The Use of Glass to Optimize Bitumen Absorption of Hot Mix Asphalt Containing Recycled Construction Aggregates

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Article The Use of Glass to Optimize Bitumen Absorption of Hot Mix Asphalt Containing Recycled Construction Aggregates

Farzaneh Tahmoorian 1,*, Bijan Samali 1, John Yeaman 2 and Russell Crabb 3 1 Centre for Infrastructure Engineering, Western Sydney University, Penrith, NSW 2751, Australia; [email protected] 2 Faculty of Science, Health, Education and Engineering, University of Sunshine Coast, Sippy Downs, QLD 4556, Australia; [email protected] 3 Asphalt, Boral Ltd., North Ryde, NSW 2113, Australia; [email protected] * Correspondence: [email protected]

Received: 19 May 2018; Accepted: 13 June 2018; Published: 21 June 2018

Abstract: Asphalt mixtures containing recycled construction aggregates (RCA) have the problem of high bitumen absorption. This paper characterizes the effects of glass on the bitumen absorption and volumetric properties of asphalt mixtures containing 25% and 50% RCA through laboratory investigation. The materials used in the test program include C320 bitumen, RCA and recycled glass. Three glass contents of 0%, 10%, and 20% in terms of the total weight of ﬁne aggregates are used in the mixture designs for preparing 100 mm diameter specimens containing 0%, 25% and 50% RCA, under 120 gyration cycles. Different types of tests including aggregate speciﬁcation tests and volumetric analysis tests were conducted on individual aggregates and asphalt mixtures in accordance with Australian standards. The test results indicate that the glass waste can be a viable material for improving the problem of high bitumen absorption of asphalt mixtures containing RCA.

Keywords: asphalt; glass; recycled construction aggregate; volumetric properties; binder ﬁlm index

1. Introduction Waste materials are generated increasingly with the continuous growth in the economy and as consumption increases. The growing quantities of waste materials, lack of natural resources and shortage of landfill spaces represent the importance of finding innovative ways of reusing and recycling waste materials. Due to the large quantities of construction and demolition waste (CDW), recycling and utilization of Recycled Construction Aggregates (RCA) obtained from CDW in construction projects, including asphalt pavement construction, can be the most promising solution to this problem. Utilization of RCA in asphalt mixtures is a sustainable technology due to the important role and high portion of aggregates in asphalt mixtures. In addition, RCA has better characteristics for Flakiness Index and Particle Shape compared to basalt [1]. Since these two characteristics substantially influence the stability and strength of asphalt mixture [2], they can be considered as one of the strong points of RCA. However, the major drawback of RCA is its high water absorption compared to conventional aggregates which subsequently results in high bitumen absorption of asphalt mixtures containing RCA. By combining materials with low absorption, such as glass, the high bitumen absorption of asphalt mixtures containing RCA can be compensated. Using waste glass in RCA-contained asphalt mixtures reduces not only bitumen absorption but also the adverse environmental impacts associated with waste glass disposal due to the nonmetallic and inorganic nature of glass waste, which makes it impossible to be disposed in incinerators or sanitary landfills. In addition, the demand reduction for virgin aggregates is another advantage resulting in subsequent economic advantages.

Materials 2018, 11, 1053; doi:10.3390/ma11071053 www.mdpi.com/journal/materials Materials 2018, 11, x FOR PEER REVIEW 2 of 25

associated with waste glass disposal due to the nonmetallic and inorganic nature of glass waste, which makes it impossible to be disposed in incinerators or sanitary landfills. In addition, the Materialsdemand2018 reduction, 11, 1053 for virgin aggregates is another advantage resulting in subsequent economic2 of 25 advantages. However, developing a suitable mix design containing RCA and glass is necessary before employingHowever, this developingtechnology ain suitableasphalt mixmixture design prod containinguction. The RCA purpose and glassof the ispresent necessary work before is to employingstudy the benefit this technology of glass addition in asphalt on the mixture bitume production.n absorption The of asphalt purpose mixtures of the presentcontaining work RCA is toin studyorder theto optimize benefit of the glass RCA-contained addition on theasphalt bitumen mix absorptiondesign. In that of asphalt sense, mixturesas discussed containing in the RCAfollowing in order sections, to optimize severalthe tests RCA-contained were conducted asphalt on individual mix design. aggregates In that sense,in order as to discussed obtain further in the followingknowledge sections, on the recycled several testsaggregate were conductedproperties as on well individual as to compare aggregates them in with order the to corresponding obtain further knowledgeproperties of on the the recycledvirgin aggregate aggregate and properties the stan asdards well asrequirements. to compare themBased with on thethe correspondingresults of the propertiesaggregate ofspecification the virgin aggregate tests, different and the tests standards were conducted requirements. on asphalt Based onmixtures the results containing of the aggregate various specificationcombinations tests, of natural different and tests recycled were conducted aggregates on asphalt in order mixtures to investigate containing their various performance combinations in ofasphalt natural mixture and recycled and to aggregatescharacterize in the order effects to investigate of glass on their the performancebitumen absorption in asphalt and mixture volumetric and toproperties characterize of asphalt the effects mixtures of glass containing on the bitumen different absorption percentages and volumetric of RCA. propertiesThe findings of asphaltof the mixturesexperimental containing work differentare given percentages in three ofmain RCA. sections The findings including of the experimentalthe mechanical work and are physical given in threeproperties main of sections coarse includingaggregates the (i.e., mechanical RCA and and basalt), physical the physical properties characteristics of coarse aggregates of fine aggregates (i.e., RCA and(i.e., basalt),glass and the basalt) physical andcharacteristics volumetric performance of fine aggregates of Hot Mix (i.e., Asphalt glass and (HMA) basalt) containing and volumetric RCA in performancecombination ofwith Hot glass Mix Asphaltand without (HMA) glass. containing Figure RCA1 illustrates in combination the flowchart with glass of discussion and without in glass. this Figureresearch1 illustrates work. the flowchart of discussion in this research work.

Figure 1. The flowchart ﬂowchart of discussion in this research work.work.

