Scholars' Mine Scholars' Mine

Masters Theses Student Theses and Dissertations

1966

Analysis of sand asphalt mixtures Analysis of sand asphalt mixtures

Maurice A. Sayegh

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Recommended Citation Recommended Citation Sayegh, Maurice A., "Analysis of sand asphalt mixtures" (1966). Masters Theses. 5777. https://scholarsmine.mst.edu/masters_theses/5777

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ANALYSIS OF SAND ASPHALT MIXTURES

BY

MAURICE A. SADGR

A

THESIS

subadtted. to the facult7 ot the

UNIViRSITr OF MISSOORI AT ROLLA

in partial tultil.laent of the requireaents tor tbe

Degree ot

MASTER OF SCIENC& IN CIVIL INGDIDRING

Rolla, Missouri

1966

Apprcwecl bJ

ii

ABSTRACT

The objective or this investigation was to determine the optimum

percent of asphalt which should be added to the sand asphalt mixture.

Also the effects or tiller on the properties or the sand-asphalt

mixture were evaluated.

'Ihe variables in this study were mineral tiller, asphalt cement,

am asphalt content. The sand used in this stud;y was sub-rounded, and

unitorml.y' graded. The asphalt was asphalt cement with two different

penetrations, one of 85-100 penetration grade and the other of

120-150 penetration grade.

Tlu-ee different groups or mixt.ures or sand-asphalt were prepared.

The first group consisted of adding 85-100 penetration asphalt to a

mixture of sand and filler. 'lhe second group consisted ot adding

85-100 penetration asphalt to sa.Di only. The third group consisted of

adding 120-150 penetration asphalt to sand. All mixes were prepared

b7 the Harvard Compaction machine and tested in an unconfined

compression machine.

The ph7sical properties analyzed were compressive strengths, unit

weight and air voids in the mineral aggregate. It was found that an

asphalt content of four percent appears to be an optimum percentage

for the three groups ot mixtures tested. It was found also that

tiller increased the desirable properties or sand-asphalt mixture.

iii

The author wishes to extend his sincere appreciation to his

advisor- Dr. Thomas s. Fry for the suggestion of the research topic

and for his continued guidance and counseling through the preparation

of this thesis.

Thanks are also offered for the assistance given b.T members of

~.he staff of the Civil Engineering Department of the UniTersity ot

Missouri at Rolla.

v

LIST OF FIGURES

Figure Page

1 STRESS-5'ffiAIN RELATIONSHIPS FCR A.C. COO'IENT 3%, GROUP A MIXTURES •••••••••••••••••••••••••••••••••••• 16

2 STRESS-S'IRAIN RELATIONSHIPS FOR A.C. CONTENT 4%, GROUP A MIXTURES ••••••••••••••••••••••••••••••••••• l7

3 S'IRESS-5'ffiAIN RELATIONSHIPS FCR A.C. CONTENT 5%, GROUP A MIXTURES ••••••••••••••••••••••••••••••••••• 18

4 S'lRESS-S'IRAIN RELATIONSHIPS FCR A.C. CONT.ENT 6%, GROUP A MIXTURES ••••••••••••••••••••••••••••••••••• 19

5 STRESS-S'IRAm RELATIONSHIPS FOR A.C. CONTmT 7%, GROUP A MIXTURES ••••••••••••••••••••••••••••••••••• 20

6 STRESS-S'IRAIN RELATIONSHIPS FCR A.C. CONTENT 8%, GROUP A MIXTURES ••••••••••••••••••••••••••••••••••• 21

7 S'lRESS..S'IRAIN RELATIONSHIPS FOR A.C. CON'lENI' 9%, GROUP A MIXTURES ••••••••••••••••••••••••••••••••••• 22

8 AVERAGE STRESS-S 'IRA IN CWVES F<li GROUP A MIXTURES ••• 23

9 S'IRESS-STRAIN RELATIONSHIPS FOR A.C. CONWT 3%, GROUP B MIXTURES ••••••••••••••••••••••••••••••••••• 24

10 S'IRESS-S'IRAIN RELATIONSHIPS FOR A.C. CON'IENT 4%, GROUP B MIXTURES ••••••••••••••••••••••••••••••••••• 25

ll S'IRESS-S'lRAlli RELATIOOSHIPS FCR A.C. CON'IENT 5%, GROUP B MIXTURES ••••••••••••••••••••••••••••••••••• 26

12 STRESS-S'IRAIN RELATIOOSHIPS FCR A.C. CONTENT 7%, GROUP B MIXTURES ••••••••••••••••••••••••••••••••••• 27

STRESS-S'lRAIN RELATIONSHIPS FCR A.C. CON'IENT 9%, GROUP B MIXTURES ••••••••••••••••••••••••••••••••••• 28

14 AVERAGE STRESS-5 'IRA IN CURVES FCR GROUP B MIXTURES ••• 29

15 S'IRESS-STRAIN RELATIONSHIPS FeR A.C. COOTENT 3%, GROUP C MIXTURES ••••••••••••••••••••••••••••••••••• 30

16 STRESS-5'IRAIN RELATIONSHIPS FOR A.C. CONTENT 3 1/-zl,, GROUP C MIXTURES ••••••••••••••••••••••••••••••••••• 31

17

18

19

20

21

22

23

24

25

26

28

29

UST OF FIGURES

STRESS-S'IRAIN RELATIONSHIPS FOR A.C. CONTENT 4%, GROUP C KrXTURES •••••••••••••••••••••••••••••••••••••

S'IRESS-S'IRAIN RELATIONSHIPS FCR A.C. CON'IENT 4 1/2%, GROUP C MIXTURES •••••••••••••••••••••••• •' ••••••••••••

S'IRESS-5'IRAIN RELATIONSHIPS FOR A.C. CONTENT 5%, GROUP C MIXTURES •••••••••••••••••••••••••••••••••••••

AVERAGE STRESS-S'IRAIN CURVES FOO GROUP C MIXTURES ••••

V .M.A.-ASPHALT P:mCENT RELATIONSHIPS, GROUP A MIXTURES.

V .M.A.-ASPHALT PmCENT REU.TIONSHIPS, GROUP B MIXTURES.

V .M.A.-ASPHALT PERCENT RELATIONSHIPS, GROUP C MIXTURES.

DEGREE OF SATURATION - ASPHALT PERCENT RELATIONSHIPS, GROUP C MIXTURES •••••••••••••••••••••••••••••••••••••

DEGREE OF SATURATION - ASPHALT PERCENT RELATIONSHIPS, GROUP A MIXTURES •••••••••••••••••••••••••••••••••••••

DIDREE OF SA 'JURATION - ASPHALT PERCENT RELATIONSHIPS, GROUP B MIXTURES •••••••••••••••••••••••••••••••••••••

COMPRESSIVE S'IRESS :- UNIT WEIGHT RELATIONSHIPS,

v;.

