Performance evaluation of asphalt mixture modified by hydrated lime and polypropylene

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

© IAEME: www.iaeme.com/ijciet.asp

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177

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).



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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.



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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).



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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).



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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.



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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).



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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).



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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



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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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