Impact of Asphalt Additives on Rutting Resistance of Asphalt Concrete

8/12/2019 Impact of Asphalt Additives on Rutting Resistance of Asphalt Concrete

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International Journal of Scientific Research in Knowledge, 2(3), pp. 151-159, 2014

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

ISSN: 2322-4541; 2014 IJSRPUB

http://dx.doi.org/10.12983/ijsrk-2014-p0151-0159

151

Full Length Research Paper

Impact of Asphalt Additives on Rutting Resistance of Asphalt ConcreteSaad Issa Sarsam*, Ibtihal Mouiad Laftaa

Department of Civil Engineering, College of Engineering, University of Baghdad, Iraq,

*Corresponding Author: Email:[email protected]

Received 9 January 2014; Accepted 21 February 2014

Abstract.Rutting is considered as one of the major pavement distresses of flexible pavement in Iraq. The hot weather durationfor five months with 40-50 C has negative impact on the rutting resistance of asphalt concrete pavement. It was felt that

modification of asphalt cement may be a possible solution to overcome such issue. In this paper, two penetration grade asphalt

cement (40-50 and 60-70) have been modified in the laboratory by digestion with five types of locally available additives (fly

ash; crumb rubber; fumed silica, sulfur; and Phospho-gypsum). Asphalt concrete mixture usually used for wearing courseconstruction in Iraq as per SCRB specifications of 19 mm nominal size was considered in this investigation. Specimens were

prepared using both of conventional asphalt cement and modified asphalt cement. The prepared modified asphalt concrete

mixtures were evaluated by using Marshall Tests, resilient modulus determination (MR) and resistance to permanent

deformation under repeated loads test, and then compared with the conventional mixture. The asphalt concrete mixtures

modified by 10% fly ash by weight of asphalt cement (60-70) exhibit high resistance to permanent deformation as compared

with the control mixture, while the mixture modified by 3% sulfur by weight of asphalt cement (60-70) generally showed

lower resistance to permanent deformation as compared to the other tested mixtures. On the other hand, 1% of Phospho-

gypsum by weight of asphalt cement (40-50) exhibit an improvement in rutting resistance. Sulfur and fly ash showed negative

impact on rutting resistance for the range of load repetition studied.

Keywords: Asphalt additives; Dynamic indirect tensile tests; Modified asphalt concrete; Resilient modulus.

1. INTRODUCTION

Over the past few years, road network in Iraq havebeen subjected to more severe traffic conditions

characterized by an increase in the number ofvehicles, the load limits and by tire inflation pressures(Sarsam, 2008). Asphaltic material with aggregate isusually used as a pavement mixture which is designed

considering flexibility, durability and stability.Despite the use of asphalt mixes poor in binder qualityand the enforcement of stricter specifications formaterialsespecially asphalt, the limits of mechanicalstability of road surfacing have often been exceededand this has resulted in damage such as cracking anddeformation. Increasing the resistance to permanentdeformation and improving the resistance to fatigueat low temperatures could mark a good start, on the

other hand, improving binder-aggregate adhesion(higher viscosity of the binder), Slowing down theageing process (thicker film of binder around theaggregate) are considered to be vital for long termservice of the pavement (Vonck and Van, 1989).

The effect of fumed silica and Phospho - gypsum asadditives have been studied by Sarsam (2012), and its

positive impact on asphalt rheological and physicalproperties were pointed out. Dong et al. (2011)investigated the properties of hot-mix asphalt (HMA)prepared with de-vulcanized crumb rubbermodified

asphalt. A series of laboratory tests including thesubmerged Marshall Stability, wheel tracking test,dynamic modulus test, small beam bending test, andfour-point flexural fatigue test, were carried out to

characterize the properties of HMA. They concludedthat the pre de- vulcanized crumb rubber can be usedas one kind of good modifier for asphalt rubber toimprove hot storage stability.

