research article performance evaluation of stone mastic...

Research ArticlePerformance Evaluation of Stone Mastic Asphalt and Hot MixAsphalt Mixtures Containing Recycled Concrete Aggregate

Mohammad Saeed Pourtahmasb and Mohamed Rehan Karim

Department of Civil Engineering, Center for Transportation Research (CTR), Faculty of Engineering, University of Malaya (UM),50603 Kuala Lumpur, Malaysia

Correspondence should be addressed to Mohammad Saeed Pourtahmasb; [email protected]

Received 1 June 2014; Revised 12 August 2014; Accepted 27 August 2014; Published 7 September 2014

Academic Editor: Sridhar Komarneni

Copyright © 2014 M. S. Pourtahmasb and M. R. Karim. This is an open access article distributed under the Creative CommonsAttribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work isproperly cited.

Environmental and economic considerations have encouraged civil engineers to find ways to reuse recycled materials in newconstructions. The current paper presents an experimental research on the possibility of utilizing recycled concrete aggregates(RCA) in stone mastic asphalt (SMA) and hot mix asphalt (HMA) mixtures. Three categories of RCA in various percentages weremixed with virgin granite aggregates to produce SMA and HMA specimens. The obtained results indicated that, regardless of theRCA particular sizes, the use of RCA to replace virgin aggregates increased the needed binder content in the asphalt mixtures.Moreover, it was found that even though the volumetric and mechanical properties of the asphalt mixtures are highly affected bythe sizes and percentages of the RCA but, based on the demands of the project and traffic volume, utilizing specific amounts ofRCA in both types of mixtures could easily satisfy the standard requirements.

1. Introduction

In recent years, many studies have been carried out on the useof construction and demolition (C&D) wastes in developedcountries.Themost considerable interest is the reuse of wastematerials in new construction sectors. It is the intentionof scientists and researchers, as well as people in authority,to explore waste material recycling for environmental andeconomic advantages and also the possibility of solid wastereuse in road construction [1]. Reusing waste material is oneof the many ways to solve the problem of excess solid wastematerials in industrial and urban areas. It can make signif-icant contributions to the environment and the economy,such as (1) reducing the overuse of natural resources andsaving them fromexhaustion, (2) reducing the environmentalpollution levels from waste materials generated in urban andindustrial areas, and (3) contributing to savings in energy andmoney. Therefore, in order to reduce their negative impactson the environment, it is logical to reuse these wastematerialsin engineering and industrial applications [2].

Recycled concrete aggregate (RCA) is produced bycrushing demolished concrete structures such as buildings,

bridges, and dams. RCAs were initially used as filler materialsand based on previous researches; it could be used as roadsubbase materials and in nonstructural concrete applicationssuch as curbs, canal lining, driveways, and footpaths [3–6].Waste materials to be used in pavement constructions cancome from different sources, including demolition of civilengineering structures and industrial wastes.These materialsare mostly classified based on their resources like industrialby-products (steel slag and coal fly ash), demolition by-products (concrete, tiles, and bricks), and road by-productssuch as RAP (recycled asphalt pavements) or RCP (recycledconcrete pavements) [7]. Concrete is themost basic construc-tion material all around the world, which essentially consistsof aggregates (sand, crushed stone, or gravel), cement, andwater. Environmental and economic considerations haveencouraged governments to find ways to use recycled mate-rials in new productions. When the concrete structure isdemolished, repaired, or renewed, recycling is an increasinglycommon method of reusing the rubble concretes. On theother hand, in recent years, the knowledge of continuedwholesale extraction and use of aggregates from naturalresources have been questioned at the international level.

Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2014, Article ID 863148, 12 pageshttp://dx.doi.org/10.1155/2014/863148

2 Advances in Materials Science and Engineering

This is the result of the depletion of quality primary aggre-gates and greater awareness on environmental protection.Moreover, the availability of natural resources for futuregenerations has also been considered as an important issue[8].

2. Use of RCA in Asphalt Mixtures

Waste material from demolished concrete structures is oneof the largest wastes in the entire world. For example, thisamount of waste in Europe is around 180million tons per yearor 480 kg per capita per year [9]. These ranges are from over700 kg per person in a year in Germany and the Netherlandsand 500 in UK to almost 200 in Greece, Sweden, and Ireland.Therefore, concrete waste has become a global concern thatrequires a sustainable solution [10]. Recent studies on RCAshave shown the acceptable potential to produce strong anddurablematerials for HMApavements. However, the amountof fine RCA should not exceed more than 30 percent ofthe fine aggregate portion of the pavement mixtures. Thisis because as the fine RCA increases, the density will bedecreased due to higher mortar in fines which causes higherwater absorption in the mixture [11]. In 2003, the FederalHighway Administration (FHWA) proved the acceptableperformance of RCA in base and subbase materials of roadswhich not only significantly reduce the costs but also havemany environmental benefits [12]. In latter investigation, in2004, California Department of Transportation (Cal-trans)discovered that even though the RCA collection startupscosts are high, in general, overhead costs are significantlyreduced [13]. Recycled concrete aggregates are different fromvirgin aggregates due to the amount of cement pastes remain-ing on the surface of the recycled aggregates after undergoingthe recycling process [14, 15]. The presence of cement pasteincreases the porosity of the aggregates, reduces the particledensity, and thus affects the quality and water absorptioncapacity of the RCA. Therefore, utilizing RCA in hot mixasphalt (HMA) mixtures affected the volumetric propertiesand performance of HMAmixtures [16].