32

33

34

35

36

37

38

38

39

40

GROUP A MIXTURES •••••••••••••••••••••••••••••••••••••• 41

COMPRESSIVE S'IRESS - UNIT WEIGHT RELATIONSHIPS, GROUP B MIXTURES ••••••••••••••••••••••••••••••••••••• 42

COMPRESSIVE S'IRESS - UNIT WEIGHT RELATIONSHIPS, GROUP C MIXTURES ••••••••••••••••••••••••••••••••••••• 42

Table

1

2

4

5

LIST OF TABLES

SIEVE ANALYSIS ••••••••••••••••••••••••••••••••••••••

WEIGHT OF SPECIMENS ••••••••••••••••••••••••••••••••••

SAMPLE OF CALCULATION FOR SPECIMENS CONTAINilo.TG SAND + 6%, 85-100 PENETRATION ASPHALT+ 5% FILLER ••••••••••

RELATIONSHIP BE'IWEEN WEIGHTS, PERCENTAGE OF ASPHALT AND MAXIMUM STRESS IN PSI •••••••••••••••••••••••••••

SAMPLE OF CALCULATIOOS FCR V .M.A. AND DlinREE OF SATURATION ••••••••••••••••••••••••••••••••••••••••••

Page

l4

44

49

47

52

I. IN'IRODUCTION

Sand-asphalt stabilization has been accomplished by the addition

of bituminous material in the proper quantities to sand. (1) In the

stabilization of cohesionless soil with asphalt, the mixture serves a

dual purpose of binding soil particles together to give cohesion to the

mass, and of water-proofing the mixture. {2)

The asphalt-stabilized materials are generally used for:

1. The construction of bases for surface-treated roads with low

traff::..c volume:

2. The construction of bases of main roads having concrete or

bituminous surfacing:

3. The water-proofing of subgrade to preserve its stability. (3)

In the United States there are now more than seven thousand miles

of sand-asphalt stabilized base course and sub-base which have perfo~

ed with varying degrees of success. A considerable amount of sand­

asphalt stabilization has been performed in the Province of Manitoba,

Oanada. (4)

Soil stabilization by the incorporation of admixtures has been

subjected to many research projects, particularly in recent years.

At present, sand-asphalt mixtures are being investigated by practical­

ly all agencies concerned with pavement design and construction. The

extent of investigation ranges from comprehensive reviews of published

literature, through long-term performance studies of existing

facilities, to intensive laboratory research projects on specific

problems associated with the stabilization process.

In addition to the conventional use of sand-asphalt for the

construction of bases and sub-bases tor highways, it is also used tor

2

the construction of rainwater reservoirs. The u.s. Government, Depart­

ment of the Interior, is conducting research in this field, especially

in the area of New Mexico, where the results showed that a rainfall of

six inches or more a year can be stored on a base of sand-asphalt and

used economically for irrigation and water supply purposes.

Until recently, the major portion of work in sand-asphalt

"'tabilization has been of a practical nature to arrive at a set of

empirical design standards and construction procedures suitable for use

in a particular locale. Increased efforts have been made during the

past few years to investigate sand-asphalt stabilization on a more

scientific basis and to provide information on fundamental mechanisms.

Due to the large number or factors which influence the strength

and durability of a sand-bituminous mixture, any single investigation

must necessarily restrict the number of variables as much as possible.

Therefore, in this investigation only one type of sand and a hard

asphalt with two different penetrations were used. . Also, only one

method of mixing and compacting was used throughout the testing program.

The unconfined compression test was used to measure the stress-strain

relationship of the samples. It was chosen tor its simplicity.

With these factors in mind, the purpose of this research is to

investigate the relationship between the percentage of asphalt used and

the compressive strength or the mixture, and to determine the infiuence

or the filler on the strength or the sand-asphalt mixture.

II. REVIEW OF LITmA WRE

A. Case History

In 1957 and 1958 the South Carolina State Highway Department was

concerned with the construction of a four lane, divided highway between

Conway ~nd ~rtle Beach on u.s. Route 501. The base consisted of

10 inches of hot sand-asphalt containing 4.CJI, asphalt-cement. The

sand was dark gray in color due to a high percentage or organic matter

and graded as follows:

Pass No. 10 100%

Pass No. 40 71%

Pass No. 80 13%

Pass No. 200 2%

The base was placed in two 5-inch layers. Although there were no

stability requirements on this project, a mixture made in the labora­

tor,y with soil from the pit with 4% asphalt cement gave 160 lbs.

marshall stability.

'Ibis road has a yearly average ot 5,002 vehicles per day and a

summer average of 9,100 vehicles, and except for considerable rutting

is apparently in good condition. It is believed that the surface

could be covered and brought to a uniform cross-section with a treatment

of 150 pounds per square yard of asphaltic concrete. {5)

B. Stabilization Methods

Asphalt is one ot many types of stabilizing agents. Depending on

the mechanisms of stabilization these stabilizers mBT be subdivided into

· three general groups. ·

'lbe tirat group includes materials which cement the soil particles.

4

These materials, capable of reactions within themselves or with certain

soil constituents in the presence of water, produce strong inter­

particle bonds which can support high intensity loads. Typical

representatives of this group are cements, lime, and more recently

acidic phosphorus compounds.

A second group of stabilizers could be termed the soil moditiera

or conditioners. Lime, calcium, or sodium chlorides, and a number of

surface active materials are typical of this group.

The third group embraces the water-proofing agents. Asphalt,

certain resinous materials, and coal tars are representative of this

group. The stabilizers coat individual soil particles or their agglom­

erates, and thereby prevent or hinder the penetration of water into

the stabilized soil layer.

The role of an asphalt film in stabilizing a soil mass depends

to a great extent on the properties of the soil. In the case of non­

cohesive soils (sands and silts) the asphalt film serves a double pur­

pose in that it water-proofs the soil mass and it binds the soil

particles together producing a cohesive material.

c. Mechanics of Asphalt Stabilization

The most important objective of soil stabilization is the elimina­

tion of the dependency of soil engineering properties on moisture

content. The most obvious way in which the water sensitivity of soils

can be eliminated is to coat the individual soil particles with film

of stable, water-insoluble resinous substance which will prevent water

from reaching the particle surf~es, and/or prevent water from migrating

b,y capillarity into a consolidated porous soil mass. The use of a

resinous material provides additional advantages in that it causes the

5

individual particles to adhere to one another, and thus contributes to

the shear strength of the compacted mass.

Asphalt as a soil stabilizer is, however, limited by certain

physical properties both of the asphalt and of the soil. The three

most important factors limiting its effectiveness as a stabilizer are

believed to be:

1. the difficulty of distributing asphalt uniforml.1' throughout

a material such as clay or fine sand,

2. the inability or asphalt to adhere to wet soil particles, and

3. the sensitivity of the asphalt-soil bond to destruction b;y

water.

To facilitate distribution ot asphalt through soils, and thus to

improve its stabilizing aotion by minimizing the first taotor cited

above, three basic appreches have been followed in practice. The

fiuidity of the asphalt at normal temperatures can be increased by

diluting it with volatile solvent. The viscosity can be decreased b;y

heating or emulsification with water in the presence of an emulsifying

agent. All of these processes yield mobile liquids which can be admixed

with soil more effectively. (4)

D. Stabilization of Sand with Cutback Asphalt

At the present time, cutbacks appear to be the most practical

asphalts for sand stabilization. So-called road oils are equivalent

to cutbacks made with fuel oil. These road oils are usual.ly prepared

as direct residuals from tractional distillation and they are the

lowest cost asphalts.

