is applied to aggregate. This

formula corrects for the bituminous material used

N a 100 PK
IOO-P

in which:
N = Percent of Bituminous material to apply to the

combined aggregate.

-11..

K is a factor which depends upon the type of Bitumdnous

used, and

 

using RE 011, K = 1.2
2 100 6073 1.2 : 8.66%
100 - 6.
using MC oil, K = 1.1
= (100) (6.73) (1.1) : 7.93%
100 " 6073
using SC oil, K = 1.0
N 8 100 6.73 1.0 : 7.22%

00 - 6.

The percent by weight of sand, stone, and filler needed
to give the desired gradation for laboratory use are weighed
out pr0portionately so to make a sample whose final weight
is 30 pounds.

16% stone, 3/4 to 3/8 or 4.8 lbs.
9% stone, 3/8 to No. 4 sieve, 2.7 lbs.

 

50% sand, 15.0 lbs.
25% filler, 7.5 lbs.
30.0 lbs.

These materials were added together and mixed dry for
a few minutes to get a uniform.mixture, then the aggregate
was heated to a temperature of 500 Centigrade. The oil was
added slowly while the material was mixed with trowel and
hands. The trowel Just turned over the material and did

not do very much mixing, while the fingers acted more like

. -12-

'.

pug mill teeth and completely coated the particles with a
thin film of oil. The mixture was allowed to cure for a
few days, and then a trowel was used to pile the material
up. When this was done, the particles would slowly roll
down one stone to another as though the mass was crawling.
There is no rapid sliding, but a slow, steady, worm-like
movement. The particles finally settle into a position
where they will remain until the mixture is stirred again.

To ascertain which material is more stable when comp
pacted, a stability test similar to the Hubbard-Field
Stability Test as described in 1925 Proceedings of
American Standard Testing materials was used.

A four inch cylinder and a three and one-half inch
orfice were used in this test. The size of the orfice is
constructed of such size that the maximum.load developed
would be the same as though a 2 or 6 inch mold were used.
The test cylinders were made by compressing the asphaltic
mixtures at room temperature under a load of 3000 pounds
per square inch. The density of the compacted material was
determined by weighing the compacted cylinder and dividing
by the volume. Two cylinders of each material were used.

Cylinder Number 1.
Weight VOlume Density

Bitumals 4.05 lbs. 49.4 cu.in.l42 lbs./cu.ft.
R. C. 6 2 4.12 " 51.7 " 138 "
M. C.x- 3 3.90 " 45.1 " 149 n
S. C. - 6A 3.42 " 43.5 " 136 "

-13-

Cylinder Number 2.

Weight Volume Density

Bitumals 4.06 lbs. 51.2 cu.in.137 lbs./cu.ft.
R. c. - 2 5.74 " 48.2 " 154 7
M. c. - 5 4.54 " 56.8 " 152 n
s. c. - 6A 5.72 n 46.2 n 159 n

Density : (Wei ht) 1728 8 (4.05) (1728) : 142 lbs/cu.ft.
Volume (49 4)

The molded cylinder was placed in an oven and heated
to 1400 F., which represents the maximum temperature the
mixture is like to attain during service conditions. The
molded cylinder was taken from the oven, placed in a mold
which had also been heated. A load was applied to force the
mixture thru the orfice.

The load was then applied on an Olsen Universal Beam
balance sheer test machine. Diagrams of the mix in mold
before and after loading are shown in plate IV. The results

for the four materials were:

(1) (2) Average
Bitumals 3020 3060 3040 pounds.
R.C.-2 3072 3065 3068.5 pounds.
M.C.-3 3325 3375 3350 pounds.
S.C-6A 2500 2300 2400 pounds.

The increase of stability for M.C.-3 was due to the
fact that this was the last sample run. In repeated for
the R.C.-2 it is found that with another week's curing, the

stability had increased to 3475 pounds. This test was run

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two days after the M.C.-3 test was completed.

Now that the laboratory procedure and results are
finished, the method of handling the material in the field
will be explained. The aSphalt mixing plant is a factory
for turning out bituminous mixtures which will meet the re-
quired specifications. These plants vary in size and oper-
ation as the Job may require.

Since there are four kinds of material used in the pre-
liminary part of this paper, it will be hard to get one plant
to use all of these materials wfhout making a few alterations
each time the type of material is used. The person who has
only'a small amount of bituminous aggregate to place would
he better off to use an emulsion. Here an ordinary concrete
mixer is needed to mix the material and a few wheel barrows
and buckets to proportion the materials on a volume basis.
This method would not be economical where a great deal of
material must be mixed and placed immediately. A large
plant for mixing, or a traveling road mix plant would be
better where a large quantity of material is needed each
day.