In a joint experiment, Paranavithana andMohajerani [15]performed experiments on the effects of recycled concreteaggregates on the properties of HMA, in which 50% RCA bydry weight of total aggregates was used as coarse aggregatein the asphalt mixtures. The performance tests carried outon these mixes showed that using RCA in HMA mixtureslowered the resilient modulus and creep resistance of the mixand increased the stripping potential of them. In addition, themixes containing RCA showed large variations in strengthunder dry andwet conditions. In 2007,Wong et al. [11] studiedon the utilization of RCA as a partial aggregate substitutionin HMA. Three HMA mixes were included in the studyby substituting granite filler/fines with 6% untreated, 45%untreated, and 45% heat-treated recycled concrete, respec-tively. All three mixes passed the wearing course criteriaspecified by the Singapore Land Transport Authority (SLTA),based on the Marshall mix design method. The performancetests on the mix with 6% RCA showed comparable resilientmodulus and creep resistance to those of the traditionalHMA

mix. The mixes with the higher percentage of RCA showedhigher resilient modulus and resistance to creep.

Another research was conducted by Topal et al. [16]who studied the use of recycled concrete aggregates in hotmix asphalt. They found that RCA can substitute HMAaggregates and achieve the required Marshall stability (MS)and indirect tensile strength (IDT) of the mixtures. The testresults indicated that the Marshall stability values increasedwith the increase of RCA in the mix. However, the voids inmineral aggregate (VMA) and the voids filled with asphalt(VFA) decreased with the increase in RCA content. Thiswas believed to be due to crushing of RCA by the Marshallcompactor during compaction. The tensile strength of themix containing RCA was found to be higher than that of thecontrol mix as the internal friction of RCA was higher thanthat of natural limestone aggregates. Eventually, RCAwas notrecommended to be used in the wearing course due to RCA’ssusceptibility to abrasion by vehicles.

Mills-Beale and You [17] investigated the feasibility ofusing RCA for a low-volume traffic road in Michigan, with25%, 35%, 50%, and 75% of virgin aggregates by the weightof total aggregates substituted with RCA. It was found thatincreasing the RCA’s content decreased the VMA and VFAof the mixes. The laboratory test results indicated that allthe 4 mixes containing RCA passed the minimum ruttingspecification of 0.32 inch rut depth. Dynamic modulus testresults showed that the stiffness of the mixtures containingRCA was less than control mix, but using RCA in HMAmixtures reduced the energy needed for compaction. Interms of moisture susceptibility, all the mixes (except 75%RCA mix) passed the tensile strength ratio (TSR) of 80%.Based on the literatures, limited studies have been carried outon the usage of RCA in dense-graded (DG) asphalt mixtures.However, due to the success obtained by using RCA in HMA,it appears that there is a need to evaluate the use of RCA instonemastic asphalt (SMA)mixtures aswell. In this paper, thepossibility of usingRCA in SMAandHMAmixtures has beeninvestigated and the test results were tabulated and discussed.

3. Materials and Methods

3.1. Materials. Granite aggregates, 80/100 penetration gradebitumen, hydrated limestone powder, oil palm fiber, andrecycled concrete aggregates (RCA) were obtained for use inthis research. The crushed granite aggregates were providedfromKajang rock quarry (located near Kuala Lumpur, capitalof Malaysia). To provide the RCA, concrete infrastructureswere first demolished and crushed into large chunks.The steelbars were subsequently removed and the concrete debris wastransferred to a crusher machine to produce proper sizedaggregates. Bitumen, filler, and fibers (to be used in SMA)were obtained from the university materials supplier. Figures1 and 2 present the used aggregate gradation in this researchfor SMA and HMA mixtures based on the asphalt institute(AI) and ASTM D3515. Moreover, physical properties ofRCA, granite aggregates, and 80–100 binder are, respectively,outlined in Tables 1, 2, and 3.

Advances in Materials Science and Engineering 3

Table 1: Physical properties of RCA.

Test Method Value Standard requirementLA abrasion ASTM C131 24.5 Below 30%Aggregate impact value BS812: Part 3 11.31 Below 15%Aggregate crushing value BS812: Part 3 28.3 Below 30%Flakiness index BS812: Part 3 9.8 Below 20%Angularity number BS812: Part 3 8.40 Between 6 to 9Elongation index BS812: Part 3 5.35 Below 20%Sand equivalent AASHTO T176 65 Above 45%Water absorption (coarse) ASTM C 127-07 2.69 —Water absorption (fines) ASTM C 128-07 4.28 —Specific gravity (coarse) ASTM C 127-07 2.18 —Specific gravity (fine) ASTM C 128-07 2.42 —

Table 2: Physical properties of granite.

Test Method Value Standard requirementLA abrasion ASTM C131 18.3 Below 30%Aggregate impact value BS812: Part 3 6.21 Below 15%Aggregate crushing value BS812: Part 3 20.82 Below 30%Flakiness index BS812: Part 3 7.9 Below 20%Angularity number BS812: Part 3 6.31 Between 6 to 9Elongation index BS812: Part 3 8.10 Below 20%Polished stone value BS812: Part 3 50.75 Above 40Soundness BS812: Part 3 5.25 Below 12%Water absorption (coarse) ASTM C 127-07 0.44 —Water absorption (fines) ASTM C 128-07 1.11 —Specific gravity (coarse) ASTM C 127-07 2.61 —Specific gravity (fine) ASTM C 128-07 2.64 —

0102030405060708090100

0.01 0.1 1 10

Pass

ing

(%)

Sieve size (mm)

Upper limitLower limitDesired

Figure 1: SMA aggregate gradation based on the Asphalt Institute(2007).