Cooper et al. (2011) compared the laboratorymechanistic properties of sulfur-modified warm-mixasphalt (WMA) with conventional asphalt mixtures. Asuite of tests was performed to evaluate the ruttingperformance, moisture resistance, fatigue endurance,

fracture resistance, and thermal cracking resistance ofthe three mixtures. Results of the experimentalprogram showed that the rutting performance ofsulfur-modified WMA was comparable or superior toconventional mixes prepared with polymer-modified

and unmodified asphalt binders. Coplantz et al. (1993)evaluated sulfur-asphalt rutting resistance. The
mailto:[email protected]:[email protected]:[email protected]:[email protected]


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Impact of Asphalt Additives on Rutting Resistance of Asphalt Concrete

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existing asphalt pavement was cracked and rutted. An85/100 pen asphalt was used to make the sulfurasphalt binder. The sulfur-asphalt mixtures had higherresilient moduli than control by approximately 30% at22 C and 50% at 4C. . The rut depths in all sectionsincreased slightly over time, and the depths for allsections were approximately equal after one and five

years. The rut depths on the original pavement werehigher in the sulfur-asphalt test section locations.Aliet al. (1996) studied the effect of fly ash on themechanical properties of asphalt mixtures to evaluatethe effect of using fly ash in mitigating pavement

distress and improving performance of asphaltconcrete pavement. This study evaluated four groups

of specimens with various fly ash contents and 5%asphalt content. They concluded that fly ash, when

used as a mineral, improved strength and strippingresistance. Mechanical properties testing resultsindicated that the use of 2% fly ash improved the

resilient modulus of the mix at high and lowtemperatures. Kumar, et al. (2010) stated that theclimatic conditions play an important role in selecting

the type of materials to be used in road construction.In order to increase the life of bituminous pavement,quality of bitumen needs to be enhanced. To achievethe improvement of binder, it is necessary to add thepolymers to bitumen. It indicates that the SBS-modified binder is more resistant to cracking andrutting at low as well as high temperatures hand, by

addition of 3% EVA with 60/70 bitumen, the ruttingresistance is substantially increased at 58C.

The aim of this study is to verify the impact ofusing five different types of additives in modificationof two types of asphalt cement on resilient modulus,

resistance o deformation under load repetitions, andMarshal properties of modified asphalt concrete.

2. MATERIALS AND METHODS

The materials used in this study are asphalt cement,aggregate, mineral filler and additives. The properties

of these materials were evaluated using routine typesof test.

Table 1:Properties of asphalt cementProperty Asphalt cement (40-50) Asphalt cement (60-70)

PenetrationSoftening point

Ductility

4450

>100

6648

>100

Table 2: Physical properties of aggregateProperty Coarse aggregate Fine aggregate

Bulk specific gravity 2.610 2.640

% water absorption 0.448 0.720

Abrasion% (Los Angeles) 22.2 % ----------

Table 3:physical properties of mineral fillerProperty Test results

Specific gravity 2.794

% Passing sieve No.200 (0.075mm) 94

Table 4:physical properties of asphalt additivesAdditive type Fly ash Fumed silica Sulfur Crumb rubber Phospho-gypsum

Specific gravity 2.010 0.16 2.070 1.130 2.350

Specific surface area (m2/kg) 700 100000 ------ ----------- 500

2.1. Asphalt cement

For the purpose of this work, two types of penetrationgrade asphalt cement were considered, (40-50) and

(60-70). Both types are obtained from the Durarefinery, south-west of Baghdad. The asphalt cementproperties are shown in Table 1.

2.2. Aggregate

The coarse aggregate used in this work was crushedaggregate obtained from AL-Nibaai quarry. Thecoarse and fine aggregates used in this work were

sieved and recombined in the proper proportions tomeet the wearing course gradation as required bySCRB specification (SCRB, R/9. 2007). The wearingcourse was selected because this layer is always in

direct contact with traffic loadings and variations inenvironmental conditions. Routine tests wereperformed on the aggregate to evaluate their physicalProperties. The results are summarized in Table 2.The selected gradation with specification limits are

presented in Figure 1.