Medium-curing cutbacks (MC) and rapid-curing cutbacks (RC) seem

to be suitable types of liquid asphalt for soil stabilization. 'l'be

6

choice between (MC) and (RC) depends largely on climate, soil type,

and construction practice. Different grades or cutbacks are designated

from 0-5, depending on the percent solvent contained. MC-0 and RC-0

each contain about 50 percent solvent, and the percentage decreases

to about 18 percent solvent for MC-5 and RC-5. A harder asphalt after

curing contributes to better binding in the co~pacted and cured mix.

'lhe higher grades of RC cutbacks may harden before mixing is

completed; lower grades contain more solvent and cure more slowly.

The choice of grade of MC and RC also depends on mixing conditions;

usually the more solvent, the greater the ease of mixing. Solvents

cost about the same as the asphalt and do not contribute directly to

the final strength because they evaporate during the curing process.

The use of high solvent content cutback asphalts may greatly prolong

the curing time. For these reasons MC-0 and RC-0 are seldom used and

A0-2 or 3 and RC-2 or 3 represent usable products. The final choice

is made on the basis of proper consideration or laboratory test results

on the soil to be used and of the climate conditions prevailing at the

time of construction. (6)

E. Functions of Fillers in Bituminous Mixes

For the purpose of this discussion the term "filler" will be

restricted to that fraction of a mineral aggregate, flour or dust,

present in a bituminous mixture that passes the No. 200 sieve.

A filler can perform several functions in the performance of a

bituminous mixture. One of the functions is that of filling voids in

coarse aggregates. This increases the density, stability, and tough­

ness of a conventional bituminous paving mixture. Another is the crea­

ticm of asphalt mixes in 'Which the tiller particles of dust either are

7

individually coated with asphalt or are incorporated into the asphalt

mixture mechanically in the form of a collodial suspension. The effect

of fillers in a conventional-type mix is quite pronounced.

Excessive quantities of tiller tend to increase stability, brittleness,

and susceptibility to cracking. Deficiency of tiller tends to

. increase the void content, lower stability and soften the mix.

Although there has been much theorizing, there has been a lack of

study and literature pertaining to the actual behavior and specific

functions of tillers of various sizes, shapes, and sources, mineral

composition, and their effect on the paving mixture. Unquestionably

all of these factors have some effect on the functioning, behavior, and

effects of a filler.

Two fundamental theories, based on the results of studies, obser­

vations, and experience, have emerged regarding the fUnctions of

fillers in bituminous mixes. One of these theories referred to herein

as the filler theory, postulates that the filler serves to till voids

in the mineral aggregates and thereby creates a denser mix. The other

theory, referred to as the mastic theory, proposes that the filler and

asphalt combine to form a mastic which acts to fill voids and also

bind aggregate particles together into a dense mass.

'Ibe filler theory presumes that each particle of the tiller is

individually coated with asphalt and that coated particles, either

discrete or attached to ~ aggregate particle, serve to fill the voids

in the aggregate. By virtue of such filling of voids, llixes of higher

stability and density can be attained.

Studies and tests have verified the fact that increasing quantities

of tiller tend to increase the stability and density ot the mix.

There is however, a limit to the beneficial effects of increasing

filler content. Fillers may function and behave in many different

ways depending on mixing procedure and the properties of the filler

used in preparing the mix. In mixes prepared in the conventional

manner, fillers serve predominantly to fill voids. (7)

F. Hot Mixed Sand-Asphalt

8

From a practical viewpoint, hot mix stabilization of sand is

seldom practiced; however, the laboratory work in this area is consid­

ered desirable as a basis for strength comparisons. The use of hot

mix methods appeared to work very well to distribute the asphalt in

the preparation of laboratory specimens, but the resultant strength

values were quite low. ( 2)

So far as the writer has been able to ascertain, no work has been

done to study the effect of using hard asphalt cement with 85-100 pene­

tration grade in the laboratory.

9

III. PROCEDURE AND RESULTS

A. General

The primary objectives of this investigation or sand-asphalt design

were the following:

1. To determine optimum percentage or asphalt with 85-100 pene­

tration, 'When added to sand and filler.

2. To determine the optimum percentage or asphalt with 85-100

penetration when added to sand only.

3. To determine the optimwa percentage or asphalt with 120-150

penetration when added to sand only.

The variables in this investigation were asphalt content, asphalt

penetration and filler.

B. Material

1~ Soil - The soil selected for t~~ proj~ct\was tine riYer sand ( \ 'Yl o X-l(\ J ~

obtained from a sand pit located at Pacific, MissoU.ri. 'lhe angularity

of this material varied from sub-round to sub-angular. Table I contains

a sum.-na.ry of the grain size distribution of this material. A standard

specific gravity test indicated that the average specific gravity ot

the solid constituents is 2.68.

2. Asphalt - Asphalt having two penetrations were used in this

investigation. 'Ihe one with an 85-100 penetration was obtained from

American Bitumuls and Asphalt Company in San Francisco, California,

and one with 120-150 penetration was obtained .from Chevron Asphalt

Company in Cincinnati, Cl'lio.

3. Filler - Fly ash with a gradation having 100% passing the No.

200 Sieve was used as filler. It was obtained from Walter N. Handy

COIIlp811Y, Inc. , Springfield, Missouri. The specific gravi t;y ot this

fine grained material was found to be 2.60.

C. lfAuipment

10

1. A Harvard Compaction machine was used for preparing the samples.

'Ihe mold size was 1.312 inches inside diameter b;y 2.816 inches high.

The volume of the mold was l/454 cubic teet • .

2. An electric oven was used for the heating of the sand. A

hot plate was used both for melting the asphalt and keeping the sand

asphalt mixture within the desirable temperature range during specimen

preparation.

3. An unconfined compression apparatus with a modification for

temperature control during testing vas used tor the testing ot the

specimens.

D. Preparation of Specimens

1. ~e sand was heated in the electric oven for 90 minutes at a

temperature ot 2500f. 'lhe required amount of oven dried sand was then

deterained on the basis of 1000 gm. total weight of mixture.

The asphalt was heated on the hot plate until it softened, then

the required aount of asphalt was added to the sand. The mixture was

placed on the hot. plate and mixed by hand thorough~ for three to

· tour minutes.

2. 'Ihe temperature of the batch was kept between 230° - 250°F

during the compaction of the rive specimens. The temperature had. to

be caref\1~ watched because of the volatile nature of the asphalt.

'lbe aold wu pre-heated on the hot plate before the caapaction.

Unitora static pressure was applied to each ot the three l.qers ot the

11

specimen. The total pressure applied to the specimen was 115 lb/in •

Arter compaction both the specimen and the mold were cooled for a

period of 12-15 minutes, and then the specimen was ext;racted care.f'ul.l7

from the mold and cured tor a minimum of 24 hours before testing.

3. 'Ihe specimens were weighed and. the average weight of each

group was determined as shown in Table 2.

E. 'tYPes of Mixtures

By using the previous , method of mixing and molding, three differ­

ent sand-asphalt mixtures were prepared at several different asphalt

percentages. The first series involved the preparation of five speci­

mens for each .of seven different percentage of 85-100 penetration

asphalt. The percentages used were 3, 4, 5, 6, 7, S, and 9 percent

asphalt. Five percent filler (b;y weight of the total mix) was used for

this group of tests.

The second series of mixes inYolved the preparation of five speci­

mens tor each of five different percentages or the 85-100 penetration

asphalt with no mineral tiller. The asphalt percentages used were 3,

4, 5, 7, and 9 percent.