3.2. Methods

3.2.1. Sample Preparation. In this study, SMA and HMAmixtures were compacted by using roller compactor and therequired specimens were cored out of the compacted slabsto evaluate the performance tests. 20%, 40%, 60%, and 80%

0102030405060708090100

0.01 0.1 1 10

Pass

ing

(%)

Sieve size (mm)

Upper limitLower limitDesired

Figure 2: HMA aggregate gradation based on ASTM D3515.

RCA were blended with virgin aggregates to produce theasphalt specimens. However, these percentages were dividedinto three categories comprising of coarse RCA (C-RCA), fineRCA (F-RCA), and a mix of both (M-RCA) with the virginaggregates (VA) based on the mentioned values. Also, the 0%


Table 3: Physical properties of 80/100 binder.

Test Method Value Standard requirementPenetration ASTM D5 84.7 84–95Softening point ASTM D36 47.2 47–49Flash point ASTM D92 289 275–302Fire point ASTM D92 303 >302Viscosity at 135∘C ASTM D4402 0.254 —Viscosity at 165∘C ASTM D4402 0.099 —Specific gravity ASTM D70 1.03 —

Table 4: SMA/HMA aggregate content.

VA (%) C-RCA F-RCA M-RCA

8020 — —— 20 —— — 20

6040 — —— 40 —— — 40

4060 — —— 60 —— — 60

2080 — —— 80 —— — 80

Table 5: Optimum asphalt content (OAC) of SMA and HMAmixtures.

Mix design OAC of SMA (%) OAC of HMA (%)100% VA 6.2 5.120% F-RCA 6.2 5.540% F-RCA 6.3 5.960% F-RCA 6.5 6.580% F-RCA 6.5 7.320% C-RCA 6.4 5.440% C-RCA 7.0 5.560% C-RCA 7.9 6.280% C-RCA 8.9 6.820% M-RCA 6.4 5.440% M-RCA 6.6 5.960% M-RCA 7.0 6.480% M-RCA 7.8 7.0

RCA mixture (100% VA mix) was performed as the controlmix. SMA andHMAaggregates content are shown in Table 4.

Marshall mix design method was used to measure theoptimum asphalt content (OAC) of SMA andHMAmixturesand results are displayed inTable 5. Tomake a better adhesionbetween aggregates and bitumen during the mix procedureand remove the excessive dusts from the surface of theRCAs, the crushed concretes were submerged, washed, andthen dried well before being used in the asphalt mixtures.The required amounts of aggregates, fillers, and RCA were

weighed and placed into the oven at 200∘C for 2 hours. Therequired quantity of 80/100 binder was weighed and heatedfor a period of 1 hour at 150∘C.

Hot aggregates (including RCA) were mixed with binderat 160 ± 5∘C until all the aggregates were coated. However, toprevent binder drain down (in SMAmixtures), the loose formfibers (0.3 percent by the weight of total mix) were blendedwith the hot aggregates before the binder being introduced.Finally, the weighed amount of filler was added and mixedwell. All the mixtures were conditioned for 4 hours at 150∘Cand then compacted with the target of 4% air voids content.

3.3. Marshall Tests

3.3.1. Density and Air Voids Tests. Bulk density was deter-mined in accordance with ASTM D2726. Bulk density wasmeasured by weighing in air and water using the followingequations:

𝑑 = 𝐺𝑚𝑏× 𝜌𝑤,

𝐺𝑚𝑏= [

𝑊𝐷

(𝑊SSD −𝑊SUB)] .

(1)

Air voids analysis was carried out in accordance with ASTMD 3203. The air voids value of the specimens was measuredusing the following equation with the value of calculatedtheoretical maximum density (TMD):

VTM = [1 − ( 𝑑TMD)] × 100, (2)

where 𝑑 = bulk density (g/cm3), 𝐺𝑚𝑏

is the bulk specificgravity of the mix, 𝐺

𝑠𝑏is the bulk specific gravity of the

aggregates, 𝜌𝑤is the density of water (g/cm3),𝑊

𝐷is themass

of specimen in air (g),𝑊SUB is the mass of specimen in water(g),𝑊SSD is the saturated surface dry mass (g), and VTM isthe voids in total mix.

3.3.2. Marshall Stability and Flow Tests. Marshal stabilityand flow tests were accomplished in accordance with ASTMD1559. The maximum load carried by a compacted SMAand HMA specimens at 140∘F (60∘C), with a loading rateof two inches per minute (50.8mm/min), was defined asMarshall stability. Also, the vertical deformation of theasphalt specimen at the same time of running the Marshallstability (measured from start of loading, until the stabilitybegins to decrease) was defined as flow.


3.3.3. Voids in Mineral Aggregates (VMA) and Voids Filledwith Asphalt (VFA) Tests. Voids in mineral aggregates(VMA) and voids filled with asphalt (VFA) were determinedby using the given equations:

VMA = 100 × {1 − [𝐺𝑚𝑏(1 − 𝑃

𝑏)

𝐺𝑠𝑏

]} ,

VFA = [(VMA − VTM)VMA

] × 100,

(3)

where 𝑃𝑏is the asphalt content, percent by the weight of the

mix, VMA is the voids inmineral aggregates, VFA is the voidsfilled with asphalt, and 𝑇

𝑅is the tracking rate.