2. Background Today, manymany waste waste materials materials such such as as tyres, tyres, plastics, plastics, waste waste glass, glass, etc. etc. are are used used for for construction construction of differentof different layers layers of pavements of pavements including including the asphalt the asphalt surface surface layer [layer3–14]. [3–14]. Utilization Utilization of solid of wastes solid inwastes the asphalt in the layerasphalt not layer only reducesnot only the reduces adverse the impacts adverse of impacts waste disposal of waste but disposal also the but demand also the for naturaldemand materials for natural which materials will subsequently which will results subsequently in cost savings results and economicin cost savings advantages. and Moreover,economic usingadvantages. the recycled Moreover, materials using inthe the recycled asphalt materials surface layerin the can asphalt contribute surface to layer more can improvement contribute ofto engineeringmore improvement characteristics of engineering of the asphalt characteristics pavement of materials, the asphalt representing pavement a ma value-addedterials, representing application a forvalue-added solid wastes. application However, for the solid selection wastes. of wasteHowever, materials the selection used for roadof waste construction, materials particularly used for road the surfaceconstruction, course, particularly is of high importance the surface ascourse, the incorporation is of high importance of wastes shouldas the notincorporation affect the functionalof wastes andshould structural not affect aspects the functional of the pavements and structural [15–17 ].aspects of the pavements [15–17]. In addition,addition, due to the importanceimportance of thethe aggregatesaggregates inin asphaltasphalt concrete,concrete, the studiesstudies on thethe utilization ofof the the recycled recycled aggregates aggregates such assuch reclaimed as reclaimed asphalt pavementasphalt pavement (RAP), recycled (RAP), construction recycled aggregateconstruction (RCA), aggregate recycled (RCA), glass, recycled etc. have glass, increased etc. have worldwide increased over worldwide the past two over decades the past [18 –two20]. Amongdecades the[18–20]. recycled Among aggregates, the recycled the large aggregates, amount th ofe construction large amount and of demolitionconstruction waste and generationdemolition worldwidewaste generation justiﬁes worldwide the idea of justifies using RCA the idea in new of using asphalt RCA mixtures. in new Referring asphalt mixtures. to available Referring literature to e.g., [21–28], RCA has been used in the base course and subbase course of pavements over the last two decades. However, few research studies [29–36] have reported the utilization of RCA in HMA. Materials 2018, 11, 1053 3 of 25

According to comprehensive aggregate specification tests on RCA, RCA cannot satisfy aggregate requirements for asphalt mixtures for two properties of water absorption and wet/dry strength variation [37]. Accordingly, the application of RCA without any virgin aggregates may result in asphalt mixtures with less efficiency. Therefore, it is required to consider the combination of RCA with other aggregates in certain percentages for the asphalt mixture design. Accordingly, some other materials such as recycled glass can be considered to compensate RCA for some of its shortcomings, and this research will seek for the optimum combination of these materials. In Australia, about 850,000 tonnes of glass are consumed, of which only 350,000 tonnes are recycled [38]. This means that approximately 500,000 tonnes of glass are disposed into the landfill every year. The Australian example is indicative of the glass waste disposal throughout the world. Using waste glass in combination with RCA in asphalt mixture provides substantial environmental and economic advantages since glass waste is one of the most important and particularly troublesome components of solid waste because it cannot be incinerated or degraded. Therefore, it is required to consider a proper approach for its management. Recycling is the most common method for handling glass wastes. In fact, glass can be recycled without any loss in the product quality. Recycling the glass wastes will result in substantial savings of energy as well as mineral resources. In addition, the recycling of glass helps to alleviate the increasing cost of landfill disposal [39]. However, the variations in glass colour have encouraged the authorities to seek alternative approaches to glass waste management. Many countries such as the United States, Japan, and several European countries have used glass waste as a substitution for fine aggregate in asphalt mixtures [40]. However, glass as aggregate in asphalt concrete should meet some technical specifications. Accordingly, many researchers [41–43] have studied the utilization of glass as aggregate for asphalt mixtures. Arabani and Azarhoosh (2011) studied the behaviour of asphalt mixtures containing glass (glassphalt) at different temperatures and by using different sizes of glass at different rates. The results of this investigation revealed that adding glass will improve the dynamic behaviour of and the stiffness of asphalt mixtures. In addition, asphalt mixtures containing glass have less temperature sensitivity compared to conventional mixtures [44]. In another study by Jony et al. (2011), the effect of utilizing different fillers (including glass powder) at different rates in asphalt mixtures was investigated. The results of this investigation indicated that using glass powder as filler improves the Marshall Stability of asphalt mixtures in comparison with the asphalt mixtures made with Portland cement or limestone powder as filler [45]. Pereira et al. (2010) conducted research on the utilization of waste flat glass as filler in asphalt mixtures. This research concluded that waste glass can be effectively used as filler in asphalt mixtures. In another field study, two sections of road using two sizes of crushed glass were constructed in Minnesota [46]. Referring to Marti et al. (2002), the results of a rutting test on these roads revealed that the incorporation of waste glass with a size of 9.5 mm in asphalt mixtures provides asphalt mixtures with less dynamic stability compared to asphalt mixtures containing waste glass with a maximum size of 4.75 mm [47]. Other research by Arnold et al. (2008) showed that the addition of up to 30% glass waste by mass of aggregates will not significantly change the aggregates performance [48]. Shafabakhsh and Sajed (2014) concluded that asphalt mixtures containing 10 to 15% crushed glass perform satisfactorily [49]. Finkle and Ksaibati (2007) reported that waste glass can be used as an alternative to the virgin road base materials. However, the glass content of up to 20% and maximum size of 12 mm was recommended based on this research [50]. Wu et al. (2013) investigated the performance of asphalt mixtures containing waste glass as fine aggregate. The maximum size of 4.75 mm and the optimum content of 10% were recommended by this research [34]. In a report published by Australian Road Research Board (ARRB) Group for the Packaging Stewardship Forum (PSF) of the Australian food and grocery council (2012), the glass content of up to 20% was recommended for the utilization in asphalt mixtures as fine aggregate. This report limits the utilization of waste glass to 30% by mass of the total fine aggregate in asphalt mixture [51]. Referring to Su and Chen (2002), in a research program in Taiwan, the engineering properties of the asphalt mixtures incorporating the crushed glass waste were studied through the laboratory and Materials 2018, 11, 1053 4 of 25

field tests. The result of this research revealed that the utilization of glass waste in asphalt mixtures provides substantial economical and engineering advantages [52]. Pioneer Road Services carried out the first glass mix trials in Australia in 2003. The roads were compared with conventional asphalt roads for skid resistance properties. The investigation showed that the skid resistance of the asphalt mixtures containing glass waste is similar to conventional asphalt mixtures [53]. Based on research by Viswanathan (1996), the waste glass can be used in highway construction [54]. In general, glass is typically brittle and has very low impact resistance. This physical property of glass has been used positively in crushing the waste glass in desirable sizes with low energy consumption. Furthermore, glass shows high volumetric stability under high temperatures of up to 700 ◦C. The thermal expansion coefficient and softening point of glass are in the range of 8.8 to 9.2 × 10−6 cm/◦C and 718 to 738 ◦C, respectively. According to available literature, it can be concluded that the application of glass in asphalt mixtures has both advantages and disadvantages, as summarized in Table1, which introduces some limits on the utilization of glass in asphalt mixture as follows:

• The use of recycled glass is recommended to be limited to 20% as the maximum replacement rate in asphalt mixture • In case of glass content of more than 15% of the total mixture, it is required to add 1 to 2% antistripping agent to the asphalt mixture in order to avoid the stripping problems. Hydrated lime is an effective antistripping agent which can be used in asphalt mixtures containing glass. • Suitable particle size of glass as aggregates in asphalt mixture is 4.75 mm or smaller.

