International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online), Volume 5, Issue 7, July (2014), pp. 176-187 © IAEME
176
PERFORMANCE EVALUATION OF ASPHALT MIXTURE MODIFIED BY
HYDRATED LIME AND POLYPROPYLENE
Ali A. Alwash Fatimah Fahem Al-Khafaji
Prof. Asst. Lecturer
Babylon University Babylon University
ABSTRACT
Scientists and engineers are constantly trying to improve the performance of asphalt
mixtures. Additives have been used for improving performance of HMA pavements to various
distress (permanent deformation, moisture damage, and fatigue or low-temperature cracks).
The major objective of this research is to evaluate the mixing some additives on performance
of flexible pavement by using asphalt from Al- Daurah refinery with two locally additive. That
additives represented by hydrated lime and polypropylene. Hot mix asphalt specimens have been
prepared with aggregate, nominal maximum size (25) mm (base course) and (19) mm (binder course)
. One type of mineral fillers has been used : Portland cement. Percentage of Portland cement has
been used in this work (5%) for base course and (6%) for binder course. Polypropylene has been
used as additive with the percentage (1, 2, 3)% by weight of asphalt .Hydrated lime was used in dry
state with the percentage (1)% by weight of total aggregate as part replacer of the used filler content.
The performance asphalt mixtures are evaluated using Marshall test, index of retained strength test
and indirect tensile strength test. It is concluded that using hydrated lime and polypropylene
modified to asphalt mixtures shown the results of Marshall test and those of indirect tensile test are
increased by (1.3, 1.5) times respectively after compared with control mixtures . While the index of
retained strength test is increased by (1.3) times after compared with control mixtures .The addition
of combination of ( 1% hydrated lime by weight of aggregate , 2% polypropylene by weight of
asphalt) to asphalt mixtures could satisfy the performance requirement of rutting, fatigue cracking
and moisture susceptibility .
Keywords: Hot Mix Asphalt, Additive Combination, Filler Addition, Marshall Test, Index of
Retained Strength Test, Indirect Tensile Strength Test.
INTERNATIONAL JOURNAL OF CIVIL ENGINEERING
AND TECHNOLOGY (IJCIET)
ISSN 0976 – 6308 (Print)
ISSN 0976 – 6316(Online)
Volume 5, Issue 7, July (2014), pp. 176-187
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International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online), Volume 5, Issue 7, July (2014), pp. 176-187 © IAEME
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INTRODUCTION
Any asphalt pavement, when designed and constructed properly, will provide years of
service. Pavements continually undergo various types of stresses that induce minor or large defects
into the pavement. Traffic loading, structural, sub grade movement, weathering, moisture and aging
can cause stresses. These distresses will eventually lead to the pavements failure. The major
disadvantages of asphaltic pavements are it's greatly influence by the environmental changes. In
summer the high temperature can soften the asphalt binder and consequently reduce the stiffness of
the paving mixture leading to rutting. On the other hand in winter the low temperature can stiffen the
asphalt binder and reduce the flexibility of the paving mixture. As a result thermal cracking may
develop. Thus, high temperature stiffness and low temperature flexibility are important properties
that increase the lifetime of pavements.
The binder of such mixes should possess a high softening temperature to reduce sensitivity for
rutting and should have a reasonable penetration value to minimize the chances of cracking.
Modifications of asphalt by the addition of flexible polymers to asphalt binder can significantly
reduce these shortcomings and reduce the frequency of maintenance and provides much longer
service life for maintenance treatments. The addition of polymer polypropylene combined with
minor amounts of hydrated lime to the base asphalt produced modified asphalt mixtures with higher
Marshall stability and flow values, indirect tensile strength and fatigue life values at high.
There are numbers of different additives, which can be introduced directly to the asphalt
cement (AC) as a binder modifier, or can be added to the mixture with the aggregate.
Hydrated lime has shown multifunctional effects in hot-mix asphalt (HMA) mixtures.
Numerous studies have demonstrated that hydrated in asphalt mixtures can reduce pavement rut-
depth because of its distinct stiffening effects, moisture-associated damage by improving the
aggregate-asphalt bonding, and long-term oxidative aging potential. Several experimental studies
have also shown that hydrated lime can reduce asphalt cracking to some extent despite its stiffening
effects because the initial microcracks can be intercepted and deflected by tiny, active lime particles.