3.4. Resilient Modulus (𝑀𝑅). The modulus of asphalt is an

essential parameter for designing flexible pavements duringthe application of the elastic-layered system theory. Overthe years, resilient modulus (𝑀

𝑅) test has been one of the

most popular tests for asphalt mixtures and is being used tomeasure the response of the asphaltic pavements to the actualwheel loads [18]. In this study, the material testing apparatus(MATTA) was used to determine the resilient modulus ofthe SMA and HMA specimens. This test was carried outin accordance with ASTM D4123 to apply indirect repeatedaxial pulses to the asphalt specimens at 25∘C and measuringthe horizontal deformations of the curved surface of thespecimens with two attached linear variable displacementtransducers (LVDTs). Each specimen was kept for at leasttwo hours at 25∘C (for conditioning) before starting the testand results were automatically recorded by using computersoftware based on the given equation:

𝑀𝑅=

𝑃

𝐻𝑡

(0.27 + 𝜇) , (4)

where𝑀𝑅is the resilient modulus (Psi), 𝑃 is the applied load

(pounds), 𝐻 is the total recoverable horizontal deformation(inches), 𝑡 is the sample thickness (inches), and 𝜇 is thePoisson’s ratio.

3.5. Loaded Wheel Tracking (LWT). Rutting resistance is oneof themost important and critical performance requirementsof asphalt mixtures and this role becomes more critical inhot climates. There are several tests used to evaluate ruttingof asphalt mixtures such as Marshall test, wheel track test,static and dynamic creep tests, and indirect tensile tests [19].Hence, due to the better field simulation, the wheel trackingtest is the most commonly recommended test [20]. Loadedwheel tracking (LWT) test was conducted in accordance withBritish Standard (BS 598-110) to determine thewheel trackingrate and depth at 45∘C for the moderate to heavily stressedsites. Table 6 presents the maximum allowable rut depth andrut rate values of asphalt mixtures at 45 and 60∘C.

In the present study, 78 SMAand 78HMAcore specimens(72 specimens containing RCA and 6 specimens as a controlmix, made of virgin aggregates) with 200mm diameter werecored out from fabricated slabs. Each core specimen waspreconditioned at 45∘C for 6 hours before starting the actualtest. The loading wheel was set in motion to reciprocate

over the specimen at the rate of 21 cycles per minute. The520 ± 5N load was applied to the surface of the specimenthrough a 50mm width moving wheel, and the rut depthvalue was recorded every 5 minutes (105 cycles). The testwas continued for 45 minutes or until 15mm deformationoccurred in the specimen (whichever comes first). Trackingrate (𝑇

𝑅) and wheel tracking rate (𝑊TR) were defined using

the given equations:

𝑇𝑅= 3.6 (𝑟

(𝑛)− 𝑟(𝑛−3)) + (𝑟(𝑛−1)− 𝑟(𝑛−2)) ,

𝑊TR = 10.4 × 𝑇𝑅𝑀 ×𝜔

𝐿

,

(5)

where 𝑟𝑛is the depth measurement at 𝑛th reading, 𝑊TR is

the wheel tracking rate, 𝑇RM is the mean value of 𝑇𝑅, 𝜔 is the

width of wheel’s contact area, and 𝐿 is the total load.

4. Results and Discussion

4.1. Marshall Tests

4.1.1. Density and Air Voids Tests. Figure 3 displays the resultsof comparison between the influence of RCA on the densityand VTM (voids in total mix) values of SMA and HMAspecimens. The measured density values of SMA and HMAmixtures containing 100% virgin granite aggregates (VA)were 2.314 and 2.438 kg/cm3. Test results indicated that thedensity values of SMA and HMA mixtures decreased withincreasing RCA content due to the lower specific gravity anddensity of RCA (compared to granite), except 20 and 40% F-RCA-SMA in which density values slightly increased.

In terms of air voids, the SMA and HMA specimens wereproduced and compactedwith the target of 4%VTMcontent.The calculated VTM values indicated that, regardless of theRCA content in the SMA and HMA asphalt mixtures, the airvoids could be easily controlled. SMA specimens containing80% C-RCA and 80% M-RCA showed slightly higher VTMvalues compared to the other asphalt specimens which couldbe due to the breaking of the C-RCA during compaction.

4.1.2. Marshall Stability and Flow Tests. Regardless of theamount of RCA content in asphalt mixtures, the Marshallstability (MS) values of the HMA specimens were foundconsiderably higher than SMA specimens due to its densegradation of the aggregates. The calculated Marshall stability(MS) values for SMA and HMA mixtures containing 100%VA were 10.63 and 14.63 KN. Figure 4 displays the MSand flow values of SMA and HMA mixtures containingdifferent percentages of RCA content. Test results indicatedthat 20% and 40% F-RCA could increase the MS valuesof SMA mixtures up to 10.66 and 10.77 KN. Flow valuesin both types of asphalt mixtures slightly increased withincreasing RCA content, but at 80% C-RCA and M-RCAin the SMA and 80% F-RCA and M-RCA in the HMAspecimens the flow values increased significantly. Accordingto the Asphalt Institute (AI), the minimum stability valuesof SMA and HMA are expected to be 6.2 and 9KN. Theinfluence of F-RCA in SMA and C-RCA in HMA mixtureswas not too much considerable, but as the amount of C-RCA


Table 6: British Standard requirements (BS 598-110).