Table 1. Advantages and disadvantages of utilization of glass in asphalt mixture.

Advantage Description Since the glass particles have low water absorption, the pavement surface gets Increased road safety dry faster after rain Easier to compact and cartage over Glass asphalt mixtures hold heat longer compared to conventional longer distance asphalt mixtures Glass asphalt surfaces are more reflective in comparison with conventional Improved night time road visibility asphalt surfaces Glass wastes are not disposed into the landfills offering environmental benefits Waste reduction and saving costs The presence of long and flat particles will positively affect the workability of Improved workability asphalt mixtures Commercial benefits Raw materials are replaced by glass resulting in savings on costs of materials No need to change asphalt The same construction method used for conventional asphalt mixtures can be paving process used for asphalt mixtures containing glass Improved resistance to thermal cracking The small inflation coefficient of glass improves the thermal cracking resistance Disadvantage Description Bleeding problem Low bitumen absorption and density may cause a bleeding problem The smooth surface of glass particles reduces the adhesion of asphalt film to the Stripping problem crushed glass, which may cause stripping of the asphalt mixture. The angularity and friction angle of glass particles provides inadequate Decreased transverse stability transverse stability, particularly at braking or start-up The high silica content in glass particles will make asphalt mixtures made with Sensitive to water damage glass have more moisture sensitivity depending on the glass particle size or the glass content in asphalt mixture The presence of long and flat particles (particularly in case of large glass Abrasion of tires particles size) may result in abrasion of tires Decreased skid resistance High amount of large size glass particles cause a decrease in skid resistance Materials 2018, 11, 1053 5 of 25

Through this information, it can be easily understood that the application of waste materials in asphalt mixtures directly affects the behaviour of the asphalt mixtures, leading to both advantages and disadvantages of overall asphalt mixture performance. Recognizing this fact, having knowledge about the properties of individual components in asphalt mixtures and their combination will result in selecting the best combination of aggregates for designing an optimum asphalt mixture.

3. Experimental Work

3.1. Materials In the present study, RCA, glass and basalt have been used as aggregates and the original bitumen studied in this research corresponds to C320, which is the most common binder for wearing courses subjected to heavy loading and/or in hot climates. The typical characteristics of Bitumen C320 are presented in Table2.

Table 2. Characteristics of the original bitumen.

Characteristics Unit Methods Value Softening point ◦C AS 2341.18 [55] 52 Penetration at 25 ◦C dmm AS 2341.12 [56] min 40 Flashpoint ◦C AS 2341.14 [57] min 250 Viscosity at 60 ◦C Pa·s AS 2341.2 [58] 320 Viscosity at 135 ◦C Pa·s AS 2341.2 [58] 0.5 Speciﬁc Gravity Kg/m3 AS 2341.7 [59] 1.03

The virgin aggregate (basalt) was obtained from Nepean Quarries which is a local quarry in Sydney. RCA was obtained from the Revesby Recycling Centre located in Revesby, NSW, Australia. This centre is a transfer station accepting residential and commercial wastes. Based on a statistical study on RCA samples collected over one year, it was observed that there are different construction wastes in RCA, which is mostly (about 64%) composed of sandstone or an agglomerate of sand and cement paste. In addition, a matrix of portland cement concrete will vary between basalt (i.e., Basic Igneous) and granite (i.e., Acidic Igneous) depending on the source of material and the age of the building from which it came makes 17% of RCA. Also, ceramic, glass and brick make about 19% of RCA. The result of the statistical study on RCA is reported in a separate paper. Recycled glass used in this research was clear crushed glass made from recycled glass and passed through 4.75 mm sieve size and was obtained from Schneppa Glass (Burwood, VIC, Australia). The ﬁllers considered in this research are hydrated lime and Portland cement. Using the correct amount of hydrated lime, approximately 2% by weight, in mix designs will improve the durability of mixtures and will minimize the problem of stripping, particularly in asphalt mixtures made with partial glass substitution.

3.2. Laboratory Tests on Coarse Aggregates As presented in the previous sections, in this research project, attempts are made to evaluate the suitability of RCA as part of coarse aggregate in asphalt mixture. Since the basic properties of materials are essential factors in any asphalt mixture design, the fundamental properties of RCA are investigated through conducting different speciﬁcation tests on different coarse aggregates used in this research (i.e., RCA and basalt).

3.3. Laboratory Tests on Fine Aggregates To achieve the goals of this research, the study of properties of recycled glass as part of ﬁne aggregate in combination with basalt has been considered as part of this research work. In light of this, different tests have been conducted on recycled glass and basalt (passed 4.75 mm sieve size). Materials 2018, 11, 1053 6 of 25

3.4. Laboratory Tests on Asphalt Mixtures Containing Recycled Materials

3.4.1. Sample Preparation In this study, the asphalt specimens were made from materials mixed in the Centre for Infrastructure Engineering (CIE) laboratory at Western Sydney University. About 4 kg of materials were used to produce three batches of laboratory asphalt mixtures for a ﬁnished specimen of diameter 100 ± 2 mm and height of 65 ± 5 mm, in accordance with AS2891.2.1 [60] and AS2891.2.2 [61] using an IPC gyratory compactor. For this experimental work, a group of specimens were prepared without recycled materials (0%) as reference to specimens made with 25% and 50% RCA and 0% glass substitution. In addition, in order to assess the effect of glass on the bitumen absorption of asphalt mixtures containing RCA, two groups of specimens were also prepared with 25% and 50% RCA and glass at the rates of 10% and 20%. The glass substitution was made on each sieve from #4 down to #8. Therefore, 66 samples of the following asphalt mixtures were prepared for this study, as indicated in Table3.

Table 3. Bitumen and aggregate mix combination rates.