Since stiffer mixtures are generally more susceptible to cracking, the crack-resistant
characteristics of hydrated lime might be degraded from certain critical amounts of lime added,
whereas the rut-resistant potential of mixtures can still be enhanced.
Polymers are the most commonly used additives in binder modification. Among polymers, the
plastomers polypropylene (PP) is the most widely used one. It can obviously improve the mechanical
properties of mixtures such as aging, permanent deformation, low temperature cracking, moisture
damage resistance, and so on.
EXPERIMENTAL WORK
• Material used Material used in this study are locally available. They are included coarse and fine
aggregates, mineral filler, asphalt cement and additive.
• Asphalt Cement One penetration grade (40-50) of asphalt cement is used from Daurah refinery. The physical
properties and tests of asphalt cement are presented in table (1).
International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online), Volume 5, Issue 7, July (2014), pp. 176-187 © IAEME
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Table (1): Physical Properties of Asphalt Cement
Tests Units Penetration grade
(40-50)
S.C.R.B
Specification
Penetration (25 0C), 100 gm, 5sec) ASTM D-5 1/10 mm 44 (40-50)
Kinematic Viscosity at 135 0C ASTM-2170 * cst 380 -----
Ductility (25 0C, 5 cm/min) ASTM D-113* cm 104 >100
Flash Point ASTM D-92(Cleveland open cup)* 0C 335 min. 232
Specific Gravity at 25 0C ASTM D-70 * …… 1.03 (1.01-1.05)
(*)Road laboratory of civil engineering Babylon and Daurah refinery
2.1.2 Aggregates The source of the coarse aggregate used is Al- Najaf quarry which is a crushed stone. This
aggregate is widely used in the middle and south areas of Iraq for asphalt pavement. The particles
tend to off white in color with angular surfaces. The fine aggregate is obtained from Karbala quarry.
The fine and coarse aggregate are sieved and recombined in the proper proportions to meet the
gradations required by SCRB specifications.
Routine tests are performed on the aggregate to evaluate their physical properties. The results
together with the specification limits as set by the SCRB are summarized in table (2).
The gradation of aggregate; a nominal maximum size of (25mm) and (19mm) are shown in
table (3). Test results show that the chosen aggregate met the SCRB specifications.
Table (2): Physical Properties of Aggregate
Property ASTM Designation Coarse aggregate Fine aggregate
Bulk specific
gravity
C-127
C-128 2.55 2.64
Apparent specific
gravity
C-127
C-128 2.65 2.67
% water absorption C-127
C-128 0.83 0.65
Abrasion (Los
Angeles) C-131
26 %
Max 30 % ----------
Angularity D-5821 95 % -----------
(*)These tests were accomplished in the transportation laboratory of civil department
engineering in the Babylon University.
International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online), Volume 5, Issue 7, July (2014), pp. 176-187 © IAEME
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Table (3): Asphalt mixture grading for base and binder courses
No.
Sieve size Specification limits
for base course
(SCRB)
Specification limits
for binder course
(SCRB)
Standard
sieves (mm)
English sieves
(in)
1 37.5 1/2
1 100 ------
2 25.0 1 90-100 100
3 19.0 3/4 76-90 90-100
4 12.5 1/2 56-80 70-90
5 9.5 3/8 48-74 56-80
6 4.75 No.4 29-59 35-65
7 2.36 No.8 19-45 23-49
8 300 µm No.50 5-17 5-19
9 75 µm No.200 2-8 3-9
• Mineral Filler In this research, one type of mineral filler has been used: Portland cement. Percentage of
Portland cement has been used in this work (5%) for base course and (6%) for binder course. The
physical properties of filler are presented table (4).
Table (4): Physical properties of the used filler
Property Cement
Specific gravity 3.10
Finness (cm2/gm) 3080
% passing sieve No. 200 96
(*)These tests were accomplished in the transportation and material laboratories of civil engineering
in the Babylon University.
• Additives
• Hydrated lime
Hydrated lime was used in dry state with the percentage (1)% by weight of total aggregate as
part replacer of the used filler content. The physical properties of hydrated lime are presented table
(5).
