Impact of Moisture Damage on Rutting Resistance, Shear and Tensile Properties of Asphalt Pavement

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International Journal of Scientific Research in Knowledge, 2(10), pp. 453-462, 2014

Available online at http://www.ijsrpub.com/ijsrk

ISSN: 2322-4541; 2014; Author(s) retain the copyright of this article

http://dx.doi.org/10.12983/ijsrk-2014-p0453-0462

453

Full Length Research Paper

Impact of Moisture Damage on Rutting Resistance, Shear and Tensile Properties of

Asphalt Pavement

Saad Issa Sarsam*, Ali Hussein Alwan

Department of Civil Engineering, College of Engineering, University of Baghdad, Iraq*Corresponding Author: Email:[email protected]

Received 19 July 2014; Accepted 08 September 2014

Abstract.In Iraq, under the effect of heavy traffic loading, high temperature and water damages, specific requirements are

needed to control the quality of highway pavement materials in order to increase durability. The primary objectives of thisstudy are evaluating the durability of superpave asphalt concrete mixtures which has been assessed through moisture damageresistance. The properties of superpave mix have been verified using indirect tensile strength test, double punch shear strength,compressive strength test, and rutting resistance under repeated loading. The impacts of moisture damage on such superpaveasphalt concrete properties were evaluated. To meet the objective of this research, available local materials were usedincluding asphalt cement (40-50), aggregate with nominal maximum size of 12.5 mm, and mineral filler. Three asphaltpercentages were implemented, optimum asphalt content and an asphalt content of 0.5 percent above and 0.5 percent belowoptimum as per superpave procedure. The Superpave Gyratory Compaction was used to prepare the asphalt concrete

specimens. The moisture damage impacts on conditioned specimens exhibits low resistance to indirect tensile strength,punching shear, and compressive strength by (-19%, -33%, -6%) at optimum asphalt content as compared with un-condition

mix.The moisture-conditioned mix has lower resistance to permanent deformation (at 1000 cycles) by 93% as compared withthe unconditioned mixture. Superpave asphalt concrete was shown to be durable against moisture damage by 81% at optimumasphalt content when compared to the requirement of (SCRB, 2007).

Keywords:Asphalt concrete; Indirect tensile; Moisture damage; punching shear; Retained strength; Rutting.

1. INTRODUCTION

Moisture damage is the loss of strength and durability

in asphalt mixtures due to the effect of water or

moisture vapor. It tends to accelerate the presence of

the distress types. The types of distress that can be

related to moisture or the other factors are bleeding,

cracking, rutting, and raveling, (Abed, 2006). It is

generally agreed that moisture can degrade the

integrity of bituminous mixtures in two ways; the first

mechanism is by causing a reduction in the cohesive

strength and stiffness of the mixture, characterized by

a softening of the mixture. The second mechanism is

by causing failure of the adhesion (or bond) between

asphalt and aggregate, referred to as stripping, (Terrel

and Shute, 1989). Pore pressure of water in the

mixture voids due to wheel-loading repetitions, and

temperature cycling above freezing, could be reported

as major causes of moisture damage.Asphalt removal by water, in the mixture at

moderate to higher temperatures, and Water-vapor

interaction with the asphalt filler mastic and larger

aggregate interfaces are also considered as possible

causes of water damage. The other major consequence

of moisture damage is that of a reduction of stiffness

and strength in the asphalt concrete layer, which

decreases the load spreading capabilities of the

pavement. Under the action of traffic loading, a

pavement with reduced stiffness due to water damage

is prone to rutting because of increased stresses and

strains in the underlying layers. Loss of strength in the

asphalt-aggregate matrix may also encourage

stripping, (Kennedy, 1985).

(Terrel and Al- Swailmi, 1994) showed that traffic

loading increases stripping. They conclude that

repeated loading (i.e., simulation of traffic loading) is

a very important variable to be included in water

conditioning protocols. AASHTO accepted the

Modified Lottman Test (AASHTO T-283) in 1985.