Specimen Coarse Aggregate (%) Bitumen Fine Aggregate (%) Mix Name Name RCA BasaltContent (%) Glass Basalt B100-4.5 0 100 4.5 0 100 Mix I B100-5 0 100 5 0 100 B100-5.5 0 100 5.5 0 100 B75-5 25 75 5 0 100 Mix II B75-5.5 25 75 5.5 0 100 B75-6 25 75 6 0 100 B50-5 50 50 5 0 100 B50-5.5 50 50 5.5 0 100 Mix III B50-6 50 50 6 0 100 B50-6.5 50 50 6.5 0 100 B75-G10-5 25 75 5 10 90 Mix IV B75-G10-5.5 25 75 5.5 10 90 B75-G10-6 25 75 6 10 90 B75-G20-5 25 75 5 20 80 Mix V B75-G20-5.5 25 75 5.5 20 80 B75-G20-6 25 75 6 20 80 B50-G10-5 50 50 5 10 90 Mix VI B50-G10-5.5 50 50 5.5 10 90 B50-G10-6 50 50 6 10 90 B50-G20-5 50 50 5 20 80 Mix VII B50-G20-5.5 50 50 5.5 20 80 B50-G20-6 50 50 6 20 80

Figure2 illustrates the design gradation curve used for the preparation of mixtures. It should be noted that portland cement and hydrated lime were used in all asphalt mixtures as ﬁller (passing 0.075 mm sieve). Materials 2018, 11, 1053 7 of 25 Materials 2018, 11, x FOR PEER REVIEW 7 of 25

FigureFigure 2. 2.Gradation Gradation curvecurve of of asphalt asphalt mixtures. mixtures. 3.4.2. Evaluation of Volumetric Properties of Asphalt Mixtures 3.4.2. Evaluation of Volumetric Properties of Asphalt Mixtures It is generally recognized that the volumetric composition of mixtures greatly influence their Itperformance. is generally The recognized volumetric that prop theerties volumetric evaluation composition of asphalt mixtures of mixtures is the greatly fundamental inﬂuence of their performance.asphalt mix The design, volumetric determining properties the evaluation performance of asphaltof asphalt mixtures mixture. is the The fundamental asphalt mixture of asphalt mix design,volumetric determining properties including the performance void content, of voids asphalt filled mixture. with binder The (VFB) asphalt and mixturevoids in mineral volumetric propertiesaggregate including (VMA) voidhave content,been recognized voids ﬁlled as impo withrtant binder parameters (VFB) andaffecting voids the in mineraldurability aggregate and (VMA)performance have been of recognizedasphalt pavements as important [62]. The parametersminimum valu affectinges are typically the durability required for and volumetric performance parameters depending on the asphalt mixture type. of asphalt pavements [62]. The minimum values are typically required for volumetric parameters As mentioned previously, all asphalt mixes in this research are dense-graded asphalt (DGA) dependingwith a onnominal the asphalt size of mixture14 (AC14), type. which are prepared in accordance with Test Method RMS T661 As[63] mentioned and RMS T662 previously, [64] (120 all cycles asphalt of mixes compacti in thison) researchwhich are are identical dense-graded to AS2891.2.1 asphalt [60] (DGA) and with a nominalAS2891.2.2 size of[61], 14 respectively. (AC14), which The are requirements prepared infor accordance volumetric withparame Testters Method of this type RMS of T661 mixture [63] and RMSare T662 summarized [64] (120 cyclesin Table of 4. compaction) In addition, whicha summary are identical of the tests to AS2891.2.1carried out to [60 study] and the AS2891.2.2 mixtures [61], respectively.properties The is explained requirements in the forfollowing volumetric sections. parameters of this type of mixture are summarized in Table4. In addition, a summary of the tests carried out to study the mixtures properties is explained in Table 4. the following sections. Volumetric Parameters Requirements for DGA AC14 (AS2150-2005). Parameter Range Typical Values Description Air VoidTable 4. Volumetric 3–6% parameters 5% requirements Mixtures for prepared DGA AC14 in accordance (AS2150-2005). with RMS T662 VMA 13–20% ≥15 Mixtures prepared in accordance with RMS T662 ParameterVFB 65–80% Range Typical - Values Mixtures prepared in Description accordance with RMS T662 Determined in accordance with Test Method Binder AirFilm Void Index - 3–6%≥7.5 μm5% Mixtures prepared in accordance with RMS T662 Austroads AG:PT/T237 or AS 2891.8 Filler-BinderVMA Ratio 0.8–1.2 13–20% - ≥15 MixturesMixtures prepared prepared in inaccordance accordance with with RMS RMS T662 T662 VFB 65–80% - Mixtures prepared in accordance with RMS T662 Bulk Density Test Determined in accordance with Test Method Binder Film Index - ≥7.5 µm Austroads AG:PT/T237 or AS 2891.8 In this research, the bulk density of compacted samples is determined using the presaturation procedureFiller-Binder in accordance Ratio 0.8–1.2with AS/NZS 2891.9.2 - [65].Mixtures This method prepared is in suitable accordance for with dense-graded RMS T662 mixtures with internal air voids that are largely inaccessible to moisture resulting in low Bulkpermeability. Density Test InMaximum this research, Density the Test bulk density of compacted samples is determined using the presaturation procedureIn in this accordance study, the with maximum AS/NZS density 2891.9.2 of [65 a]. loose This methodsample isof suitablemix is fordetermined dense-graded using mixturesthe withmethylated internal air spirits voids displacement that are largely procedure, inaccessible in acco tordance moisture with resultingAS/NZS 2891. in low7.3 [66]. permeability. Based on this 3 test method, firstly, the density of methylated spirit (ρ) was determined as 0.789 t/m . Maximum Density Test

In this study, the maximum density of a loose sample of mix is determined using the methylated spirits displacement procedure, in accordance with AS/NZS 2891.7.3 [66]. Based on this test method, 3 ﬁrstly, the density of methylated spirit (ρm) was determined as 0.789 t/m . Materials 2018, 11, x 1053 FOR PEER REVIEW 88 of of 25