The third series of tests were performed on specimens having

five different percentages of 120-150 penetration asphalt without

mineral filler. The asphalt percentages used were 3, 3 1/2, 4, 4 1/2,

and 5 percent.

An attempt was made to use 200-250 penetration asphalt. The

asphalt in this case was thick viscous liquid 1 using it in the mixture

didn't contribute to the strength of the particles or sand, consequent-

11' no adequate stress-strain curves were developed.

F. Testing Procedure

All specimens were immersed in a water bath for a minimum of 30

minutes before testing. The temperature or the water was kept within

the range of 21.2oc to 21.soc.

12

A standard unconfined compression apparatus modified tor tempera-

ture control was used for testing. The sample was immersed in water

during the testing by inserting the specimen into a hollow water

filled cylinder made from Plexiglas. A Plexiglas compression block

was · placed over the steel compression disc or the machine to keep the

steel from being immersed in the water during the testing. It was

felt that the Plexiglas used in this manner would minimize any tempera-

t ure change in the water surrounding the sample. A thermometer was

kept in the water to detect &nJ temperature change. The temperature

of the bath was kept within the range of 21.2°C to 21.8°0 during the

test period. 'nle load was applied at a constant rate of 0.032 inches

per minute. '!be load applied to the specimen was measured b7 means

ot a proving ring haTing a capacity of 500 pounds. An extensionometer

was attached to the JDachine tar reading the sample deformation.

G. Results

1. Loads tor unconfined compression test samples were taken trom

calibration curves prepared tor the 500 pound proving ring.

2. An area correction table was prepared and the area determined

from the initial diameter and unit strain. This assumed a deformation

at a constant TolU118, that is:

A • Ao 1 -4i

where: A • Final area

Ao • Initial area

( • Unit Strain

A sample calculation is shown in Table 3. 1he relationship between

weights, percentage ot asphalt and strength of specimens in PSI is

shown in Table 4.

Thermo-control precaution• were t&k:en onl.7 a!'tier ~ .tailur•s

13

to get satisfactory results. Prior to the thermo-control precautions,

the same group of specimens prepared trom the same batch would give a

very wide range of stress values. An investiga tim was made ot these

failures and two !actors were suspected as ·causes. 'lbe first factor

was that by leaving the batch on the hot plate for a period ot time

during the compaction or specimens, the temperature of the mixture

became Dllch higher at the end ot the period than it was at the begin­

ning• This caused more volatile materials to leave the asphalt and

resulted in the hardening of the asphalt which in turn gave higher

results for the stress-strain relationship for specimens compacted at

the end of the period. 'Ibis was indicated. b7 the testing of the

labeled specimens. The difficulty seemed to be minimized by controling

the temperature of the batch, and by shortening the period of compaction.

'lhe second factor was the change of room temperature during the

testing of the specimens. No matter how small the change, some

variations in the results of stress-strain relationships were noted.

'lhis · second reason was made more evident by the satisfactory results

obtained after the use of the water bath and the procedure or testing

the sample While it was immersed in water.

In-spite or all the previous precautima, some specimens in some

groapa showed rather vide ditferencea ill results ancl as a result were

1.4

eliminated from the analysis of the data.

CUrves were plotted for each group of specimens as shown in Fig. 1

through 20. Part (a) of each figure is a plot of the stress-strain

data for the individual specimens. Part (b) of each figure represents

an average of the curves which are shown in Part (a) of the figure.

The averaging of the curves was accomplished by calculating

Youngs Modulus (E1) for the elastic (initial) portion of each curve.

The average (E1) was calculated and the inclination of the initial

portion of the stress-strain curve was calculated or measured and

drawn as shown in part {b) of each figure.

An imaginary tangent was drawn r or each linear part of the curve

in part (a) of the figure until it intersected the strain axis. This

point of intersection was then considered as the origin point for that

curve, and all of the other calculations were altered to fit the

corrected curve.

Three other points were chosen on the strain axis. One of these

points involved the determination of the average peak stress and the

average strain at which this stress occurred. The other two points

were concerned with the average stress that occurred at a given strain.

'lhe angle and the three computed points were plotted in part {b)

of the figures, then a smooth curve was drawn to the angle and the

three points.

Table 1. Sieve Ana.lysis

Sieve Size % Passing

30 99.30

50 40.10

100 3.76

200 0.58

APP»JDIX I

Figures 1 throu~ 29

15

10

H8

~ • Wl6

G')

b Cll4

2

0

10

H8 &:

2

0

A.C. Content .3% A.C. Penetration 85-100 Filler Content 5%

4

Strain,Percent Figure la. Stress-strain Relationship

c, 0

Cz C:J c3 > c5 L:J

E i = 8.74 PSI I o /

6... = 6548

2 3 4 Strain,Percent

Figure lb. Average Stress-strain Curve

16

5

5

0

10

H 8 ~ .. ~ 6 Cl)

::! ..., (f) 4

2

A. C. Content 4% A.c. Penetration 85-100 Filler Content 5%

Strain,Percent Figure 2&. Stess-Strain Relationships

C1 0

c2 0 c3 D=> C4 =

Ei = 6. 7. PSI 0 ,

L = ss 4s

Strain,Percent Figure 2b. AYerage Stress-Strain Curve

17

5

18

14 -T .-,---12

10

H

~ 8

.. fl) fl) Q) 6 A.c. Content 5% c2 Q) ...

of) A.C. Penetration 85-100 c3 ~ {/)

Filler Content 5% 4 C4 =

c5 8 2

Strain, Percent Figure Ja. Stress-strain Relationships

12

10

H Q

~ .. 6 en Ei = 7.7 8 PSI It) Q) ... 0 " ~ '- = 62 9 4

2

0 2 3 4 5 St.rain,Percent

Figure )b. Average Stress-strain Curve

H C/) ~

10

.. D') 6 D') (I) J..

~ 4

2

A.c. Content 6% A.c. Penetration 85-100 Filler Content 5%

Strain,Percent

c, 0

C2 <0 c 3 l!>-­C4 cz::~

C5 8

Figure 4a. Stress-strain Relationships

Ei = 4.96 P S l () "' L. = 51 10

o~-----+---'----11'-- __ l_.___,l.___ __ l. __ __._ __ ..__ _ _..._---'

0 2 3 4 5 Strain,Percent

Figure 4b. AYerage Stress-strain CUrve

19

12

10

H 8 ~

2

0

A.c. Content 7% A.C. Penetration 85-100 Filler Content 5%

Strain,Percent Figure Sa, Stress-strain Relationships

Ei =5.28 PSI 0 ,

L = s2 so

2 3 4 Strain,Percent

Figure 5b. Average Stress-strain Curve

20

5

14

12

10

1-f 8~ ~ .. I Cf) Cf)

6 «<) Joe +) A. c. Content S% c2 Q) Cl)

4 A.C. Penetration 85-100 C3 })::>-Filler Content 5%

C5 G 2

0 ' V2 2 2 ';2 3 3 lf2 4

Strain Percent Figure 6a.. Stress~train Relationships

12 ·~--r----r---~---r--.,.----r--.,---- 1

1-f 8 ~

2

Ei=5.23PSJ

L 0 /

=5236

21

I !