With the assumption that a large quantity will be need-
ed each day, a 2000 pound batch portable asphalt plant will
be illustrated here showing the path that the material takes
through the plant. The plant is made up of several parts
which all are worked together such that the maxinum.cap-
acity of each unit can be utilized at all times. The

-16-

aggregate is usually charged into a feeding hepper by a
clam shell power shovel. The feeder regulates the flow
on the cold elevator to the 60 inch by 24 feet drier so
that this will not become overloaded and fail to dry the
material sufficiently. The drying is done because, ex—
cept the emulsion, the oil will not get a good bond be-
tween itself and aggregate. From.the drier the aggregate
is elevated on a 33 feet by 6 inch hot elevator with 14
inch by 7 inch buckets to a 3 feet by 10 feet double deck
R. C. Symons screen,either before or after cooling, on
top of the mixing tower. These screens again separate it
in suitable separates for recombination. These separates
are stored in a hopper from which they are emptied
directly into a 2000 pound batcher by the quick opening,
positive acting out off gates on the bottom of the storage
bins. The total capacity of the storage bin is 10,000
pounds, with three compartments which have steep sides

so the aggregate will not stick in the hopper. The pro-
portioning devices consist of the batcher, connected to
Kron aggregate scales, for the aggregate, and 150 pound
steam.Jacketed asphalt cement bucket. The material from.
the aggregate batcher drops directly into the 2000 pound
steam Jacketed anti-friction pugmill where the asphalt

is added evenly across the length of the mixer. The pug-
mill mixes the aggregate and aSphalt so each particle is

.-17-

completely covered and the mixture shall be Of the same
consistency throughout. This mixture is then dumped out
the bottom of the pug mill through discharge gate into
the vehicle that will carry it to the place of use, or to
the stockpile.

Plates V and VI show schematic diagrams of the flow of

the material through the plant.

A is Feeder K is Pug Mill

B is Cold Elevator L is Oil Storage

C is Drier M'is MOtor for Dryer

D is Hot Elevator N 13 Tool Shed

E is Screen 0 is Office

F is Storage HOpper P is Platform.Scales

G is Batcher Scales Q is Gasoline Clam Bucket
H is Aggregate Scales Shovel

I is ASphalt Bucket ' R is Roadway

J is ASphalt Scales S is Stockpile

Photographs Of the plant are on Plate VII, VIII, and
II. The plant as set up above and illustrated by diagrams
and photographs will produce between 25 and 28 tons of
mixed material per hour. For an eight hour day, the plant
would produce between 200 and 225 tons when Operating on
a two minute cycle. This plant, complete with power, costs
$22,500.

There are two more important parts of equipment that

must be used. They are a crane for loading the aggregate

-18-

 

 

 

 

 

 

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Plate V.
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Plate VII
-21-

 

 

 

 

Plate VIII

 

Plate Ix

-23-

into the feed hOpper, and the platform scales to weigh

the loaded trucks as they leave the plant. The crane and
the scales installed costs approximately $9,500, and

31,200 respectively. The crane would be a 3/4 yard Bay
City machine, and the scales a Motor Truck Scales, capacity
15 tons, with a 22 feet by 9 feet platform.

As a general condition in this part Of the country the
plant would be able to Operate only 5 months of the year,
or only 126 working days in which material can be produced.
Assuming the plant would produce an equal amount Of each
type Of mix, we find that the 27,000 tons of aggregate that
would be used during the year, will be divided up so that
6,750 tons will be used with each Oil.

 

 

: % by :Tons :Tons Oil: Gallons: Cost : Cost
E weight, Eaggregate ErequiredE Of E of E of
E Oil Eused per Eper year rE Oil E 011 :Aggregate
R. c. E 8.66 E 6750” E 585 E140, 500E511, 100 E515, 254
M. C. E 7.93 E 6750 E 535 :128, 500: :510, 180: :313, 234
S. C. E 7.22 E 6750 E 488 :117, 200: :3 8, 700: j$13, 234
Bitumals: 8.12 E 6750 E 548 3131 800E512, 600;_§5 613

TOTAL E$52, 580: $45, 315
The mixing Operation of the plant will add three more
cost factors: labor, heat, and power. The labor will be
constant for all of the materials. The personnel the plant

requres is four laborers taking care of machinery, a super-

-24-

intendent; and a crane Operator. The labor cost would be,
on an average, 350 per day.

For the emulsion, the heating would be nothing, but
would run into a sizeable sum when drying the aggregate for
the other materials. The dryer would cost $10 per day to
operate under average conditions. The power for operation
of the plant would cost approximately 327 per day. The
depreciation of the equipment is usually considered to be
20% of the outlay for equipment, and a 5% value for over-
head. This would be 25% of 354,200 or 38,550.

Summing up all of the outlay of money we have:

Depreciation and Overhead $8,550
Labor 36,350
Operation fuel and power 34,720
Bituminous materials 352,580
Aggregates 345,315
TOTAL COST PER YEAR $117,515.

The cost of producing proportional to the cost of

materials put into them.would be:

 

Bitumals $4.50 per ton $29,025 per year

R. C. - 2 34.40 per ton 329,700 per year

M. C.-:3 34.37 per ton $29,497.50 per year

S. C. - 6A 34.34 per ton #329,295. per year
TOTAL $117,517.50 per year.

Thus, it is shown that the cost of producing the four
mixes will vary from $4.30 to 34.40 per ton.

From.the stability tests it seems reasonable to con-
clude that the M.C.-3 and S.C.-6A would be suitable to
stockpile for a short period of time where they could
lose part of their volatile matter, but not become unwork-
able so that it cannot be easily laid and compacted.

The emulsion is the cheapest and most easily produced,
but has the disadvantage that unless placed and compacted,
the emulsion will break, leaving the hard asphalt mixture.

-96'.

 

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