Voids and Volumetric Properties VoidsThe and voids Volumetric and volumetric Properties properties of asphalt mixtures are determined, in this research, in accordanceThe voids with andAS/NZS volumetric 2891.8 [67]. properties of asphalt mixtures are determined, in this research, in accordance with AS/NZS 2891.8 [67]. 3.4.3. Evaluation of Resilient Modulus of Asphalt Mixtures 3.4.3. Evaluation of Resilient Modulus of Asphalt Mixtures The stiffness of asphalt mixtures is a fundamental property and plays an important role in determiningThe stiffness the performance of asphalt mixturesof asphalt is pavement a fundamental under property traffic loading. and plays The anresilient important modulus role inis thedetermining measure of the stiffness performance of asphalt of asphalt mixtures. pavement In addition, under the traffic resilient loading. modulus The resilientof asphalt modulus mixtures is isthe useful measure in determination of stiffness of asphaltof layer mixtures. thickness In throug addition,h estimation the resilient of the modulus relative of strength asphalt mixturescoefficient is anduseful calculation in determination of Structural of layer Number thickness (SN). through estimation of the relative strength coefficient and calculationIn this ofstudy, Structural resilient Number modulus (SN). test was considered for evaluation of the stiffness of some specimensIn this selected study, resilientbased on modulusthe results test of wasa primary considered test to forassess evaluation the effect of of the the stiffness RCA amount of some as wellspecimens as the selectedasphalt mixture based on composition the results ofon aresilien primaryt modulus. test to assess To this the point, effect the of theasphalt RCA mixtures amount wereas well prepared as the asphalt using different mixture compositioncombinations on but resilient with the modulus. same gradation. To this point, Subsequently, the asphalt the mixtures asphalt weremixtures prepared were usingcompacted different with combinations GyroPac at but the with same the level same gradation.of compaction Subsequently, to make thecylindrical asphalt specimensmixtures were of 100 compacted mm in diameter with GyroPac and 65 at mm the samein height. level of compaction to make cylindrical specimens of 100The mm resilient in diameter modulus, and 65 in mm this in research, height. was determined through an indirect tensile strength test inThe accordance resilient modulus, with AS/NZS in this research,2891.13.1 was [68]. determined In this test, through firstly, an indirectthe diameter tensile strengthand height test of in specimensaccordance were with AS/NZSmeasured. 2891.13.1 The specimen [68]. In thiswas test,placed firstly, in the diametertemperature-controlled and height of specimens cabinet at were the temperaturemeasured. The of specimen25 °C to allow was placedthe temperature in the temperature-controlled in the specimen to reach cabinet equilibrium at the temperature prior to ofthe 25 test.◦C Then,to allow the the machine temperature and in Linear the specimen Variable to reachDifferen equilibriumtial Transformers prior to the (LVDT) test. Then, were the calibrated machine and to conductLinear Variable the test. Differential Transformers (LVDT) were calibrated to conduct the test. During the test,test, repeatedrepeated haversinehaversine loading loading is is applied applied to to the the specimen specimen at theat the frequency frequency of 0.1of Hz0.1 Hzconsidering considering 0.1 s0.1 loading s loading and and 0.9 s0.9 rest s rest period period (Figure (Figure3). 3).

FigureFigure 3. LoadLoad and and horizontal horizontal deformation deformation graph in Resilient Modulus Test.

Following the preconditioning, five load pulses were applied with a certain rise time to the Following the preconditioning, ﬁve load pulses were applied with a certain rise time to the peak peak load at a certain pulse repetition period. The recovered horizontal deformation of the load at a certain pulse repetition period. The recovered horizontal deformation of the specimen after specimen after application of each load pulse was recorded. The Poisson’s ratio is considered as 0.4 application of each load pulse was recorded. The Poisson’s ratio is considered as 0.4 in accordance in accordance with AS 2891.13.1 [68]. The resilient modulus in MPa for each specimen for with AS 2891.13.1 [68]. The resilient modulus (Mr) in MPa for each specimen for each load pulse each load pulse during the resilient modulus test were obtained from the following equation: during the resilient modulus test were obtained from the following equation:

Materials 2018, 11, 1053 9 of 25

(µ + 0.27) Mr = P × (1) H × hc where P is peak load (N), µ is Poisson ratio, H is recovered horizontal deformation of the specimen after load pulse (mm), and hc is the height of specimen (mm).

4. Results and Discussion

4.1. Coarse Aggregate Tests Analysis The properties of RCA and basalt were investigated throughout a comprehensive experimental work. The results of these tests on three samples for each aggregate type are summarized in Table5.

Table 5. Test results for evaluation of coarse aggregate properties.

Aggregate Typical Limit Based on Test Test Method RCA Basalt Australian Standards Flakiness Index Test AS 1141.15 [69] 6.9 19.0 25% (max) Particle Shape Test AS 1141.14 [70] 6.2 18.3 35% (max) Water Absorption AS 1141.6.1 [71] 6.30 1.64 2% (max) Particle Density AS 1141.6.1 [71] 2.370 2.640 - Particle Density on Dry Basis AS 1141.6.1 [71] 2.212 2.530 - Particle Density on SSD Basis AS 1141.6.1 [71] 2.351 2.571 - Aggregate Crushing Value AS 1141.21 [72] 29.21 8.91 35% (max) Weak Particles AS 1141.32 [73] 0.23 0.23 1% (max) Wet/Dry Strength Test AS 1141.22 [74] 26.6 8.5 35% (max) Wet Strength AS 1141.22 [74] 119.7 359.2 150 kN (min) Dry Strength AS 1141.22 [74] 163.1 392.9 -

As can be observed in Table5, all properties of RCA, except for water absorption and wet strength, meet the Australian Standards’ requirements, and hence, further investigation on the feasibility of the utilization of RCA as part of basalt in asphalt mixtures appears plausible. Importantly, RCA displays a smaller value for two parameters of Flakiness Index and Particle Shape in comparison with basalt. These two parameters significantly affect the final performance of asphalt mixtures, and better values for these properties can be one of the strong points of RCA contributing to the improvements in compaction, rutting resistance, and workability of asphalt mixtures. In addition, as can be seen in Table5, the results indicate that RCA has substantially higher absorption in comparison to basalt, mainly due to the presence of great amounts of impurities and cracks in RCA. The water absorption of RCA is also more than the typical limit speciﬁed in the Australian Standard. Since the high water absorption of RCA may result in high bitumen absorption of asphalt mixtures, the necessity of ﬁnding and studying potential materials to compensate for this problem of RCA has led to the idea of utilization of glass waste in combination with RCA in asphalt mixture design, which is the main goal of this paper.

4.2. Fine Aggregate Tests Analysis As discussed in the previous sections, the recycled glass is used as part of ﬁne aggregates in this research to compensate for high absorption of RCA. Hence, some of the properties of glass and basalt were studied through conducting a series of tests. These tests and their results analysis are summarized in Table6. The data given in Table4 clearly displays the low amount of water absorption of glass in comparison with ﬁne basalt and Australian standard limits, which makes it an adequate option for combination with RCA. Materials 2018, 11, 1053 10 of 25

Table 6. Test results for evaluation of ﬁne aggregate properties.