I ..... i !

i I

I

j

5

I I

L---+---'---~--~----L---·---l ~---A.---" 0 2 3 4

Figure 6b. Strain1Percent Average Stress-strain Curve

12

10

8

10

H 8 (/) p.. .. "' 6 en (I) ... ~

4

2

A.c. Content 9% A.C. Penetration 85-100 Filler Content 5%

Strain,Percent

4

Figure 7a. Stress-strain Relationships

Cr

c2 C3 c4

E i = 6.6 0 0

(!)

(2) CJ::l

G J

~_j 41/2 5

PSI /

'- = 58 48

2 3 4 5 Strain,Percent

Figure 7b. Average Stress-Strain Curve

23

14

12

10

H 8 (() A.. A.c. Content, 3% ~ ..

4% (/) 6 A.C. Content <::) fl)

(I)

J A.c. Content 5% [!:> ~

~ A.C. Content 6% A.c. Content 7% A.C. Content 8%

2. A.C. Content 9% ; ,· ' ... '

0 2 3 5

Strain Percent Figure 8. Average Stress-Strain Curves for Group A Mixtures

H {!) ll..

8~ I '

0

2

0

A.C. Content 3% A.C. Penetration 85-100 Filler Content 0%

Strain,Perccnt Figure 9a. Stress-Strain Relationships

Ei= 5.2 3 0 /

L = s2 36

2 3 4 Strain,Pereent

Figure 9b. Average Stress-Strain Curve

5

...

5

H (/) A.. .. ~') l!j (j) ;.. ..., (/)

H U) A.. .. Ill Ill II) ... ...,

Cl)

12

IC;_ I I I

' 8-

s~

4L A.C. Content 4% A.C. Penetration 85-100 Filler Content O%

~~-+----~----~'----~---- I I I I I I lf2 2 2 1;2 3 3 112 4 4 1/2 0

Strain,Percent Figure lOa. Stress-Strain Relationships

12

10 Ei = 3.91 PSI 0 /

8 '- = 4 4 20

6

4

2

Strain,Percent Yigure lOb. Average Stress-Strain Curves

25

5

12

10

H 8

~ .. It) co 6 CD ~

~ 4

2

H a ~ .. It) 6 Cl) Q) ... ~

4

2

A.C. Content 5% Penetration 85-100 Filler Content 0%

Q)

2 ~2 Strain1Percent

C1 0

c2 <::)

C3 ~

Figure lla. Stress-strain Relationships

Ei = 4.11 PSI 0 /

L = 4 s 4s

2 3 Strain,Percent

Figure lla. Average Stress-strain Curve

26

12

10

H 8 l2 .. Cl)

6 8)

f A.C. Content 7% c2 ~ .+) Cll A.C. Penetration 85-100

C4 ~ 4 Filler Content 0% C3 })>

2

0 1'2 I 112 2 2 112 3 4 5 Strain,Percent

Figure 12&. Streas-straiD Relationships

12

10

H 8 Cll ~ .. en 6 • Ill E1= 6.11 PSI Cl) ... 0 / ~ L = 5s 5o 4

2

Strain,Percent. Figure l2b. AYerage Stress-strain Cune

H

~ .. ~') en <U J..

+J (/)

141 12 L

i IOL

I

4

2

0

14

12

101 8

6-

4

2

A.C. Content 9% A.C. Penetration 85-100 Filler Content 0%

2 21f2 3 4 Strain,Percent

C1 0

c 2 (?)

C3 })> C4~

C5 8

Figure lJa. Stress-strain Relationships

Ei = 8·46 PSI 0 /

L = 64 42

28

5

10 r I

H i. l2 e L

0

Figure 14.

29

···-~

5

H U) A. .. II) O'l 1\) ~ ~ til

H

~ .. It) O'l Q) ~ ~ til

12 [

10 .

8~ f

t 4:-

2

12

10

6

G~ I

4L 2

A.C. Contont 3% A.C. Penetration 120-150 Filler Content O%

Strain, Percent Figure 15a. Stress-strain Relationships

c,e C ~

2 c4r::3.:=

Csl!J

Ei=2.67P.S.I. L 0 /

=3335

w:....__.....,._ _ ___,.__ _ _ l _ _ _ J __ _____ L___ I

2 3 4 Strain ,Percent

0

Figure 15b. Average Stress-Strain Curve

30

5

5

10

I

2

8

2

0

A.C. Content 3 1/2% A.C. Penetration 120-150 Filler Content 0%

21/2 Strain,Percent

Figure 16a. Stress-strain Relationship

E i = 3.82 P.S.I.

() /

= 4340

2 3 Strain1Percent

Figure l6b. Average Stress-strain Curve

31

5

10-

I I

a!­.... ! 1:1) l

""' I r.ll ... 6 ,-l/) .

cu .... I

..., 'L (,/) 4, ~

~

)

21--•

0

2

A.c. Content 4% A.C. Penetration 120-150 Filler Co~tent O%

1 v2 2 2 v2 3 3 1;2 4 4 v2 Strain,Percent

Figure l?a. Stress-strain Relationships

5

E i = 4 P. S.l. 0 L = 45

2 3 4 Strain,Percent

Figure 17b. Average Stress-strain Curve

32

0

A.c. Content 4 1/2% A.C. Penetration 120-150 Filler Content O%

~2 1 ~2 2 2 y2 '3 3 ~2 4 4 v2 Strain, Percent

Figure l.Sa. Stress-strain Relationship

12 ..----,.-----.--..,.----,---.,----,--- 1---r-·--···,--~--

10

H a.

&: ffJ .. 6 ffJ

f ~

4-

2

Ei= 3.13 P.S.I. 0 /

L. = 386

2 '3 Strain,Percent

Figure 18b. Average Stress~train CUrve

33

2

2

A.C. Content 5% A.C. Penetration 120-150 Filler Content 0%

Joooi!:::'--::~,.. __ ,... __ -:1---~---~----L _ __ J __ L __ J _ _. I y2 2 2 Y2 3 - 3 Y2 4 4 Y2 5 0

Strain,Percent Figure 19a. Stress-strain Relationship

0 /

'- = 30 45

0 2 3 4 5 Strain,Percent

Figure -19b. Average Stress-strain Curve

34

H

~ .. (/) t") Q) ... ~ Cl)

12

' IOI

8

6~ ' i

I

41 21

'

ll # I

0 ''2 Figure 20.

A.C. Content 3% 0 A.c. Content 3 1/2.% ~ A.c. Content 4% D=>

A. c. Content 4 l/2% t=!:1

A•c. Content 5% X

I I I I I I

I lf2 2 2 112 3 3 112 4 4 Y2 5 Strain 1Percent

Average Stress-Strain Curves For Group C Mixtures

35

36

34

32

~ Q) 30 f G)

p....