Description Test temperature (∘C) Max rut rate (mm/hr) Max rut depth (mm)Moderate to heavily stressed sites requiring high rut resistance 45 2 4Very heavily stressed sites requiring very high rut resistance 60 5 7

2.200

2.220

2.240

2.260

2.280

2.300

2.320

2.340

0 20 40 60 80 100RCA content (%)

Den

sity

(gr/

cm3)

(a)

3.80

3.85

3.90

3.95

4.00

4.05

4.10

4.15

4.20

0 20 40 60 80 100

VTM

(%)

RCA content (%)

(b)

2.2802.3002.3202.3402.3602.3802.4002.4202.4402.460

0 20 40 60 80 100RCA content (%)

F-RCAC-RCAM-RCA

Den

sity

(gr/

cm3)

(c)

3.803.853.903.954.004.054.104.154.20

0 20 40 60 80 100

VTM

(%)

RCA content (%)

F-RCAC-RCAM-RCA

(d)

Figure 3: (a) Density of SMA specimens. (b) Air voids of SMA specimens. (c) Density of HMA specimens. (d) Air voids of HMA specimens.

and M-RCA in SMAmixtures increased to 80%, the stabilityvalues decreased to 5.23 and 5.77 KN which are below theAI specification. In HMAmixtures, almost all the specimensperformed the acceptable values in terms of stability exceptfor 80% F-RCA and M-RCA in which the stability decreasedto 7.91 and 8.4 KN, respectively.

4.1.3. Voids in Mineral Aggregates (VMA) and Voids Filledwith Asphalt (VFA) Tests. In the asphalt mixtures containing100%VA, the calculated values of voids in mineral aggregates(VMA) and voids filled with asphalt (VFA) were 15.55 and73.91% in SMA and 15.44 and 73.64% in HMA mixtures.Test results indicated that, as the amount of RCA increasedin asphalt mixtures, the VMA and VFA values increased aswell (Figure 5). It is believed that the higher porosity andabsorption of the RCA compared to VA lead to higher OAClevels and caused the mentioned behaviors in the asphaltmixtures. According to theAI, theminimumacceptable value

of VMA is dependent on the nominal maximum aggregatesize of the mixtures and desired air voids level. The nominalmaximum aggregate sizes of HMA and SMA mixtures were9.5 and 12.5mm and the desired air void level was 4% for bothmixtures. Therefore, the allowable VFA values for asphaltspecimens are expected to be from 65% to 78% for mediumtraffic volume and from 70% to 80% for heavy traffic volume.Also, the minimum VMA values for HMA and SMA are 15%and 14%. Test results revealed that all the SMA and HMAspecimens could meet desired values in terms of VMA andVFA.

4.2. Resilient Modulus (𝑀𝑅). Figure 6 presents the resilient

modulus (𝑀𝑅) of the SMA and HMA mixtures containing

RCA. The 𝑀𝑅values of the SMA and HMA mixtures con-

taining RCA were lower than VA mixtures and reduced withany increase in RCA content. SMA specimens containing20 and 40% F-RCA showed higher values compared to VA


4

5

6

7

8

9

10

11

12

0 20 40 60 80 100

Stab

ility

(KN

)

RCA content (%)

(a)

0

1

2

3

4

5

6

7

8

0 20 40 60 80 100

Flow

(mm

)

RCA content (%)

(b)

456789

101112131415

0 20 40 60 80 100

Stab

ility

(KN

)

RCA content (%)

F-RCAC-RCAM-RCA

(c)

0

1

2

3

4

5

6

7

8

0 20 40 60 80 100

Flow

(mm

)

RCA content (%)

F-RCAC-RCAM-RCA

(d)

Figure 4: (a) Stability of SMA specimens. (b) Flow of SMA specimens. (c) Stability of HMA specimens. (d) Flow of HMA specimens.

specimens and the 𝑀𝑅values slightly increased up to 2860

and 2906Mpa while the 𝑀𝑅values of VA-SMA and VA-

HMA were 2814 and 3119Mpa, respectively. According tothe standards, the minimum value for resilient modulusof wearing course in conventional flexible pavements isexpected to be 2100Mpa. The measured values of resilientmodulus in HMA and SMA mixtures indicated that all thespecimens could fulfill the minimum requirement exceptSMA specimens containing 80% C-RCA and 80% M-RCA.It is believed that the considerable reduction in𝑀

𝑅values by

increasing the coarse RCA content in the SMA mixtures aredue to the higher amounts of coarse aggregates in SMA incomparison to HMAmixtures.

4.3. Wheel Tracking Depth. Figure 7 illustrates the loadedwheel tracking test results and the effect of C-RCA on SMAand HMA specimens in terms of permanent deformation.The rut depth values for SMA mixtures with 0, 20, 40, 60,and 80% C-RCA content during 45 minutes were 1.65, 2.52,3.63, 4.46, and 6.17mm, respectively. Moreover, the rut depthvalues for HMA mixtures containing the same amount of

C-RCA content were 2.90, 2.91, 3.00, 4.09, and 6.33mm. Asthe C-RCA content increased from0% (VAmix) to 20, 40, 60,and 80%, the values of rut depth increased by 52.7, 120, 170.3,273.9% in SMA and by 0.34, 3.45, 41.03, and 118.27% in HMAspecimens. It was found that the influence of C-RCA in SMAspecimens was considerably higher than HMAmixtures.