Materials 2018, 11, x FOR PEER REVIEW Aggregate Typical Limit Based10 onof 25 Test Test Method Glass Basalt Australian Standards Water AbsorptionTable 6. Test Results AS 1141.5 for Evaluation [75] of 0.10Fine Aggregate 2.35 Properties. 3% (max) Particle Density AS 1141.5 [75] 2.489 2.879 - Aggregate Typical Limit Based on Particle DensityTest on Dry BasisTest AS 1141.5 Method [75] 2.483 2.610 - Particle Density on SSD Basis AS 1141.5 [75]Glass 2.485 Basalt 2.668 Australian - Standards Water Absorption AS 1141.5 [75] 0.10 2.35 3% (max) Particle Density AS 1141.5 [75] 2.489 2.879 - 4.3. Volumetric Analysis of Asphalt Mixtures Containing RCA Particle Density on Dry Basis AS 1141.5 [75] 2.483 2.610 - TheParticle volumetric Density on properties SSD Basis of AS the 1141.5 basalt-RCA [75] asphalt 2.485 mixtures 2.668 were determined - and then compared with the standards specifications. According to Austroads (2014), the essential parameters in the4.3. level Volumetric 1 of mix Analysis design of include Asphalt Mixtures air voids, Containing voids in RCA mineral aggregate (VMA), and voids filled with binder (VFB),The volumetric [76]. properties of the basalt-RCA asphalt mixtures were determined and then Tablecompared7 presents with the the standards properties specifications. obtained for Accord asphalting to mixtures Austroads with (2014), different the essential bitumen parameters content and aggregatein the combinationlevel 1 of mixat design a selected include level air ofvoids, gyrations voids in (120 mineral cycles). aggregate (VMA), and voids filled with binder (VFB), [76]. Table 7 presents theTable properties 7. Volumetric obtained properties for asphalt of asphaltmixtures mixtures. with different bitumen content and aggregate combination at a selected level of gyrations (120 cycles). Specimen AV Water Bulk Density VMA VFB Binder Film Filler-Binder Height Name (%) AbsorptionTable (%) 7. Volumetric(gr/cm3) Properties(%) of Asphalt(%) Mixtures.Index (µm) Ratio (mm) B100-4.5Specimen 7.2AV 0.46Water Bulk 2.398 Density 16.4VMA 59.6VFB Binder 6.9 Film Filler-Binder 1.2 Height 69.0 B100-5Name 5.4(%) Absorption 0.17 (%) 2.439(gr/cm3) 15.4(%) 69.0(%) Index 7.5 (µm) 1.1Ratio (mm) 67.0 B100-5.5B100-4.5 4.17.2 0.11 0.46 2.441 2.398 15.8 16.4 78.659.6 8.7 6.9 1.0 1.2 69.0 66.3 B75-5B100-5 6.75.4 0.43 0.17 2.398 2.439 15.3 15.4 59.769.0 6.4 7.5 1.1 1.1 67.0 69.7 B75-5.5B100-5.5 5.44.1 0.23 0.11 2.410 2.441 15.3 15.8 68.778.6 7.4 8.7 1.0 1.0 66.3 67.6 B75-6B75-5 4.86.7 0.15 0.43 2.411 2.398 15.7 15.3 73.859.7 8.2 6.4 0.9 1.1 69.7 67.0 B50-5B75-5.5 7.35.4 0.56 0.23 2.355 2.410 15.3 15.3 55.368.7 5.9 7.4 1.1 1.0 67.6 73.6 B50-5.5B75-6 6.04.8 0.31 0.15 2.371 2.411 15.1 15.7 64.073.8 6.8 8.2 1.0 0.9 67.0 71.0 B50-6B50-5 5.47.3 0.24 0.56 2.373 2.355 15.5 15.3 69.155.3 7.5 5.9 0.9 1.1 73.6 68.9 B50-6.5B50-5.5 4.56.0 0.16 0.31 2.359 2.371 16.5 15.1 77.164.0 9.0 6.8 0.9 1.0 71.0 68.2 B50-6 5.4 0.24 2.373 15.5 69.1 7.5 0.9 68.9 B50-6.5 4.5 0.16 2.359 16.5 77.1 9.0 0.9 68.2 4.3.1. Optimum Bitumen Content Determination 4.3.1. Optimum Bitumen Content Determination To determine the optimum bitumen content for the asphalt mixture, the procedure indicated by AustralianTo determine standards, the optimum AGPT04B-14, bitumen was content followed for the in asphalt this research. mixture, the Three procedure specimens indicated at each bitumenby Australian content (4.5%,standards, 5%, AGPT04B-14, 5.5%, 6%, and was 6.5%) follow wereed in tested this research. for maximum Three specimens density, bulkat each density, bitumen content (4.5%, 5%, 5.5%, 6%, and 6.5%) were tested for maximum density, bulk density, and subsequently air voids and VMA calculations. The results of these tests and calculations are used and subsequently air voids and VMA calculations. The results of these tests and calculations are to determineused to determine the optimum the optimum bitumen bitumen content content that providesthat provides air voidsair voids within within the the specified specified limitslimits and VMAand near VMA to the near minimum to the minimum value. Accordingvalue. According to the to results the results obtained, obtained, Figure Figure4 illustrates 4 illustrates the effectthe of bitumeneffect content of bitumen and content RCA content and RCA on content air voids on air of asphaltvoids of mixtures.asphalt mixtures.

FigureFigure 4. Effect 4. Effect of bitumen of bitumen content content and RCAand RCA content content on air on voids air voids of Mix of IMix containing I containing virgin virgin aggregate aggregate and Mix II and Mix III containing RCA as coarse aggregate. and Mix II and Mix III containing RCA as coarse aggregate.