The aim of this work is to verify the resistance of the

superpave mix to moisture damage using indirect

tensile strength test, double punch shear strength,compressive strength test, and rutting resistance under

repeated loading.
mailto:[email protected]:[email protected]


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2. MATERIALS CHARACTERISTICS

2.1. Asphalt cement

Asphalt cement of grade (40-50) was brought from

Dura refinery. The asphalt properties are shown in

Table 1.

2.2. Aggregate

The aggregate used in this work is crushed quartz

from Al- Nibaie quarry. This aggregate is widely used

in local asphalt paving. Routine tests are performed on

the aggregates to evaluate their physical properties.

Test results are tabulated in Table 2.

2.3. Filler

Mineral filler used in this study is Portland cement

obtained from Badoush Factory; the physical

properties are as in Table 3.

Table 1: Properties of Dura asphalt cementProperty Unit Value SCRB Specifications

Penetration, 25 C, 100 gm, 5 sec (ASTM D-5- 06) 0.1 mm 41 40-50

Softening point, ring and ball (ASTM D-36- 95) C 49.4 --------

Ductility, 25 C, 5 cm/min (ASTM D-113) Cm 144 > 100Specific Gravity at 25C (ASTM D-70-97) 1.04After thin film oven test (ASTM D-1754)Retained Penetration, 25 C, 100 gm, 5 sec % 66 >55%

Ductility, 25 C, 5 cm/min Cm 87 >25%

Table 2: Properties of aggregatesProperties of Coarse aggregate ASTM Designation No. Value Superpave Specification

Bulk Specific Gravity C-127 -01 2.584 ----------------Percent Water Absorption C-127 -01 57% -------------------

Percent Wear (Loss Angeles Abrasion) C-131-03 13.08 45 % MaxPercent Soundness Loss by sodium sulfate solution C-88-05 2.678 20 % Max.

Percent flat and elongated Particles D-4791-05 1.6% 10 % Max.Percent Fractured faces ---------- 97% 95 % Min.

Properties of fine aggregateBulk Specific Gravity C-128-01 2.604 --------------Percent Water Absorption C-128-01 1.42 % ---------------Percent Sand equivalent D-2419-02 51 % 45 % Min.

Table 3: Properties of mineral fillerProperty % passing No.200 Bulk specific gravity Specific surface area Filler type

Value 96 3.15 312.5 m /kg Portland cement

2.4. Selection of Design Aggregate Gradation

The Superpave aggregate gradation controls are

maintained using the FHWA 0.45 power chart. This

chart uses a unique technique where the ordinate

shows the percent passing and the abscissa is an

arithmetic scale of sieve size in millimeters, raised to

the 0.45 power. The aggregate blend selected has

nominal maximum size of 12.5 mm usually adopted

for wearing course as per (SCRB, 2007). Fig.1 shows

the selected aggregate gradation.

Fig. 1: Selected gradation of wearing course


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3. PREPARATION OF SPECIMENS FOR

RESISTANCE TO MOISTURE DAMAGE TEST

The aggregate are dried, separated into the desired

size and recombined with the mineral filler in order to

meet the required gradation. The aggregates are then

heated to a temperature of 160 C before mixing with

asphalt cement which has already been heated to a

temperature that produce a kinematic viscosity. Then,

the desired amount of asphalt cement is weighed,

added to the heated aggregates, and mixed until all

aggregate particles are coated with asphalt. Four

asphalt binder contents, at 1% of the estimated asphalt

content, and at 0.5 % increments have been

implemented and prepared. Test specimens of 115

mm in diameter and 1505 mm in height were

prepared according to method AASHTO TP4. Theoptimum asphalt content was 4.8%.

Three sizes of cylindrical specimens were prepared

for evaluating the impact of moisture damage,

Specimen of 150 mm in diameter and 955 mm in

height were constructed for indirect tensile strength

and tensile strength ratio. Specimens of 101.6 mm in

diameter and 101.61.3 mm in height were prepared

for Double Punch Test, Compressive Strength test,

and Index of Retained Strength Test. The third size

was specimens of 101.6 mm in diameter and 2033

mm in height for Permanent Deformation tests.