• 28 < • X • ~ 26

24

22 2 1--------'------4------J.~--- .. ------ .. ---1

5 6 J ____ ----- ____ _j --- _________ J __ ----7 8 9 3 4

Asphalt Percent

Group A Mixtures

Figure 21. V.M.A.-Asphalt Percent Relationship

36

34

32

ti 0 30 ... I. • < 28 • ::.: • p

26

24

22 ~--------~---------1_ 2 3 4

_____ j

5 6

Asphalt Percent

Group B Mixtures

7

Figure 22. V.M.A.-Asphalt Percent Relationships

e 9

38

36r--------------,--------------~------------~--------~

35

g 34

e ~ 33

• < • ~ 32 ~

. 31

30~------------~--------------~--------------J_--------~ 2 3 4 5

Asphalt Percent

Group C Mixtures

Figure 23. V.M.A.-Asphalt Percent Relationships

22

20

s:: 0

•r-1 18 ~ s +>

C'O 16 ell

~ I

0 J Q) 14 Q) I Jot bD I Q)

Q I 12 -i

10 2 3 4 5

Asphalt Percent

Group C Mixtures Figure 24. Saturation-Asphalt, Percent Relaticmships

40 ~--------.---------...----- --,--------r------1---

35

§

"" j 30

., Cl)

~ 0 25 II) ., to t)

c::l

20

15~--------~--------~----------L---------L--------4---------L--------~_J 2 3 4 5 6 7 8 9

Asphalt Percent

Group A Mixtures

Figure 25. Degree of Saturation-Asphalt Percent Relationships

fi ...-4

11 ::1 ~ Cf)

~ 0 ., ., to .,

Q

40~--------~--------~--------,---------~~--------~--------~--------~-

35

30

2l 20

15

10~--------~--------~~--------~---------~----------~--------L---------~~ 2 3 4 5 6 1 8 9

Asphalt Percent

Group B Mixtures

Figure 26. Degree of Saturation-Asphalt Percent Relationships ~ 0

r . r--~-

H 12 ~

~ f II ~

! Wl Wl G) ... ~

0

Unit Weight Lb/cu3

Group A Mixtures

Figure 27. Compressive Stress - Unit Weight Relationships

13

12

H

~II .. :5 ~10 S I en ! Q) 9 ,...._

ta~ / 8 I / 7v

6 ~------~----~~------1------~------~------~------~

42

101 102 103 104 105 106 107 10 8 Unit Weight- lb/cu3

Group B Figure 28. Compressive Stress-Unit Weight Relationships

8

H en A.. .. 7 ..c ~ c: Q) 6 J.. ...,

(f.)

Q)

> 5 •rl C'l (/) Q) a. a 0

0

4

3 99 100 101 10? Unit Weight- lbfcu3

103 104

Group C Figure 29. Compressive Stress-Unit Weight Relationships

APPENDIX II

Tabulation of Data

43

Table 2. \'Ieight of Sp::citr:ons

Specimens Consistin: of Sand + Asphalt ~'"ith 85-100 Penetration + 5% Filler

No. of Wt. in gTl'IS. Wt. in gms Wt. in gms. \'lt. in gtjS. \'lt. in gms. Wt. in gm3. Wt. in gms. Specit/Jns With 3% With 4% . With 5% With 6% With 7% With 8% With 9%

Asphalt Asphalt Asphalt Asphalt Asphalt As~:halt Asphalt

1 103.16 104.87 106.72 108.00 ll0.19 ll0.71 ll2.66

2 102.88 104.67 107.27 108.05 109.50 109.66 112.35

3 103.48 104.26 106.ll 107.87 ll0.67 110.95 ll2.95

4 102.80 104.57 106.21 107.72 108.81 110.70 ll2.18

5 103.16 104.~7 106.22 108.72 109.03 ll0_~2!~ 110.J~ Av. Wt. in g[£S. 10,2.10 104.22 106.21 1os.oz 109.64 ll0.21 112.10

Table 2

( Continu.ed)

Specimens Consisting of Sand + Asphalt with 85-100 Penetration

No. of Wt. in gms. Wt. in gms. Wt • in gtr.s. Wt. in gms. Wt. in gms. Specimens .With 3% . With.4% With 5% With 7% With 9%

Asphalt Asphalt Asphalt Asphalt Asph:".lt

1 101.75 101.43 103.48 105.61 107.55

"2 101.93 101.95 103.48 105.00 107.93

3 101.60 102.00 102.93 105.53 106.87

4 101.94 102.40 103.63 105.00 108.34

~ 101.80 102.12 10~.26 10~.6~ 107.72 Av. wt. in~. 101.80 101.28 103.76 102.~2 107.68

Table 2

(Continued)

Specirn:ns Consisting of Sand + Asphalt tdth 120-150 Penetration

No. of Wt. in gms. Wt. in gms. Wt. in gms. Wt. in gma. Wt. in grns. Specimens With .3% With 3 .1/2$ r!ith 4% With 4 1/2% With 5%

Asphalt Asphalt Aepha1t AsJ2ha1t Asphalt

1 99.74 101.33 102.47 102.87 103.29

2 100.53 102.00 102.38 102.00 103.26

J 100.30 101.10 102.15 102.20 103.65

4 101.15 100.70 101.83 102.88 10).61

~ 100.74 101.62 101.62 102.83 10~.~1 Av. Wt. in ~s. 100.49 101.22 102.12 102.~6 . 10.2.46

Table 4

Relationship Between Weights, Percentages of Asphalt and ~~mum Stress in PSI

Specimens Consisting of Sand + Speci~ens Consisting of Sand + Specimens Consisting of Sand + Asphalt 85-100 Penetration+ . A$phalt 85-100 Penetration Asphalt 120-150 Penetration

~~Filler

% Weight Compressive % Weight Compressive % Weight Compressive Asphalt in grns Strength in PSI Asphalt in gms Strength in PSI Asphalt ingms Strength in PSI

3 103.10 9.30 3 101.80 6.75 3 100.49 4.00

4 104.59 10.80 4 101.')8 7.00 3 1/2 101.35 4.80

s 106.51 10.80 5 103.98 8.80 4 102.15 6.40

6 108.07 10.30 -- 4 1/2 102.56 4.30

7 109.64 12.00 7 105.35 9.')0 5 103.46 3.55

8 110.51 n.80 ------9 112.10 12.50 9 107.68 12.80

APPENDIX lit

Sample CalculatiODS

48

Table 3

Sample Calculations For Specimens Containing Sand + 6% 85-100 Penetration Asphalt + 5% Filler

STRAIN S'IRESS No. of . Deformation Strain Per. The .Final Load-Dial Load in Stress In

Specimens In inches Area (in2) Readin~ Pounds PSI

1 0.010 0.356 1.355 2.1 1.57 1.157

0.035 1.242 1.368 8 6.00 4.380

0.055 1.955 1.378 14.5 10.90 7.920

0.075 2.670 1 • .388 16 12.00 8.620

0.095 3.380 1.399 16.8 12.60 9.010

0.115 4.080 1.409 16.6 12.45 8.840

0.125 4.440 1.413 16.2 12.10 8.560

2 0.010 0.356 1 • .355 2.1 1.58 1.165

0.025 0.890 1.362 6.1 4.57 2.350

0.055 . -1~9$5 1 • .378 15.0 ll.25 8.180

0.0'75 2.670 1.388 16.9 12.70 9.160

0.095 ).380 1.399 17.1 12.80 9.160

0.105 3.130 1.403 17.1 12.60 9.130 ~ -.1:)

0.125 . 4~440 . 1.413 16.6 12.45 8.800

Table 3

(Continued)

S'IRAIN SUESS No or Deformation Strain Per. The Final Load-Dial Load-in Stress in