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The airair voidvoid contentcontent in in the the mix mix is ais function a function of bitumen of bitumen content, content, degree degree of compaction of compaction and VMA. and TheVMA. air The void air percentage void percentage in the mixture in the mixture affects mix affect stiffness,s mix stiffness, fatigue resistance, fatigue re andsistance, durability. and durability. As shown inAs thisshown figure, in this air voidsfigure, decrease air voids with decrease the bitumen with the content bitumen increase. content Air increase. voids of Air mixtures voids of made mixtures with RCAmade are with substantially RCA are substantially higher than thehigher control than mixtures the control because mixtures of porous because cement of porous paste attached cement topaste the virginattached aggregates to the virgin and aggregates also porous and structure also poro of someus structure aggregates of some in the aggregates RCA. in the RCA. Generally, asphaltasphalt mixtures mixtures should should have have the the lowest lowe practicalst practical air voids air voids in order in order to reduce to reduce the binder the ageingbinder andageing the and permeability the permeability and subsequent and subseque strippingnt stripping problems. problems. However, However, referring to referring Austroads to (2014),Austroads plastic (2014), flow andplastic subsequent flow and bleeding, subsequent flushing, bleeding, shoving flushing, or permanent shoving deformation or permanent of the pavementdeformation may of occur the ifpavement the air voids may are occur too low if (lessthe air than voids about are 2%). too Accordingly, low (less asthan can beabout observed 2%). inAccordingly, Figure4, some as can of thebe observed mixtures in (i.e., Figure B100-4.5, 4, some B75-5 of andthe mixtures B50-5) cannot (i.e., B100-4.5, be acceptable B75-5 in and terms B50-5) of aircannot voids be requirements. acceptable in As terms discussed of air previously,voids requirements. the optimum As bitumendiscussed content previously, can be the obtained optimum for designbitumen air content voids ofcan 5%. be Based obtained on the fo results,r design the air optimum voids of bitumen 5%. Based content on the was results, found tothe be optimum 5.1% for referencebitumen content samples was (0% found RCA), to 5.8% be for5.1% samples for reference with 25% samples RCA and(0% 6.2%RCA), for 5.8% samples for samples with 50% with RCA, 25% as illustratedRCA and 6.2% in Figure for samples4. with 50% RCA, as illustrated in Figure 4. Furthermore, VMA is another important volumetric property which should be checked for selection ofof thethe finalfinal bitumen bitumen content. content. VMA VMA is is the the combination combination of airof air voids voids in thein compactedthe compacted mix mix and theand volumethe volume occupied occupied by the by effectivethe effective binder binder which which is total is total binder binder minus minus any binderany binder absorbed absorbed into theinto aggregate. the aggregate. VMA VMA is a functionis a function of the of gradationthe gradation and and the particlethe particle shape shape and and surface surface texture texture of the of aggregatethe aggregate particles. particles. VMA VMA should should be largebe large enough enough to provide to provide a sufficient a sufficient amount amount of air of voidsair voids in the in compactedthe compacted mixture mixture for ensuring for ensuring the asphalt the asphalt mixture mi stabilityxture stability while leaving while enough leaving space enough for thespace binder for tothe ensure binder the to mixtureensure the durability. mixture If durability. VMA is too If low,VMA the is bindertoo low, would the binder be insufficient would be for insufficient cohesion and for durabilitycohesion and whereas durability too high whereas VMA too results high in VMA more re costlysults asphaltin more mixtures costly asphalt due to increasedmixtures due binder to volumeincreased to binder satisfy volume the air voids to satisfy requirements. the air voids requirements. The variation of VMAVMA withwith bitumenbitumen contentcontent forfor MixMix I,I, Mix Mix II II and and Mix Mix III III are are shown shown in in Figure Figure5. As5. As can can be be observed observed in Figurein Figure5, VMA 5, VMA increases increase withs with bitumen bitumen content content after after a minimum a minimum point. point. The testThe resultstest results on different on different samples samples showed showed that VMA that ofVMA mixtures of mixtures containing containing RCA is RCA quite is a bitquite lower a bit than lower the controlthan the samples control whichsamples can which be as can a result be as of a higherresult of bitumen higher absorptionbitumen absorpti of RCAon resulting of RCA inresulting the lower in amountthe lower of amount not-absorbed of not-absorbed binder (effective binder binder).(effective As binder). illustrated As illustrated in Figure5 in, mixtures Figure 5, at mixtures optimum at bitumenoptimum content bitumen meet content the requirements meet the requirements of 15% (minimum) of 15% (minimum) for VMA. for VMA.

Figure 5. Effect ofof bitumenbitumen content content and and RCA RCA content content on on VMA VMA of Mixof Mix I containing I containing virgin virgin aggregate aggregate and Mixand Mix II and II Mixand Mix III containing III containi RCAng RCA as coarse as coarse aggregate. aggregate.

4.3.2. Determination of Bulk Density and Water AbsorptionAbsorption Bulk density is an important parameter used for volumetric properties evaluation of asphalt Bulk density is an important parameter used for volumetric properties evaluation of asphalt mixtures. Bulk density of Mix I, Mix II and Mix III are shown in Figure 6. It can be seen that bulk mixtures. Bulk density of Mix I, Mix II and Mix III are shown in Figure6. It can be seen that bulk densities of mixtures containing RCA are considerably lower than bulk density of mixtures made densities of mixtures containing RCA are considerably lower than bulk density of mixtures made with with virgin aggregates (Mix I), mainly because of the low density of cement paste and RCA virgin aggregates (Mix I), mainly because of the low density of cement paste and RCA particles. particles.

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Figure 6. Effect of bitumen content and RCA content on bulk density of Mix I containing virgin Figure 6. EffectEffect of of bitumen bitumen content content and and RCA RCA content content on on bulk bulk density density of of Mix I containing virgin aggregate and Mix II and Mix III containing RCA as coarse aggregate. aggregate and Mix II and Mix III cont containingaining RCA as coarse aggregate. Furthermore, the experimental results show the water absorption increase of the mixtures by Furthermore, the experimentalexperimental resultsresults show show the the water water absorption absorption increase increase of theof the mixtures mixtures by theby the increase in amount of RCA at the same bitumen content due to porous structure of RCA, as theincrease increase in amount in amount of RCA of RCA at the at same the bitumensame bitu contentmen content due to porousdue to structureporous structure of RCA, asof expectedRCA, as expected and shown in Figure 7. expectedand shown and in shown Figure 7in. Figure 7.