Specimens were prepared at optimum asphalt contentand at asphalt contents of 0.5 percent above, and 0.5

percent below optimum as recommended by

superpave procedure (AASHTO PP2, 1999). The

asphalt-aggregate mixture was then subjected to short-

term oven aging (STA) for 4hrs at 135 C according

to (AASHTO PP2). This aging represents the aging

that occurs in the field between mixing and placement

and allows for absorption of the asphalt binder into

the aggregate pores. The mix was stirred every 30

minutes during the short-term aging process to

prevent the outside of the mixture from aging more

than the inner side because of increased air exposure.Mixing and compacted HMA sample according to

AASHTO TP4 to the level of compaction required for

the tests to be conducted. They were compacted using

gyratory compactor at air void content of 71 percent,

which was fixed by changing number of gyrations and

pressure of 600 kPa. Specimens were considered

conditioned after they were subjected to vacuum

saturation followed by a freeze cycle followed by a 24

hour thaw cycle. Tests were accomplished by

performing AASHTO T-283. The total number of

specimens was (70 specimens).

3.1. Compressive Strength Test

This test is conducted to determine the suitability of

asphalt concrete mixtures for pavement under given

loading and environmental conditions. The test

followed the procedure of (ASTM D1074-02).Compressive strength specimens which were prepared

and stored in air bath at 25C for 4 hours, then, the test

was performed by applying a compressive load at a

constant rate of 5.08 mm/min to measure the

maximum load at failure. Fig.2 shows part of the

prepared specimens.

3.2. Double Punch Shear Test

Jimenez (1974) developed this test procedure at the

University of Arizona, and it was used to measure the

stripping of the binder from the aggregates, this testwas reported by many studies (Solaimanian, 2004;

Turos, 2010; Kiggundu, 1988; Sarsam, 2006).

Specimens used for this test were conditioned by

placing them in water bath at 60C for 30 min. The

test was performed by centrally loading the cylindrical

specimen, using two cylindrical steel punches placed

on the top and bottom surface of the sample. The

specimen was centered between the two punches (25.4

mm in diameter), perfectly aligned one over the other,

and then loaded at a rate of 25.4 mm/minute until

failure. The reading of dial gage at the maximum load

resistance was recorded. Fig.3 shows double punchshear test in progress.

Fig. 2:The compressive strength and IRS test specimens


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3.3. Index of Retained Strength Test

This method covers measurement of the loss of

cohesion resulting from the action of water on

compacted asphalt concrete mixtures. The test

followed the procedure of (ASTM D1075-07). A set

of four specimens were prepared for this purpose.

Two specimens were stored at air bath for 4 hours at

25C, and then tested for compressive strength and the

average value was recorded. The other two specimens

were stored in water bath at 60C for 24 hours, then

they were stored in another water bath at 25C for 2

hours, and the compressive strength test was

performed on these specimens, and also the average

value was recorded.

3.4. Indirect Tensile Strength and tensile strength

Ratio Test (TSR)

The test was performed to evaluate the moisture

damage resistance of mixtures, and the procedure

followed (AASHTO T 283). A set of four specimens

were prepared, two specimens were tested for indirect

tensile strength (ITS) by storing them in a water bath

at 25C for 30 minutes, and an average value of ITS

for these specimens was computed (ITS for

unconditioned specimens). The other two specimens

were subjected to vacuum saturation between 70 and

80 percent with water and is placed in the freezer (-

18C) for 16 to 18 hours. The frozen specimens then

are moved to a water bath at (60C) for 24 hours

(thaw cycle), then they were placed in a water bath at

25C for 1 hour, and they were tested for indirect

tensile strength, the average value was computed (ITS

for moisture-conditioned specimens). The specimens

were tested for the resilient modulus, indirect tensile

strength, indirect tensile strength ratio, double punch,

compressive strength, and permanent deformation.