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2.3. Mineral Filler

The mineral filler used in this work is limestone dustobtained from the lime factory in Karbalagovernorate. The physical properties of the used fillerare presented in Table 3 below:

2.4. Asphalt additives

Five types of additives were implemented in thiswork; their physical properties are shown in Table 4.

Table 5:Marshall Test Result for asphalt cement (40-50) mix.Additive (%) Asphalt Stability (kN) Flow (mm) Bulk density (gm./cm ) Voids (%) Vfa (%) VMA (%)

Control 4.5 8.2 2.3 2.3225 5.358 68.1 16.8

5 11.7 2.5 2.33 4.39 72.7 16.1

5.5 9.5 2.8 2.335 3.5123 77.3 15.4

5%

Rubber

4.5 8.9 2.2 2.321 4.09 75.7 16.8

5 10.0 2.7 2.365 2.954 79.4 14.3

5.5 9.0 3.0 2.396 2.363 82.1 13.2

5% Flyash

4.5 9.2 2.2 2.321 4.09 73.2 16.8

5 10.3 3.0 2.341 3.939 74.1 15.2

5.5 9.4 3.7 2.358 3.911 75.7 14.6

1%Fumedsilica

4.5 9.5 2.7 2.293 6.56 61.3 16.95 10.5 3.0 2.322 4.718 71.2 16.4

5.5 10.0 3.2 2.331 3.677 77.7 16.5

1%Phospho

- gypsum

4.5 6.9 2.2 2.296 6.438 61.8 16.8

5 8.3 2.7 2.318 4.883 70.4 16.5

5.5 7.9 3.0 2.332 3.636 77.9 16.4

5%

Sulfur

4.5 8.7 2.2 2.308 4.628 73.2 17.3

5 10.1 3.0 2.345 3.775 75.7 15.5

5.5 9.1 3.1 2.335 3.5123 76.1 14.7

Fig. 1:Gradation Curve of Aggregate used for Wearing Course.

Fig. 2:Part of the prepared specimens Fig. 3:Mode of failure after load repetitions


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3. RESULTS ANDTESTING PROGRAM

The testing program was divided into two phases, inthe first phase; the modified asphalt cement wasprepared in the laboratory as follows:

Asphalt cement was heated to a temperature of160C for asphalt cement (40-50), 150C for asphalt

cement (60-70), and then additive in its powder formwas added gradually and mixed using manual stirringon the hot plate for 60 minutes as a constant blendingtime. Three percentage of each type of additive wasconsidered, and an optimum additive content was

selected based on physical properties determination ofthe blend. The details of the testing was published

elsewhere (Sarsam and Lafta, 2014). For asphaltcement (40-50), the selected additives were (5%

rubber; 5% fly ash; 1% fumed silica; 5% sulfur; 1%Phospho-gypsum), on the other hand, the selectedadditives percentages for asphalt cement (60-70) were

(7% rubber; 10% fly ash; 3% fumed silica; 3% sulfur;3% Phospho-gypsum).

The second phase consist of preparation of asphaltconcrete specimen using Marshal Test procedure, suchspecimens have been implemented for Marshal

properties and resilient modulus determination, andfor indirect tension repeated load test. Figure 2

illustrates part of the prepared specimens.

3.1. Marshall Test

Marshall Test has been implemented to find theoptimum asphalt content; it was conducted on acylindrical specimen (101.6 mm) diameter and (63.5mm) height. Asphalt was heated up to 160

0C prior to

mixing for asphalt cement (40-50) and1500C prior to

mixing for asphalt cement (60-70), and it was addedto the hot aggregate and mixed thoroughly at (160

0C)

in the bowl for two minutes, then was placed in themold and compacted with 75 blows on each face ofthe specimen, using hammer of 4.53 kg sliding weight

and a free fall of (457.2 mm). The optimum asphaltcontent was (5 %). Test specimens were fabricated for

a range asphalt contents (4.5, 5, and 5.5) % by totalweight of the mix as per the requirements of super-pave.