Figure 8 demonstrates the rut depth values of the SMAand HMA specimens containing F-RCA. SMAmixtures with0, 20, 40, 60, and 80% F-RCA showed 1.65, 1.60, 1.41, 2.97,and 3.28mm rut depths and HMA specimens showed 2.90,2.96, 3.31, 4.47, and 7.08mm rut depths during 45 minutes.The achieved results indicated that, as the F-RCA contentraised from 0 to 80% in HMAmixtures, the rut depth valuesincreased up to 2.07, 14.14, 54.14, and 144.14%, respectively.However, the rut depth values of SMAmixtures reduced from1.65mm in VA-SMA to 1.6 and 1.41mm in 20 and 40% F-RCA and then increased up to 2.97 and 3.28mm in 60 and80% F-RCA. Based on the test results, up to 40% F-RCAhad a positive effect on the rutting of SMA mixtures. It wasbelieved that the higher density andMS values (Figures 3 and4) of SMA specimens containing 20 and 40% F-RCA causedthe better resistance in terms of rutting.


15.0

15.5

16.0

16.5

17.0

17.5

0 20 40 60 80 100

VM

A (%

)

RCA content (%)

(a)

73.5

74.0

74.5

75.0

75.5

76.0

76.5

0 20 40 60 80 100

VFA

(%)

RCA content (%)

(b)

15.0

15.5

16.0

16.5

17.0

17.5

18.0

0 20 40 60 80 100

VM

A (%

)

RCA content (%)

F-RCAC-RCAM-RCA

(c)

74.0

74.5

75.0

75.5

76.0

76.5

77.0

77.5

0 20 40 60 80 100

VFA

(%)

RCA content (%)

F-RCAC-RCAM-RCA

(d)

Figure 5: (a) VMA of SMA specimens. (b) VFA of SMA specimens. (c) VMA of HMA specimens. (d) VFA of HMA specimens.

1,600

1,800

2,000

2,200

2,400

2,600

2,800

3,000

3,200

3,400

0 20 40 60 80 100

Resil

ient

mod

ulus

(MPa

)

RCA content (%)

F-RCAC-RCAM-RCA

(a)

1,600

1,800

2,000

2,200

2,400

2,600

2,800

3,000

3,200

3,400

0 20 40 60 80 100

Resil

ient

mod

ulus

(MPa

)

RCA content (%)

F-RCAC-RCAM-RCA

(b)

Figure 6: (a) Resilient modulus of SMA specimens. (b) Resilient modulus of HMA specimens.


0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

0 5 10 15 20 25 30 35 40 45 50

Rut d

epth

(mm

)

Time (min)

VA-SMA 20% RCA

40% RCA60% RCA 80% RCA

(a)

Time (min)

VA-HMA 20% RCA


0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

0 5 10 15 20 25 30 35 40 45 50

Rut d

epth

(mm

)

(b)

Figure 7: (a) Effect of C-RCA on rut depth of SMA specimens. (b) Effect of C-RCA on rut depth of HMA specimens.

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

0 5 10 15 20 25 30 35 40 45 50

Rut d

epth

(mm

)

Time (min)

VA-SMA 20% RCA


(a)

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

0 5 10 15 20 25 30 35 40 45 50

Rut d

epth

(mm

)

Time (min)

VA-HMA 20% RCA


(b)

Figure 8: (a) Effect of F-RCA on rut depth of SMA specimens. (b) Effect of F-RCA on rut depth of HMA specimens.

The rut depth values of SMA and HMA specimenscontaining M-RCA are shown in Figure 9. The obtained testresults indicated that the rut depth values of SMA and HMAspecimens containing M-RCA were lower than the controlmixes and any further increase in RCA content into theasphalt mixtures increased the values of rut depth. Based onthe BS requirement the maximum allowable value of the rutrate at 45∘C was 4mm (Table 6). Even though the majority ofthe rut depth values was increased by utilizing RCA in bothSMA and HMAmixtures, most of the specimens could fulfillthe standard requirement in terms of rut depth except 60 and80% C-RCA and M-RCA in SMA mixtures and 80% C-RCAand M-RCA and 60, 80% F-RCA in HMA.

4.4. Wheel Tracking Rate. The wheel tracking rate 𝑊TR isthe second important factor which should be considered in

rutting studies. The calculated wheel tracking rate (𝑊TR) forcontrol mixtures (0% RCA) showed 0.34mm/hr for SMAand 0.40mm/hr for HMA. The rut rate values of SMA andHMA mixtures containing various amounts of RCA aredisplayed in Figure 10. Regardless of the amounts of utilizedRCA content in the asphalt mixtures, the rut rate values ofHMA were found considerably higher than SMA specimens.However, the calculated rut rate values of all the specimenswere below 2mm/hr (BS requirement) except 60 and 80% C-RCA in SMA specimens in which rut rate values increased upto 2.05 and 2.16mm/hr. Generally, the mixtures containinghigher amount of RCA showed higher values in terms ofrut rate. However, there was no considerable change betweenVA-SMA compared to 20 and 40% F-RCA and VA-HMAcompared to 20 and 40% C-RCA but as the amount of RCAincreases from 40 to 60 and 80% the rut rate growth became


0.00

1.00

2.00

3.00

4.00

5.00

6.00

0 5 10 15 20 25 30 35 40 45 50

Rut d

epth

(mm

)

Time (min)

VA-SMA 20% mix

40% mix60% mix 80% mix

(a)

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

0 5 10 15 20 25 30 35 40 45 50

Rut d

epth

(mm

)

Time (min)

VA-HMA 20% RCA


(b)

Figure 9: (a) Effect of M-RCA on rut depth of SMA specimens. (b) Effect of M-RCA on rut depth of HMA specimens.