Two specimens for each mixture type were tested, and

the average value was recorded. The ratio of the

average tensile strengths of the conditioned andunconditioned specimens is known as the tensile

strength ratio (TSR). The minimum acceptable TSR as

per AASHTO is 70%, (Roberts et al., 1996). The

results of these specimens are compared, to clarify the

effect of unconditioned and conditioned mix on

mixture performance. Fig.4 shows the vacuum

saturation, while fig.5 shows the failure mode of ITS

test specimen. On the other hand, fig.6 presents the

freeze- thaw cycle process.

Fig. 3: Double punch sheartest Fig. 4: Specimens under vacuum process Fig. 5: Indirect tensile test

Fig. 6:The freezing and thawing conditioning process


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3.5. Permanent Deformation Test

The axial repeated load tests were conducted using the

pneumatic repeated load system (PRLS). The tests

were performed on cylindrical specimens, 101.6 mm

(4 inch) in diameter and 203.2 mm (8 inch) in height.

In these tests, repetitive compressive loading was

applied to the specimen and the axial permanent

deformation was measured under loading repetitions.

Compressive loading was applied in the form of

rectangular wave at a constant loading frequency of

60 cycles per minute and two different loading

sequences; which included 0.1 sec. load duration and

0.9 sec. rest period to simulate the truck loading

condition in the field as per shell procedure. Two

temperatures 40 C, and 60 C are used in the tests,

and the applied stress level was 20 psi.to simulate thetesting condition explained by Shell procedure thats

addressed in (Moghaddam et al, 2011; Yoder and

Witczak, 1975). The testing temperatures of (60, 40)

C was used in the test, and the applied stress level

was 20 psi. fig.7 shows the tested specimen in the

repeated loading chamber, while fig.8 demonstrates

the schematic diagram of accumulation of permanent

strain under repeated loading.

Fig. 7: Permanent deformation test Fig. 8: Accumulation of permanent strain under repeated loading

4. DISCUSSION OF TEST RESULTS

4.1. Impact of Moisture Damage on Indirect

Tensile Strength and Tensile Strength Ratio

The indirect tensile strength (ITS) property of an

HMA mix gives an indication on the overall strength

of the mix. Fig.9 depicts the effect of moisture on

indirect tensile strength. Results indicated that tensile

strength at 60 C for conditioned specimens has

reduced by 19% as compared to un-conditioned

specimens at optimum asphalt content. Tensile

Strength Ratio (TSR) as shown in fig.10 has beenused for predicting moisture susceptibility of

mixtures. The recommended limit of (80 %) for

tensile strength ratio (TSR) is used to distinguish

between moisture susceptible mixture and moisture

resistance mixtures (AASHTO T-283). The tensile

strength ratio was 81%, at optimum asphalt content

mix. Also it could be noted that increasing asphalt

content percentage from 4.3 % to 4.8 % had increases

resistance to indirect tensile forces by 19 %, while

when increasing the binder from 4.8 % to 5.3 %, the

indirect tensile strength decreases by 23 % (for un-

conditioned mix). It gives an indication that theoptimum asphalt content percentage and above has

good resistance to the impact of moisture damage.

Such results agrees well with (Sarsam and Al-azawi,

2013; Parker and Gharaybeh, 1987) findings.

4.2. Impact of Moisture Damage on Punching

Shear

Double punch test indicates the stripping behavior

between binder and aggregate. Results of double

punch test show that the punching shear strength for

conditioned mix is less than unconditioned mixturesby 33%, at optimum asphalt content. In addition, it is

noted from Fig.11 that the punching strength increases

as asphalt content increase up to an optimum, then it

decreases with further increment in asphalt binder for

both conditioned and unconditioned mixes. Therefore,

punching strength increases by 109 % as asphalt

content increases from 4.3 % to 4.8 %, but decreases

by 38 % as asphalt content increases from 4.8 % to

5.3 % for unconditioned mixes. Fig.12 shows

Punching shear Strength Ratio.