3.2. Indirect Tension Repeated Load Test (IDT)

The indirect tension repeated load test specified by(ASTM D4123) was conducted using the pneumaticrepeated load system (PRLS). The tests wereperformed on Marshall Specimens. In these tests,repetitive loading is applied to the diametric specimenand the resilient vertical strain is measured under the

load repetitions. Diametric loading is applied with aconstant loading frequency of 60 cycles per minute

and loading sequence for each cycle is 0.1 sec loadduration and 0.9 sec rest period. Two testing

temperatures (25, 40) C have been implemented, andthe applied stress level was 0.138 MPa. The specimenwas placed in the testing chamber for two hours at

40C or 25 C to allow for a uniform temperaturedistribution within the specimen. The experiment wascommenced by application of repeated stress andrecording the permanent deformation. The dial gaugewas set to zero reading after completion of the

specimen "setup" in the testing equipment. Thepressure actuator was adjusted to the specified stress

level. The timer (both loading port and rest port) wasalso set to the required load and rest durations. A

video camera was located at proper place to cover theview of dial gauge reading and set ready to startrecordings. Upon completion of test, the number ofload repetitions was recorded when the specimenfailed. The required deformation data analyses includethe determination of the permanent deformation at thefollowing load repetitions: (1, 10, 50, 100, 200, 300,400, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000,5000, 6000 ) or until the specimen failed. Thepermanent vertical strain was measured as a functionof the number of load applications at 40C and stressof 0.138 MPa. Figure 3 shows the failure mode after

load repetitions, while figure 4 shows the repeatedload testing system.


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Fig. 4:Repeated load testing system

Table 6: Marshall Test Result for asphalt cement (60-70)Additive (%) Asphalt Stability (kN) Flow (mm) Bulk density (gm./cm ) Voids (%) Vfa (%) VMA (%)

Control 4.5 7.625 2.25 2.309 6.593 59.8 16.4

5 10.408 2.875 2.3542 4.074 73.2 15.2

5.5 8.755 4.125 2.373 2.626 82.4 14.9

7% Rubber 4.5 6.475 2.75 2.312 6.472 60.3 16.3

5 7.959 3 2.336 5.215 65.9 15.3

5.5 7.437 3.75 2.372 1.969 86.3 14.4

10% Fly

ash

4.5 8.652 1.75 2.322 6.067 58.5 15.9

5 10 2 2.337 4.767 69.9 15.8

5.5 8.952 2.5 2.348 3.652 77.0 15.8

3% Fumedsilica

4.5 7.435 1.5 2.326 5.909 62.8 15.9

5 8.897 1.75 2.336 4.808 69.3 15.7

5.5 7.643 2.25 2.355 3.364 77.3 15.6

3%

Phospho-gypsum

4.5 7.765 1.75 2.314 6.391 60.6 16.2

5 8.081 2 2.328 4.96 69.3 16.1

5.5 7.543 2.75 2.336 4.144 74.6 16.3

3% Sulfur 4.5 6.345 2 2.342 5.258 65.4 15.2

5 7.346 2.5 2.356 3.993 73.7 15.1

5.5 7.215 3 2.357 3.282 78.9 15.5

Table7:Resilient Modulus value for asphalt concrete mixtureSpecimen Resilient Modulus(MPa)

Asphalt cement (40-50)

Resilient Modulus (MPa)

Asphalt cement (60-70)

Control at (25C) 267.2 298.8

Control at (40C) 248.6 268.45% rubber (40C) 284.2 -----

7% rubber (40C) ----- 277.5

5% fly ash (40C) 242.2 -----

10% fly ash (40C) ------ 249.0

1% fumed silica (40C) 238.0 ------

3% fumed silica (40C) -------- 248.8

1% Phospho-gypsum (40C) 258.7 -------

3% Phospho-gypsum (40C) ------ 248.6

5%sulfur (40C) 233.8 259.5

4. DISCUSSIONS ON TEST RESULTS

4.1. Marshall Test

A series of tests for Marshall stability, flow ,anddensity-voids analysis were carried out for selectingthe optimum asphalt content for mixtures by using

aggregate (12.5 mm nominal maximum sizegradation),7 percent lime stone dust (by weight of the

total aggregate), and three different asphalt contents(4.5,5 and 5.5%) of (40-50) ,(60-70) penetrationgrade. Three specimens are prepared and tested foreach mix variable. Tables 5 and 6 present MarshallProperties for asphalt cement (40-50), (60-70)