International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online), Volume 5, Issue 7, July (2014), pp. 176-187 © IAEME
180
Table (5): Physical properties of hydrated lime
Property H. lime
Specific gravity 2.45
Finness (cm2/gm) 3870
% passing sieve No. 200 100
(*)These tests were accomplished in the transportation and material laboratories of civil engineering
in the Babylon University.
• Polypropylene (PP)
It is a white fiber apparent product and is used as a modifier in asphalt concrete, to satisfy the
desire mechanical properties of asphalt pavement. Polypropylene was used in wet state with the
percentages (1,2,3)% by weight of asphalt at bending speed 2620 rpm and temperature of 150 0C and
time of 60 min (Al-Bana, 2009, physical recarch, 2005) and then the mixture of fiber and asphalt
will blend with aggregate. The characteristics of polypropylene are presented in table (6).
Table (6): Characteristic of PP (SCPI,2008)
Virgin Polypropylene Fiber Form
0.91 Specific gravity
Nil Alkali content
Nil Sulfate content
Nil Chloride content
( 18 – 30 ) microns Fiber thickness
(5500 – 7000 ) MPa Young modulus
350 MPa Tensile strength
( 150 – 160 ) 0C Melting point
( 6 – 12 ) mm Fiber length
2.2 Test Methods The test Methods employed in this research are to evaluate the performance of different
mixtures, in which are included Marshall test, indirect tensile test and index of retained strength test.
2.2.1 Marshall Test Standard method of Marshall as in (ASTM D6927-06) specifications was used for compacted
asphalt concrete specimens.
Test specimens were fabricated for a range asphalt contents (3-5.5)% for base course and (4-
6)% for binder course. The optimum asphalt content selected for design is essentially a compromise
value, which meets specified requirements for stability, flow, and voids in total mix (VTM).
International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online), Volume 5, Issue 7, July (2014), pp. 176-187 © IAEME
181
It was found that the optimum asphalt content required was (4.5% for base course and 4.8%
for binder course) Marshal apparatus and compaction apparatus are shown in plate (1). The [SCRB
(2003)] specification of mix design criteria for heavy traffic roads recommends the following values
for base and binder course, as shown in table (7).
Table (7): SCRB Specification of Mix Design
Properties S.C.R.B Specification
Limits for base course
S.C.R.B Specification
Limits for binder course
Marshall stability, KN 5 (minimum) 7 (minimum)
Marshall flow, mm 2 – 4 2 – 4
Air voids, % 3 – 6 3 – 5
Voids filled with asphalt, % 65 – 85 65 – 85
Void in mineral aggregate, % 12 (minimum) 13 (minimum)
Plate (1): Marshall Apparatus and Compaction Apparatus
2.2.2 Indirect Tensile Test (IDT) The indirect tensile test (IDT) as in (ASTM D4123-02) specification was used to measure the
creep compliance and strength of asphalt mixture using indirect tensile loading at intermediate
temperatures. Indirect tensile testing applies a compressive load across the diametrical axis of a
cylindrical specimen.
IDT Strength (Fatigue Cracking Analysis). This test is used to analyze mixtures for fatigue
cracking resistance. For intermediate analysis, use a test temperature 200C or less for fatigue
cracking analyses. Lower the temperature of the environmental chamber to the test temperature with
( ± 0.20C) is achieved, allow each specimen to remain at the test temperature from 3±1 hours prior to
testing. In this test, the specimen is loaded at a constant deformation rate of 2 inch per minute (50
mm per minute) of vertical ram movement. The specimen is loaded until failure – peak load is
measured throughout the test.
International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online), Volume 5, Issue 7, July (2014), pp. 176-187 © IAEME
182
The type of failure recorded may be helped to understand the crack mechanism and to
provide a real comparison between the testes materials.
The dimensions of the sample are 4 inch (101.6 mm) diameter and 2.5 inch (63.5 mm) height
with load to failure along the diametrical plane of the sample.
In the road laboratory of civil engineering, university of Babylon Marshall apparatus is used
to conduct this test by replacement the device head with two metal bracket 0.5 inch (12.5 mm) width,
as shown in plate (2).