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Fig. 9:Indirect tensile strength of asphalt concrete Fig. 10:Tensile strength ratio %TSR of asphalt concrete

Fig. 11:Punching shear strength of asphalt concrete Fig. 12:Punching shear ratio of asphalt concrete

4.3. Impact of Moisture Damage on Compressive

Strength and Index of Retained Strength (IRS)

The index of retained strength (IRS) has been used to

evaluate the resistance of mixture to water damage.

According to (SCRB, 2007), the minimum acceptable

value of Index of Retained Strength is (70%),

therefore mixture with lower IRS is considered

susceptible to water damage. The detailed results for

compressive strength test are presented in Fig.13,

while Fig.14 present the Index of Retained Strength.The compressive strength values of the conditioned

mixtures were lower than the unconditioned mixtures

by 6 % (at optimum asphalt content). When asphalt

content percentage increases from 4.3 % to 4.8 %, the

resistance to compressive forces increases by 1 % for

unconditioned mix, while when asphalt content

increases from 4.8 % to 5.3 % the compressive

strength increase 9 % for unconditioned mixes. Such

finding are in agreement with (Sarsam, 2005) work.

Results of IRS shows a good performance of optimum

asphalt content percentage as shown in Fig.14, it

shows that mixes with variable asphalt content areconsidered unsusceptible to moisture damage since it

has IRS more than (70%). These values meet the

design criteria established by the Iraqi Specification

(SCRB, 2007).

4.4. Impact of Moisture Damage on Resilient

Modules (Mr)

The resilient modulus (Mr) properties are used to

evaluate the moisture damage of the HMA mixtures,

the Mr test is a nondestructive test that can be

conducted on the same samples before and after

moisture conditioning, the Mr is an engineeringproperty that can be used to estimate the response of

HMA pavements under traffic loads, (Tara, 2003).

Table 4 summarizes the Mr properties of the

unconditioned and moisture conditioned HMA

mixtures. The data show that the resilient modulus of

moisture-conditioned specimens is significantly lower

than the values obtained for unconditioned mix by

21% at optimum asphalt content. When the asphalt

content percentage change from 4.3 to 4.8 percentages

the Mr value decreases by 18%, and decreases by 27%

when asphalt content changes from 4.8 to 5.3 %. The

change in testing temperature from 40 to 60 C has anegative influence on Mr by 20% at optimum asphalt

content.


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Fig. 13:Compressive strength of asphalt concrete Fig. 14:Index of retained strength %IRS of asphalt concrete

4.5. Impact of Moisture Damage on Resistance to

Permanent Deformation

Table 4 shows the impact of moisture on permanent

deformation. The analysis of permanent deformation

in this study is based on intercept, and slope

parameters and permanent deformation at 1,000 load

cycles. The pneumatic repeated load system was

implemented. The permanent deformation (vertical

plastic strain) is measured using the dynamic test at

temperature of 40 C and 60 C, with a stress level of

0.138 MPa. The intercept represents the permanentstrain at N=1, where N is the number of the load

cycles. The higher value of intercept, the larger strain

and hence the larger the potential for permanent

deformation as mentioned in the study carried out by

(Sarsam and AL-Zubaidi, 2014). While slope

represents the rate of change in the permanent strain

as a function of the change in loading cycles (N) in

the log-log scale, high slope values for a mix indicate

an increase in the material deformation rate hence less

resistance against rutting. A mix with a low slope

value is preferable as it prevents the occurrence of the

rutting distress mechanism at a slower rate. The

analysis of the table shows that the moisture

conditioned mix has lower resistance to permanent

deformation (at 1000 cycles) by 93% as compared

with the unconditioned mixture; it has shorter life and

fails before the unconditioned mix. Such finding is in

agreement with (Sarsam and Lafta, 2014; Sarsam,

1999). The higher permanent deformation is

associated with the increases in asphalt content. It can

be seen that the intercept and slope increases in

conditioned mix, that gives indication that the un

conditioned mixtures have low permanent microstrainas compared with conditioned mix. Table 4 shows the

effect of temperature on permanent microstrain, when

testing temperature changes from 40 to 60 C, the

permanent microstrain increases. Fig.15 show the

impact of moisture damage on the permanent

deformation at both testing temperatures and various

asphalt percentages. The resilient modulus decreases

after moisture damage for all asphalt percentages,

while it decreases as asphalt percentages increases as

demonstrated in table 4.