20%

C-R

CA

40%

C-R

CA

60%

C-R

CA

80%

C-R

CA

20%

F-R

CA

40%

F-R

CA

60%

F-R

CA

80%

F-R

CA

20%

M-R

CA

40%

M-R

CA

60%

M-R

CA

80%

M-R

CA

0.00

0.50

1.00

1.50

2.00

2.50

Rut r

ate (

mm

/hr)

VA

(a)

20%

C-R

CA

40%

C-R

CA

60%

C-R

CA

80%

C-R

CA

20%

F-R

CA

40%

F-R

CA

60%

F-R

CA

80%

F-R

CA

20%

M-R

CA

40%

M-R

CA

60%

M-R

CA

80%

M-R

CAVA

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

Rut r

ate (

mm

/hr)

(b)

Figure 10: (a) Rut rate values of SMA mixtures including RCA content. (b) Rut rate values of HMAmixtures including RCA content.

more significant. This behavior can be attributed to the highamount of fines and low amount of coarse aggregates inHMAbut the SMA aggregate gradation is vice versa.

5. Analysis of Variance

The objective of this research was to evaluate the volumetricand mechanical properties of stone mastic asphalt and hotmix asphalt mixtures containing recycled concrete aggre-gates. For this purpose, the performance of SMA and HMAmixtures containing various percentages of RCA has beenevaluated based on experimental tests. However, to comparethe differences among methods for research variables, theoutcomes were statistically analyzed and the determinationof the significance at certain confidence limits was per-formed with one-way analysis of variance (ANOVA). Prior

to data analysis, all the data were subjected to normality test.The results revealed that all the variables were distributednormally and the homogeneity test result indicated thatthe variances were homogenous. The significance level (𝛼)employed in this investigation was assumed to be 0.05. Tables7 and 8 present the variance analysis of SMA and HMAmixtures, respectively.

The results of ANOVA showed that all the measured𝑃 values were smaller than the significance level (𝛼) whichindicated that the role and effect of various percentages ofRCA in SMA andHMAmixtures were significantly different.

6. Conclusions

This paper has presented some of the experimental resultsobtained from the influence of recycled concrete aggregate


Table 7: ANOVA outcomes for SMA test results.

Tests SS MS 𝐹 𝑃 valueOAC 25.059 2.088 9.44 <0.01Stability 151.35 12.612 81.779 <0.01Flow 84.714 7.06 325.708 <0.01Density 0.051 0.004 181.1 <0.01VTM 0.094 0.008 6.163 <0.01VMA 11.539 0.962 228.397 <0.01VFA 23.068 1.922 32.35 <0.01Resilient modulus 5813509.59 484459.1 217.121 <0.01Rut depth 161.43 13.452 91561.39 <0.01Rut rate 28.854 2.405 8863.566 <0.01

Table 8: ANOVA outcomes for HMA test results.

Tests SS MS 𝐹 𝑃 valueOAC 17.387 1.449 5.883 <0.01Stability 159.723 13.31 122.565 <0.01Flow 58.083 4.84 90.755 <0.01Density 0.073 0.006 84.631 <0.01VTM 0.088 0.007 6.972 <0.01VMA 17.833 1.486 89.263 <0.01VFA 32.013 2.668 36.321 <0.01Resilient modulus 4502850 375237.5 144.752 <0.01Rut depth 134.489 11.207 87945.32 <0.01Rut rate 4.777 0.398 1587.373 <0.01

(RCA) on the performance of stone mastic asphalt (SMA)and hot mix asphalt (HMA) and the following conclusionsare obtained.

(i) The attached excessive cements to the surface of theRCA could increase the bitumen absorption in theasphalt mixtures and reduce the adhesion betweenRCA and binder. During the experimental tests itwas found that submerging and washing RCA beforebeing utilized in the asphalt mixture could consider-ably increase the performance of the HMA and SMAmixtures.

(ii) RCA has a porous structure, with lower specificgravity and higher absorption in comparison withvirgin aggregates.While the amounts of coarse aggre-gates are considerably higher in SMA mixtures, anyreplacement of VA coarse aggregates with C-RCAcan highly affect the mixture performance due tolower density and C-RCA fracture under pressure.Moreover, in HMA, due to higher amount of finescompared to coarse aggregates, any replacement ofVA fines with F-RCA causes a higher demand ofasphalt contents and reduces the density values of themixtures, which affect the HMA performance.

(iii) The technical basis of SMA is a stone skeleton withstone-on-stone contact which resists the shear forcescreated by applied loads and results in higher resis-tance to rutting. Regardless of the RCA sizes, thegrowth trend of rut depth and rut rate values in

the asphalt mixtures containing 20 and 40% RCA isconsiderably lower than 60 and 80% and as the levelof RCA increased up to 60 and 80%, the level of rutresistance reduction became more significant.

(iv) Even though utilizing RCA in asphalt mixtures couldaffect the volumetric andmechanical properties of themixtures, but based on the demands of the projectand traffic volume, using specific amounts of RCAin SMA and HMA mixtures can easily satisfy thestandard requirements. These findings can promotethe reuse and recycling of waste materials, especiallyRCA, in pavement industries to generate economicand environmental benefits in the future.