Plate (2): Process of Converting Marshall Test to Measure the Indirect Tensile Test
The indirect tensile method is used to develop tensile stresses along the diametric axis of the
test specimen. The horizontal tensile stress at the center of the test specimen is calculated to
determine the indirect tensile strength by doubling the peak load (P) and then dividing it by the
diameter (d) of the sample and the thickness (t) of the sample using the following equation (1).
σ = (2*P)/(π*t*D) ------------------ Eq. (1)
Where:
σ = Tensile strength (Mpa).
P = Peak load (N).
t = Thickness of specimen (mm).
d = Diameter of specimen (mm).
2.2.3 Immersion Compression Test The method is currently designated ASTM D 1075 or AASHTO T 165. Test of index of
retained strength (%), was done for HMA specimen with all the adopted variables. Two groups of
compacted specimens are used in this test method. One group is submerged in water for
conditioning, and the other group is maintained dry. For a 4-inch length specimen. The average
strength of conditioned specimens over that of dry specimens is used as a measure of moisture
sensitivity of the mix. The compression apparatus is shown in Plate (3).
International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
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Plate (3): The setup of compression apparatus (left) and locally fabricated head cross of compression
apparatus (right)
3. RESULTS AND DISCUSSIONS
3.1 Marshall Test
Stability is an important for the asphalt mixture in the base and binder course design. It shows
the ability to resist shoving and rutting under traffic. Almost the stability treated asphalt concrete
mixtures and regardless of additive type and (% of filler combination or addition) is higher than the
control asphalt concrete mixtures.
An air void in the mixture is an important parameter because it permits the properties and
performance of the mixture to be predicated for the service life of the pavement.
• The results of control mixtures agree the Iraqi specification (section R9).
• The best combination was (1% hydrated lime, 2% polypropylene) for stability while other
combination (1% hydrated lime, 1% polypropylene) & (1% hydrated lime, 3% polypropylene)
still agree the Iraqi specification but with lower values.
• The best combination was (1% hydrated lime, 2% polypropylene ) for the percent of air void
value except of percent of air void value of NMAS about 25 mm in mixture which contain
combination of (1% hydrated lime, 3% polypropylene) which exceed the limitation (3-6)% due to
the higher concentration of plastomer (polypropylene) but the combination (1% hydrated lime,
1% polypropylene ) still agree the Iraqi specification but with higher values .The results of
Marshall test are shown in table (8) , figure (1) and figure (2).
International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
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Table (8): Marshall test results
Air Void
%
Stiffness
(kN/mm)
Flow
(mm)
Stability
KN))
Mix
Symbol
N.M.A.S
(mm)
Type of
Mixture
5.3 2.571 2.8 7.2 A1 25 (Control)
4.3 2.618 3.4 8.9 A2 19
5.0 2.613 3.1 8.1 A3 25 1% HL
&1%pp 4.4 2.833 3.6 10.2 A4 19
4.7 3.300 3.3 9.9 A5 25 1% HL
&2%pp 4.2 3.314 3.5 11.6 A6 19
6.1 2.194 3.6 7.9 A7 25 1% HL
&3%pp 4.9 2.333 3.9 9.1 A8 19
3.2 Indirect Tensile Strength
The evaluation of tensile strength for asphaltic concrete mixture is important due to fact that
the pavement will be exposed to various traffic loading and climatic condition. This is partially due
to the fact in service pavement during service .These conditions cause tensile stresses to be
developed within the pavement and as a result two types of cracks may be exhibited: one resulting
from traffic loading, called fatigue cracking, while the other resulting from climatic conditions,
called thermal or shrinkage cracking. As mentioned previously, one testing temperature has been
conducted to evaluate the resistance of mixtures at (20 0C). In tensile stress state, the mixture
strength depends on the cohesion element (asphalt) in resisting stresses.
The best combination was (1% hydrated lime, 2% polypropylene ) for indirect tensile
strength while other combination (1% hydrated lime, 1% polypropylene) & (1% hydrated lime, 3%
polypropylene) still agree the Iraqi specification but with lower values. The additive of plastomer
like polypropylene modify asphalt by forming a tough and rigid network within the binder to resist
deformation. While the additive hydrated lime helps to stiffer the mixture, after increasing the PG
rating of the binder by a full grade with the additive of only 1% HL. By stiffing the mix, the lime
increases it's resistance to rutting and fatigue cracking. The results of indirect tensile strength test are
shown in table (9) and figure (3).
