Analysis of sand asphalt mixtures
Transcript of Analysis of sand asphalt mixtures
Scholars' Mine Scholars' Mine
Masters Theses Student Theses and Dissertations
1966
Analysis of sand asphalt mixtures Analysis of sand asphalt mixtures
Maurice A. Sayegh
Follow this and additional works at: https://scholarsmine.mst.edu/masters_theses
Part of the Civil Engineering Commons
Department: Department:
Recommended Citation Recommended Citation Sayegh, Maurice A., "Analysis of sand asphalt mixtures" (1966). Masters Theses. 5777. https://scholarsmine.mst.edu/masters_theses/5777
This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected].
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•