Specimens In Inches Area (in2) Reading Pounds PSI

3 0.010 0.533 1.359 2.9 2.17 1.6o3

0.035 1.242 1.368 8.5 6.37 4.630

0.055 1.955 1.378 15.2 11.40 7.720

0.075 2.670 1.388 18.3 13.70 9.800

0.105 3.730 1.403 19.261 14.-40 10.260

0.125 4.440 1.413 19.0 11.-25 10.080

0.135 4.800 1.418 18.7 14.00 9.890

4 0.010 0.356 1.355 1.9 1.42 1.048

0.030 1.065 1.365 7.5 5.62 4.120

0.050 1.775 1.375 16.0 12.00 8.730

0.070 2.430 1.385 18.2 13.65 10.750

0.090 3.200 1.396 20.9 15.70 11.240

o.uo 3.910 1.405 20.9 15.45 ll.200

0.130 4.620 1.418 20.6 15.45 10.900 \1\ 0

Table 3

{Continued)

STRAIN S'IRESS llo of Defor-mtion Strain Per. The Final Load-Dial Load In Stress In

Specimens In Inches Area (in2) Readin~ Pounds PSI

5 0.010 0.356 1.355 1.8 1.35 0.996

0.030 1.065 1.365 6.5 4.87 3.560

0.050 1.775 1.375 14.0 10.50 7.640

0.070 2.430 1.385 18.5 13.90 10.030

0.100 ).560 1.400 20.1 15.75 ll.240

0.120 4.270 1.410 20.0 15 10.640

0.130 4.620 1.418 19.9 14.92 10.530

Table 5

Sanple or Calculations

V.M.A. and Degree or Saturation

5~ Asphalt Content - Without Filler

Sand specific gravity .. 2.68

Asphalt specific gravity • 1.02

Asphalt content total weight • 5%

Average weight of the aix in the specimen • 103.76 ~·

'lbe volume of the mold • 60. 6 c;J.

Asphalt by weight in the specimen • 103.76 x 0.05 • 5.18 ~·

Sand by weight in the specimen • 103.76 x 0.95 • 98.5 gms.

Asphalt by volume in the specimen =- 5.18 • 5.08 c.:?. 1.02

Sand by volume in the specimen • ~ • 36.75 ~. 2.1)8

Volume of sand + Asphalt • 36.75 + 5.08 • 41.83 c.,;J.

Volume of voids • 60.5 - 41.83 • 18.77 c~.

V .M.A. • ~ X 100 • 31% 6Q.60

Total volume of voids • 60.60 - 36.75 • 23.85

Degree ot saturation • Volume of asphalt x 100 Total volume of voids

• 5.08 X 100 • 21.3% 2).85

52

53

IV. DISCUSSION

A. General

As mentioned previously the variables in this investigation are

asphalt content, type of asphalt cement and mineral filler. Prior to

discussing the effects of the variables on the ability to predict the

physical properties of a mix, it is desirable to evaluate the role of

each of these variables in the sand bituminous mix.

The asphalt cement perto~s a dual role by acting as a cementing

agent, thereby increasing the cohesive properties of the mix, and as

filler by partially filling the voids in the mineral aggregate. The

ndneral filler frequently performs a dual role, but the effect is some­

what less obvious. Filler particles increase the number of inter­

particle contacts thereby increasing the internal friction and some of

the finer particles or mineral filler are in suspension in the asphalt

cement and they either coat the larger particles or have an apprciable

effect on the apparent viscosity of the asphalt. (S)

The results of this study indicate that there is a direct relation­

ship between the physical properties or a design asphalt mixture and

the type and quantity of the asphalt. They also indicate the effects

or the filler on the properties or sand-asphalt mixt,ure. 'lhese

relationships are shown in Figure S, 14, 20, 21, 22, and 23. The

numerical data for these relationships are summarized in Tables 2 and 4.

B. The Effect of Asphalt

A continuous increase occurs in the compressive strength as a

result of increasing the percentage of asphalt ( 85-100 penetration) in

the mixture. 'Ibis is due to the action of the asphalt as a filler

and to the high viacositr or this t7P8 ot asphalt.

54

Asphalt with a 120-150 penetration causes an increase in compres­

sive strength for up to four percent asphalt added. An appreciable

decrease in strength was found for the 4 1/2% and the 5% asphalt in

the mixture. For the three different percentages of asphalt (3%,

3 1/2, and 4%) the asphalt acted as a binder and coater to the

particles of the sand. It gavo the mixture cohesiveness and strength,

and. it filled. portions of the voids between the ·particles. But, with

an increase in · the percentage of this asphalt to 4 1/2 and 5 percent

the low viscosity of this type or asphalt causes a lowering of the

compressive strength. The changes in strength that occur with varying

asphalt content appear to be a fUnction of the thickness of the film

that coats the particles. As the film thickness increases the

relatively low viscosity of the asphalt makes it easier for the sand.

particles to move with respect to each other and as a result the

strength of the mix approaches a lower limiting value which is the

viscosity or the asphalt cement.

c. Tne Effect of Filler

Both the compressive stress and the unit weight of the mixture

are increased due to the dual action of the filler. 'lhe filler in!'6 ·

creases contact between the particles of the sand. and. this results in

more shearing resistance. Also, due to a filling of the voids the

unit \w-eight is increased. 'lbe void ratio decreased due to the use of

filler in the mixture. 'lhe effect ot filler has been demonstrated. in

this investigation by comparing two different groups ot mixtures, one

with tiller and the other without it. The one to which filler was

added yielded higher compressive strengths and higher unit weights.

D. Stress-Strain Relationship

1. Group A Mixtures:

55

Tnis group of mixtures consisted of 85-100 penetration asphalt

added in seven different percentages (3% through 9%) to a mixture ot

sand containing 5 percent filler material.

In Figure 1 through 8, it is shown that by increasing the asphalt

percent in the mixture, a higher ma:x:imum. stress was achieved and the

maximum strain before failure increased simultaneouslf with the in­

crease in stress. The increase in the maximum stress was rather small

for mixtures having asphalt contents ranging from seven to nine per- ·

cent. The 'llaximum stresses for the mixtures containing 4%, 5% and 6%

asphalt were very close to each other too, as shown in Figure 8.

'Ih~ Ei (Young's Modules) for this group did not change directly

with the stress-strain relationship. The highest Ei value in this

group was for the mixture which contained 3% asphalt.

2. Group B Mixtures:

This grat'P of mixtures consisted of 85-100 penetration asphalt

added to sand without filler in five different percentages (3, 4, 5,

an<i 9). The increase in the percent of asphalt added was always

accompanied by an increase in the maximum stress and maximum strain

be.f'ore failure as shown in Figure 9 through 14.

The (Ei) was increased simultaneously with the increase in the

percent of asphalt from 4% through 9%.

3. Group C Mixtures:

This group consisted of asphalt having a 120-150 penetration

range added to the sand in five different percents (3, 3 1/2, 4, 4 1/2,

and 5). The maxilllllm stress was increased b,y increasing the percent of

56

of asphalt added, up to the 4% where it began to decrease with an

increase in asphalt content. The relationships are shown in Figure 15

through 20. The strain corresponding to the ma:.ximum stress was in­

creased or decreased according to the increase or decrease in maximum

stress.

'!he (E1) of this group was higher for the mixture which yielded

higher maximum stress and lower for the one which Jielded lower

maximm stress.

E.· Relationship Between Asphalt Content and Unit Weight

'lhe unit weight of the mixture in each ot thea groups was in­

creased with an increase in the percent or asphalt added {see Table 4).