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respectively. The stability of mixtures containing 5%rubber by wt. of asphalt cement (40-50) was lowerthan that of control mixtures, and the stability ofmixtures containing 3% sulfur by wt. of asphaltcement (60-70) was lower than those of controlmixtures. While specimens containing 1% fumedsilica by wt. of asphalt cement (40-50) had almost

higher stability values than the other percent ofadditives. Change in stability values of the mixturecontaining additives, may be attributed to the changein bulk density and voids of the mix.

The flow values increased when additives were

introduced to asphalt cement 40-50. The values weresignificantly higher for 1% fumed silica than the

control specimens. The flow value decrease whenadditives were added to asphalt cement (60-70). These

changes in flow values could be attributed to thechange in viscosity of asphalt cement. Voids

decreases as the additives were introduced in the mixand the introduction of additives have also increasedthe voids filled with asphalt in general. The increaseof Vfa indicates an increase of effective asphalt filmthickness between aggregates, which will results indecreasing cracking.

Specimens containing 5% rubber by wt. of asphalt

cement (40-50) had the lowest air void contentsamong other mixes. It was also noted that thespecimens made with 7% rubber by wt. of asphaltcement (60-70) contents had lower air void contentsthan the other specimens.

The VMA property is significant as far as thepavements of hot regions are concerned because

asphalt may be prone to bleeding and amounting voidratio could prevent bleeding by providing more spaces

for the binder to move through. This was probably dueto greater surface areas to be coated.

a.) Mixes with 40-50 asphalt cement b.) Mixes with 60-70 asphalt cement

Fig. 5: Impact of testing temperature onrutting resistance of asphalt concrete

4.2. Resilient Modulus Test

The resilient modulus represents the ratio of anapplied stress to the recoverable strain that takes place

after the applied stress has been removed. Thefrequency of load application used in this work is 1Hz, with load duration of 0.1 sec and a resting periodof 0.9 sec to simulate the field conditions. Generally,higher modulus indicates greater resistance todeformation. Resilient modulus is determined at 40Ctemperature and a stress level of 0.138 MPa; testingprocedures are in accordance with (ASTM D4123).

Table 7 demonstrated that Resilient modulus of 5%rubber by wt. of asphalt cement (40-50) wassignificantly higher than the values obtained forcontrol mixture, while 10% fly ash by wt. of asphaltcement (60-70) shows almost higher values amongother additives. Generally, higher moduli indicate

greater resistance to deformation. A high modulusasphaltic surface layer will also protect the subgrade

from being overstressed and therefore it will reducethe probability of subgrade failure as cited by (Huang,

1993).

4.3. Resistance to Permanent Deformation

Figure 5 presents the impact of testing temperature onaccumulation of permanent strain for both types ofasphalt cement. The slope represents the rate ofchange in the permanent strain as a function of thechange in loading cycles (N) in the log-log scale. High

slope of the mix when tested at 40 C indicates anincrease in material deformation rate, hence, lessresistance against rutting. A mixture with low slope is

preferable as it prevents the occurrence of rutting. Onthe other hand, the intercept (a) represents the


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permanent strain at N=1 (N is the number of loadcycles), the higher the value of (a), the larger is the

strain and the potential of permanent deformation.

a.) Mixes with 40-50 asphalt cement b.) Mixes with 60-70 asphalt cement

Fig. 6:Impact of asphalt additives on deformation behavior under load repetitions

Figure 6 shows the permanent micro strain, givenas a function of load applications. The figure showsthe effect of additives to asphalt cement (40-50) and(60-70) .Recognizing the fact that the lowerpermanent strain is related to the lower sensitivity forrutting and corrugation, it means that the modifiedbitumen mixes have a beneficial influence on the mixproperties. The mixtures modified by 5% rubber bywt. of asphalt cement (40-50) had higher resistance to

permanent deformation as compared with the controlmixture. The mixtures modified by 10% fly ash by wt.of asphalt cement (60-70) had higher resistance topermanent deformation as compared with the control

mixture. The mixture modified by 3% sulfur by wt. ofasphalt cement (60-70) generally showed lowerresistance to permanent deformation as compared to

the other tested mixtures.