Table (9): Indirect tensile strength test results
Type of Mixture N.M.A.S (mm) Mix Symbol Tensile Strength (MPa)
(Control) 25 A1 1.436
19 A2 1.329
1% HL &1%pp 25 A3 1.611
19 A4 1.796
1% HL &2%pp 25 A5 1.772
19 A6 2.497
1% HL &3%pp 25 A7 1.629
19 A8 1.511
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3.3 Index of Retained Strength Test Moisture-related problems are due to or are accelerated by:
• Adhesive failure – stripping of the asphalt film from the aggregate surface, or
• Cohesion failure – loss of mixture stiffness.
Adhesive failure in aggregates and asphalt occurs at an interface, while cohesive failure
occurs directly within asphalt or aggregate surface. These mechanisms can be associated with the
aggregate, the binder, or the interaction between the two ingredients. When weakening in the bond
between the aggregate and asphalt cement occurs, loss of strength of the HMA can be sudden in
some cases where the asphalt and aggregate are influenced by more than one factor or mechanism.
Iraqi specification (General Specification for Roads and Bridges Section R9 ) table R9/5
decides the IRS must be 70% minimum for mixture with all NMAS (base, binder). This test is
considered as indication of moisture damage sensitivity.
The results of all control mixtures don’t agree the requirements of Iraqi specification. The
best combination was (1% hydrated lime, 2% polypropylene ) for index of retained strength ratio
while other combination (1% hydrated lime, 1% polypropylene ) & (1% hydrated lime, 3%
polypropylene) still agree the Iraqi specification but with lower values. The additive of PP increases
the adhesion between aggregate and asphalt, which leads to decrease in stripping of HMA and
decrease in the horizontal deformation, and increase the tensile stiffness modulus values.
The addition of hydrated lime helps to mitigate moisture sensitivity of HMA in mechanical
ways as well as chemical .HL helps to stiffer the mixture, after increasing the PG rating of the binder
by a full grade with the additive of only 1% HL. By stiffing the mix, the lime increases it's
resistance
to rutting and fatigue cracking. In other words, when HL reacts chemically with AC, it may coat the
aggregate surface changing its bonding sites from acidic to basic. That transformation promotes
strong bonds between AC and aggregate . Prevent water from breaking them a part . HL also, reacts
with the acid component of the AC forming water in soluble calcium salts which protects the
adhesion bond. The results of index of retained strength ratio test are shown in table (10) and
figure (4).
Table (10): Index of retained strength test results
Type of
Mixture
N.M.A.S
(mm)
Mix
Symbol
Index of retained
strength %
(Control) 25 A1 59.5
19 A2 62.4
1% HL
&1%pp
25 A3 77.6
19 A4 93.8
1% HL
&2%pp
25 A5 78.5
19 A6 97.0
1% HL
&3%pp
25 A7 67.7
19 A8 72.3
International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
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• CONCLUSIONS
From the results of the experimental work obtained in this work, the following conclusions
are withdrawn:-
• Using hydrated lime together with polypropylene modified mixes exhibit high accordance and
exacerbates the improvement of properties for both mixes (25mm and 19mm) .
• For stability test as an indication of rutting problem, the best combination was (1% hydrated
lime, 2% polypropylene) which increased stability value of 1.3 times.
• The use of combination additives (1% hydrated lime, 2% polypropylene) achieved the
satisfactory values of Marshall stiffness with an increment of 1.25 times for modified HMA.
• The addition of hydrated lime for HMA mixture with additive combination decreased
significantly the % air voids of 1.2 times.
• For index of retained strength test as an indication of moisture damage problem, the use of
hydrated lime as an additive to HMA with polymer combination increased significantly the
index of retained strength ratio value of 1.3 times.
• For indirect tensile strength test an indication of fatigue cracks ,the best combination (1%
hydrated lime, 2% polypropylene) increased the indirect tensile strength value of 1.5 times.
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