'lhis is because the asphalt acted as a filler tor a portion ot the Yoids

in the mixture. Figures 21 through 23 indicate that by increasing the

percent ot asphalt, the V.M.A. (the voids in mineral aggregate) were

decreased continuously. By increasing the percent or asphalt added

to the mixture, the degree or saturation for the v~ds was increased

as shown in Figure 24 through 26.

F. Unit Weight -Compressive Stren~h Relationship

Tho unit weight - compressi't'e strength relationship followed the

same trends as the relationship between percentage of asphalt and

stress. 'Ibis is shown in Table 4 and Figures 'Z7 t~rough 29. For the

mixes ot both groups A and B there was a general increase in the

compressive strength when the unit weight of the mixture was increased.

For group C the unit weight-strength relationship was non-linear as

1nclicated in Figure 29.

G. E-valuation of Results

1. Group A:

57

For this group the maximum stress-strain, and unit weight were

increased simultaneously with the increased percent of asphalt added,

and the V.M.A. decreased at the same time. This resulted from the

asphalt working ~s an adhesive material and binding the sand particles

together and providing more cohesiveness to the mix. Also, the

asphalt acted as a filler for a portion of the voids, this was

especially true in mixtures where a rather high percent of asphalt

was used. This conclusion is supported by the curves shown in both

Figures 21 and 25. In Figure 21, the curve which shows the V .M.A. and

asphalt content relationship started taking a straight line shape

between the 5% and 7% asphalt contained. The degree of saturation

and asphalt contained followed a straight line relationship above the

5% asphalt contained as shown in Figure 25. Because of the high

V.M.A. of the mixture in this investigation, the straight line of the

curves in the previous two figures indicated that the asphalt contain­

ed in excess of 5% had been acting as filler. From this, it can be

concluded that in a mixture in which the V .M.A. is low, a condition

l<1"lich could be brought about by increasing the compaction effort and

using well graded sand, the asphalt in excess of 5% will not be needed.

By referring to Figure 8, it can be seen that no increase in maximum

stress resulted when the percentage of asphalt was increased from 4 to

5. From the previous results and discussion, the 4% asphalt content

could be considered as the optimum percentage of asphalt used in this

group if the V.M.A. is kept within the desirable limits.

2. Group B:

In this group of mixtures, the maxi n1m stress, the maxi m11m strain

at failure, and the unit weight were increased by increasing the

asphalt content.

of asphalt added.

The V.M.A. was decreased by increasing the percent

The asphalt fUnctioned the same way as it did for

58

group A. Figure 22 shows the relationship between V .H. A. was linear

for the range of asphalt contents used. This supports the previous

assur.1ption that the asphalt has functioned as a filler. Further

evidence of this fact is indicated by the degree of saturation as

shown in Figure 26.

In this group, the maximum stress increased noticeably when the

asphalt content was increased from 4% to 5%. The reason for this

·' .ncrease can be related to the absence of filler in this group. The

same statement made concerning the desirable percentage of asphalt

added to the group A could be made about group B. That is if the

V .l-I.A. were kept low, and within desirable limits, the 4 percent

asphalt content appears to be the optimum value.

3. Group C:

For this group, the unit weight and V.M.A. acted the same as in

both group A and C. However, the maximum stress and maximum strain at

failure increased with asphalt contents up to 4% then it decreased

thereafter as shown in Table 4 and Figure 29. Even though the asphalt

acted as a filler for a portion of voids, the comparatively low

viscosity of asphalt used in this group made it easier for the

particles of sand to slide on each other when the asphalt content was

increased beyond the optimum value.

For this group the optimum percentage of asphalt is in the order

of 4% as shown in both Figures 20 and 29.

59

CONCWSICliS

On the basis or the data accumulated during tbe experiments and

the anal.;rsis thereof, certain trends for the beharlor ot sand-asphalt

mixtures have been aentioned. which lead to the tollowi.n! tentatift

coaclusions.

1. Filler has a definite beneficial effect on the physical

properties or sand-asphalt Jlixes. 'lhe use ot 5% filler in the

mixtures increased the unit wight, •xhmlll stress, and decreased

the VMA.

2. A continuous increase in the ux111111a compressi Ye stress result­

ed traa an increase in the percentage or 85-100 penetration asphalt

used in a lldx. In the case ot 120-150 penetration asphalt. the

increase in the compressive stress continued wi~h increasing the

percentage or asphalt to 4% decreased thereafter.

3. '!he unit weight or the m.ixt.ure in each or the three groups

waa increased with an increase in the percent asphalt added.

4. At asphalt contents above 5%, a porti<lll ot the as}ilalt acted

as a filler for part ot the total Toid TolUID8 • .

5. There. appears to be no direct relation between uncontined

compressive stress and the Youngs MOdulus of the mixes ot group A.

6. In general for the groups B and c, the maxiiDWil compreaaift

stress increased and decreased auccessiYel.;r b.r t.he increase ar

decrease in the IO\DlgS Modulus or the uterial.a ot that group.

BIBLIOORAPHY

1. WEA~, H. c. (1937) Sand-Bituminous Stabilization, Highwa7 Research Board, Vol. 17, P. _521.

2. ANDERSON, JC. O., HASS, R. C. G., and LAPLANTE, A. D., 1965,

60

Triaxial Shear Strength Characteristics or Some Sand-Asphalt Mixtures, Highwa)- Research Record, Jlo. 91.

3. ABDEL-HADY, M. and HERRIN, M. (1965), Rheological Properties ot Compacted Soil-Asphalt Mixtures, Highwa7 Research Record, No. 91.

4. PmNELL, D. G., (1962), Structural Comparison or a Sand-Asphalt with a Soil Cement. Unpubl. M. sc. Thesis, Univ. ot Alberta.

5. ANDRDiS, JR., C. E., (1965), 'lhe Histor7 ot Sand-Asphalt in South · Carolina, Paper presented at South em Association of

State Highwa7 Officials, Charleston,, South Carolina.

6. KA'ITI, R. K., DAVIDSON, D. T. and SHtJl.m, J. B., Water in Cut­Back Asphalt Stabilization ot Soil, Hig~ Reaearch Record, No. 241.

7. LADIS H. CSANn, Functions ot Fillers in Bituminous Mixes, Highwa7 Research Record, No. 329.

8. KALLAS, B. F., PUZINAUSKAS, V. P., and JCNIIDER, H. C., (1962). Mineral Fillers in Asphalt Paring Mixture, Highwq Research Board Bulletill 329, P. lS.

VITA

Maurice Abdulla Sayegh was born on JlUle 8, 1938 at Hosul, Iraq.

He attended primary school in Mosul.i then the Intermediate and High

School in Baghdad, graduating from Central High School in June 1956.

He attended the University of Baghdad tor three years and graduated

with a Deploma degree in Cirll Engineering in June 1959.

He served for three years and eight months in the Iraqi Arrsrr

as a reserve Lieutenant.

61

In September 1963, he enrolled at the University ot Missouri at

Rolla, Civil Engineering Department, working for a Bachelor ot Science

degree in Civil Engineering which he received in May, 1965.

In summer, 1965 he enrollecl in the Civil Engineering DepartJDeDt

ot the Universit;r ot Missouri at Rolla as a graduate student working

towards the Master of Science degree in Cirll iDgine•rihs•