5. CONCLUSION

Based on the testing program, the following

conclusions may be drawn:(1) Asphalt Concrete Specimens containing 1%

fumed silica by wt. of asphalt cement (40-50) hadhigher stability value when compared to control mix.

On the other hand, the stability of mixtures containing3% sulfur by wt. of asphalt cement (60-70) was lowerthan those of control mixtures.

(2) The specimens containing 5% rubber by wt. ofasphalt cement (40-50) had the lowest air void

contents among the control mixtures and the othermixtures with different additives.

(3) The asphalt concrete mixtures modified by10% fly ash by wt. of asphalt cement (60-70) exhibithigh resistance to permanent deformation as comparedwith the control mixture.

(4) The mixture modified by 3% sulfur by wt. ofasphalt cement (60-70) generally showed lowerresistance to permanent deformation as compared to

the other tested mixtures.

REFERENCES

Ali N, Chan J, Simms S, Bushman R, Bergan A(1996). Mechanistic Evaluation of Fly AshAsphalt Concrete Mixtures. Journal of

Materials in Civil Engineering, ASCE, 8(1): 19-25, Technical paper.

Asi I, Assaad A (2005). Effect of Jordanian Oil ShaleFly Ash on Asphalt Mixes. Journal of Materialsin Civil Engineering, 553-559.

ASTM D-4123 (2002) Standard Test Method forIndirect Tension Test for Resilient Modulus of

Bituminous Mixtures. American Society ofTesting and Materials.

Bahia H, Hanson DI, Zeng M, Zhai H, Khatri M,Anderson R (2001). Characterization ofModified Asphalt Binder in Super-pave Mix

Design. TRB, NCHRP Report 459, NationalAcademy Press, Washington.


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Cooper SB, Mohammad LN, Elseifi M (2011).Laboratory Performance Characteristics ofSulfur-Modified Warm-Mix Asphalt. Journal ofMaterials in Civil Engineering, ASCE.

He Z, Lu Z, Zhang W (2010). Performance Study onRubber Powder Modified Asphalt of WasteTire. Integrated Transportation Systems Green.

Intelligent, ASCE.SCRB/R9 (2003). Standard Specification for Roads

and Bridges. Section R/9, Hot-Mix AsphaltConcrete Pavement, Revised Edition. State

Commotion of Roads and Bridges, Ministry ofHousing and Construction, Republic of Iraq.

Tara L (2003). Resilient Modulus of Asphalt ConcreteMixtures. M.Sc. Thesis, Civil Engineering,university of Manitoba, Manitoba, Canada.

Tayebali AA, Goodrich JL, Sousa JB, Monismith CL(1992). Influence of the Rheological Properties

of Modified Asphalt Binders on the LoadDeformation Characteristics of the Binder-Aggregate Mixtures. Polymer Modified AsphaltBinders, ASTM STP1108, American Societyfor Testing and Materials, Philadelphia, P. 78.


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Prof. Saad Issa Sarsamwas born in Baghdad 1955, got his BSc. In Civil Engineering (1977), Post

graduate 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 at

University of Mosul (1992-2005) and got the Assistant Professor degree at 2002; He joined theacademic 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).

Ibtihal M. Laftaawas born in Baghdad 1988, got her BSc. in Civil Engineering (2010); MSc. in

Civil Engineering (Transportation) in (2012).

Documents

Impact of Asphalt Additives on Rutting Resistance of Asphalt Concrete