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper.

Acknowledgments

The authors would like to acknowledge the Center ofResearch Grant Management, Institute of Research Manage-ment and Monitoring of University of Malaya (UM), for thefinancial support of this project (Project no. ER030/2011A).


References

[1] Y. Xue, H. Hou, S. Zhu, and J. Zha, “Utilization of municipalsolid waste incineration ash in stone mastic asphalt mixture:pavement performance and environmental impact,” Construc-tion and Building Materials, vol. 23, no. 2, pp. 989–996, 2009.

[2] L. P. T. L. Fontes, G. Triches, J. C. Pais, and P.A.A. Pereira, “Eval-uating permanent deformation in asphalt rubber mixtures,”Construction and Building Materials, vol. 24, no. 7, pp. 1193–1200, 2010.

[3] M. C. Arm, “Self-cementing properties of crushed demolishedconcrete in unbound layers: results from triaxial tests and fieldtests,” Journal of Waste Management, vol. 21, no. 3, pp. 235–239,2001.

[4] W. L. Huang, D. H. Lin, N. B. Chang, and K. S. Lin, “Recyclingof construction and demolition waste via a mechanical sortingprocess,”Resources, Conservation andRecycling, vol. 37, no. 1, pp.23–37, 2002.

[5] C. McGrath, “Waste minimisation in practice,” Journal ofResources Conservation and Recycling, vol. 32, no. 3-4, pp. 227–238, 2001.

[6] U.-M. Mroueh and M. Wahlstrom, “By-products and recycledmaterials in earth construction in Finland—an assessment ofapplicability,” Resources, Conservation and Recycling, vol. 35, no.1-2, pp. 117–129, 2002.

[7] K.A. Pihl andO.Milvang-Jensen, “Themotivation factors in thedevelopment and sustainment of a well-functioning recyclingindustry for road and non-road byproducts in Denmark,” inProceedings of the Specialty Conference on Beneficial Use ofRecycled Materials in Transportation Applications, pp. 19–27,University of New Hampshire, Arlington, Va, USA, November2001.

[8] C. S. Poon, Z. H. Shui, L. Lam, H. Fok, and S. C. Kou,“Influence of moisture states of natural and recycled aggregateson the slump and compressive strength of concrete,” Cementand Concrete Research, vol. 34, no. 1, pp. 31–36, 2004.

[9] Aggregates advisory service-UK, “Construction and demolitionwaste management practices and their economic impacts,”Study for DGXI- European commission Digest 16, 1999.

[10] CSIR, “Reusing construction and demolition waste,” Buildingand Construction Technology, Techno Brief, 2000.

[11] Y. D. Wong, D. D. Sun, and D. Lai, “Value-added utilisationof recycled concrete in hot-mix asphalt,” Journal of WasteManagement, vol. 27, no. 2, pp. 294–301, 2007.

[12] FHWA, Summary of California recycled concrete aggregatereview. U.S. department of transportation. Federal HighwayAdministration, 2003, http://www.fhwa.dot.gov/pavement/recycling/rcaca.cfm.

[13] Focus, “Recycled concrete study identifies current uses bestpractices,” U.S. department of transportation, Federal HighwayAdministration, Publication no. FHWA-HRT-04-024, 2004,http://www.tfhrc.gov/FOCUS/apr04/01.htm.

[14] A. M. Schutzbach, “Case study of a full-depth asphalt concreteinlay,” Transportation Research Record 1337, Flexible Pave-ment Construction, Performance and Recycling, Transporta-tion Research Board, National Research Council, Washington,DC, USA, 1992.

[15] S. Paranavithana and A. Mohajerani, “Effects of recycled con-crete aggregates on properties of asphalt concrete,” Resources,Conservation and Recycling, vol. 48, no. 1, pp. 1–12, 2006.

[16] A. Topal, A. U. Ozturk, and B. Baradan, “Use of recycledconcrete aggregates in hot-mix asphalt,” in Proceeding of 8th

CANMET/ACI International Conference on Recent Advances inConcrete Technology, vol. SP- 235-20, pp. 282–295, AmericanConcrete Institute, Quebec, Canada, June 2006.

[17] J. Mills-Beale and Z. You, “Themechanical properties of asphaltmixtures with recycled concrete aggregates,” Construction andBuilding Materials, vol. 24, no. 3, pp. 230–235, 2010.

[18] E. Ahmadinia, M. Zargar, M. R. Karim, and M. Abdelaziz,“Performance evaluation of utilization of waste polyethyleneterephthalate (PET) in stone mastic asphalt,” Journal of Con-struction and Building Materials, vol. 36, pp. 984–989, 2012.

[19] S. Tayfur, H. Ozen, and A. Aksoy, “Investigation of rutting per-formance of asphalt mixtures containing polymer modifiers,”Journal of Construction and BuildingMaterials, vol. 21, no. 2, pp.328–337, 2007.

[20] X. Lu and P. Redelius, “Effect of bitumenwax on asphaltmixtureperformance,” Construction and Building Materials, vol. 21, no.11, pp. 1961–1970, 2007.

Submit your manuscripts athttp://www.hindawi.com

ScientificaHindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation http://www.hindawi.com Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation http://www.hindawi.com Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials

research article performance evaluation of stone mastic...

Documents