Table 4:Deformation Properties of asphalt concreteAsphaltcement

%

Mixture type 40C 60C

Intercept Slope Permanent

microstrain@ 1000

cycle

Resilient

modulusMPa

Intercept Slope Permanent

microstrain@ 1000

cycle

Resilient

modulusMPa

4.3 Unconditioned 83 0.472 2157 8177 226 0.460 5424 6308Conditioned 182 0.454 4188 7359 366 0.454 8435 5810

4.8 Unconditioned 149 0.441 3158 6690 402 0.508 13505 5384Conditioned 259 0.457 6083 5256 432 0.543 18498 4415

5.3 Unconditioned 317 0.583 17799 4906 292 0.710 29513 4014

Conditioned 436 0.607 28962 5017 441 0.477 31887 3560


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Fig. 15: Permanent deformation of asphalt concrete at various asphalt content and testing temperatures

5. CONCLUSIONS

Based on limited testing program, the following

conclusions could be drown:1. Superpave asphalt concrete was shown to be

durable against moisture damage by 81% at optimum

asphalt content when compared to the requirement of

SCRB (2007). The impact of moisture conditioning of

superpave asphalt concrete is lowering the indirect

tensile strength, punching shear, and compressive

strength, by (19%, 33%, and 6%) respectively as

compared with un condition mix.

2. The increase in asphalt content from the

optimum to 0.5% above optimum leads to decrease

the indirect tensile strength, double punching shear

and compressive strength after impact of moisturedamage by 23%, 38% and 9% respectively. that gives

indication that the optimum asphalt content gives

higher resistance to moisture damage at the same air

void content (71 %) when compared with other

asphalt percentages.

3. Resilient modulus Mr shows higher values for

moisture conditioned mixes as compared withunconditioned mix by (5%, 2 %) respectively, but Mr

h s lower value by (21%, 18%) respectively after

moisture damage at optimum asphalt content.

4. The permanent deformation decreases by 12

percent at STA, but permanent deformation increases

by 93 percent after subjecting the specimen to

moisture damage, at optimum asphalt content. An

asphalt content change from 4.8 to 5.3 percent causes

a 43 percent increase in permanent deformation. A

temperature change from 40 to 60 C causes a

reduction in permanent deformation by 113 percent.


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Prof. Saad Issa Sarsamwas born in Baghdad (1955), got his BSc. In Civil Engineering (1977), Postgraduate diploma in Transportation Engineering (1978); MSc in Transportation Engineering (1980).

He worked as senior material Engineer for NCCL (1982-1992); He joined the academic staff atUniversity of Mosul (1992-2005) and got the Assistant Professor degree at (2002); He joined the

academic staff at University of Baghdad (2005 until now) and got the Professor degree at (2007).Areas of specialization and interest: (Roller compacted concrete; modified asphalt concrete; Asphalt

stabilized embankment models; Road user characteristics).

Ali Hussein Alwan was born in Baghdad, (1987), got his BSc. in Civil Engineering (2011), MSc. inCivil Engineering (Transportation),( 2013). Worked for Al-Hamed Company as supervising Engineer

on Building of International football stadium Municipality of Al-Muthana (2011-2012). He worked forCity Dimension Contracting Company as Soil investigation engineer on the construction of oil storage

tanks /Municipality of Al-Basra. (2012-2013). Worked for Osman Qader Company as SurveyorEngineer on construction of a sewage disposal station (Al-Hussenia)/Municipality of Baghdad (20132014). He is working for Setraco Company as site engineer and as QC and QA on construction ofroads and bridges, Baghdad- Karbala Project.(2014 until now).

Documents

Impact of Moisture Damage on Rutting Resistance, Shear and Tensile Properties of Asphalt Pavement