Figure 7. Effect of bitumen content and RCA content on water absorption of Mix I containing virgin Figure 7. Effect of bitumen content and RCA content on water absorption of Mix I containing virgin Figureaggregate 7. Effect and Mix of bitumen II and Mix content III cont andaining RCA RCA content as coarse on water aggregate. absorption of Mix I containing virgin aggregate and Mix II and Mix III cont containingaining RCA as coarse aggregate. 4.3.3. Determination of Voids Filled with Bitumen (VFB) 4.3.3. Determination of Voids Filled with Bitumen (VFB) 4.3.3.Another Determination important of Voids volumetric Filled withparameter Bitumen is (VFB)voids filled with binder (VFB). VFB is defined as Another important volumetric parameter is voids filled with binder (VFB). VFB is defined as the ratioAnother of the important effective binder volumetric (by volume) parameter and is the voids VMA. ﬁlled Mixtures with binder with low (VFB). VFB VFB are isdry deﬁned and lack as the ratio of the effective binder (by volume) and the VMA. Mixtures with low VFB are dry and lack thedurability, ratio of cohesion the effective and binderfatigue (by resistance. volume) and the VMA. Mixtures with low VFB are dry and lack durability, cohesion and fatigue resistance. durability,These cohesionmixtures andmay fatigue also be resistance. more permeable, whereas asphalt mixtures with too high VFB can These mixtures may also be more permeable, whereas asphalt mixtures with too high VFB can becomeThese unstable mixtures and may susceptible also be moreto rutting. permeable, Figure whereas 8 illustrates asphalt the mixturesvariation withof VFB too with high the VFB RCA can become unstable and susceptible to rutting. Figure 8 illustrates the variation of VFB with the RCA becomeand bitumen unstable content. and susceptible The VFB values to rutting. obtained Figure for8 illustrates asphalt mixtures the variation containing of VFB RCA with theare RCArelatively and and bitumen content. The VFB values obtained for asphalt mixtures containing RCA are relatively bitumenlower compared content. Theto the VFB control values samples obtained because for asphalt of higher mixtures absorption containing of RCA RCA are leading relatively to lowera less lower compared to the control samples because of higher absorption of RCA leading to a less comparedamount of tonot-absorbed the control binder samples (effective because binder). of higher absorption of RCA leading to a less amount of amount of not-absorbed binder (effective binder). not-absorbed binder (effective binder).

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Figure 8. Effect of bitumen content and RCA content on VFB of Mix I containing virgin aggregate Figure 8. Effect of bitumen content and RCA content on VFB of Mix I containing virgin aggregate and and Mix II and Mix III containing RCA as coarse aggregate. Mix IIFigure and Mix8. Effect III containing of bitumen RCA content as coarseand RCA aggregate. content on VFB of Mix I containing virgin aggregate and Mix II and Mix III containing RCA as coarse aggregate. 4.3.4. Determination of Binder Film Index (BFI) 4.3.4. Determination of Binder Film Index (BFI) 4.3.4.Binder Determination Film Index of Binder(BFI) is Film another Index parameter (BFI) that can be considered at the volumetric design BinderstageBinder as Film a guide Film Index toIndex the (BFI) incorporation(BFI) is another is another parameterof sufficientparameter that binder th canat can in be thebe considered consideredasphalt mixture at at the the volumetric to volumetric ensure adequate design design stage as a guidedurability,stage as to a the guide cohesion, incorporation to the resistance incorporation of sufficient to the of effects sufficient binder of moisture in binder the asphalt in and the fatigue asphalt mixture resi mixture tostance ensure to(Austroads, ensure adequate adequate 2014). durability, cohesion,BFIdurability, is resistance a function cohesion, to of the theresistance effects surface of toarea moisture the ofeffects filler and ofan fatiguemoistured the aggregates resistance and fatigue as (Austroads, well resi stanceas the 2014). (Austroads,effective BFI bitumen is 2014). a function content. According to the results obtained, the binder film index of Mix I, Mix II and Mix III are of theBFI surface is a function area of of filler the andsurface the area aggregates of filler asan welld the as aggregates the effective as well bitumen as the content.effective Accordingbitumen to shown in Figure 9. As can be observed in Figure 9, BFI values for Mix II and Mix III are lower than the resultscontent. obtained, According the to binder the results film indexobtained, of Mix the I,bi Mixnder IIfilm and index Mix IIIof areMix shownI, Mix II in and Figure Mix9 .III As are can be BFIshown for incontrol Figure samples 9. As can (Mix be observedI) at the insame Figure bitumen 9, BFI content,values for as Mixmore II andbinder Mix is III absorbed are lower by than the observed in Figure9, BFI values for Mix II and Mix III are lower than BFI for control samples (Mix I) at mixturesBFI for control incorporating samples RCA,(Mix resultingI) at the samein less bitumen aggregate content, particles as morecoating binder due tois absorbedthe reduction by the of the sameavailablemixtures bitumen incorporatingbinder content, for this asRCA, purpose. more resulting binder As can in is absorbedlessbe expeaggregatected, by the theparticles mixturesBFI is coatingincreased incorporating due with to the the RCA,reduction increase resulting inof in less aggregatebitumenavailable content. binder particles for coatingthis purpose. due toAs the can reduction be expected, of available the BFI is binder increased for thiswith purpose.the increase As in can be expected,bitumen the content. BFI is increased with the increase in bitumen content.

Figure 9. Effect of bitumen content and RCA content on BFI of Mix I containing virgin aggregate and Mix II and Mix III containing RCA as coarse aggregate. FigureFigure 9. Effect 9. Effect of bitumen of bitumen content content and and RCA RCA contentcontent on on BFI BFI of of Mix Mix I containing I containing virgin virgin aggregate aggregate and and Mix II and Mix III containing RCA as coarse aggregate. Mix IIIn and addition, Mix III as containing can be seen RCA in asFigure coarse 9, aggregate.all samples at their optimum bitumen content meet the minimumIn addition, requirements as can beof 7.5seen µm in forFigure BFI. 9, all samples at their optimum bitumen content meet the Inminimum addition, requirements as can be seenof 7.5 inµm Figure for BFI.9, all samples at their optimum bitumen content meet the minimum4.4. Volumetric requirements Analysis of of 7.5 Asphalµmt for Mixtures BFI. Containing RCA and Glass 4.4. VolumetricSince asphalt Analysis mixtures of Asphal madet Mixtures with RCA Containing have the RCA problem and Glass of high absorption, as discussed in 4.4. VolumetricpreviousSince sections, asphalt Analysis mixturesit ofis Asphaltdesired made Mixturesto optimizewith RCA Containing the have absorption the RCA problem andcharacteristics Glassof high absorption, of these asphalt as discussed mixtures in Sincebyprevious adding asphalt sections, recycled mixtures it glass, is desired which made to is with optimizethe primary RCA the have objective absorption the problem of thischaracteristics research of high work. of absorption, these asphalt as mixtures discussed in previous by adding sections, recycled it is desiredglass, which to optimize is the primary the absorption objective of characteristics this research work. of these asphalt mixtures by adding recycled glass, which is the primary objective of this research work. Materials 2018, 11, 1053 14 of 25

MaterialsTo this 2018 end,, 11 different, x FOR PEER asphalt REVIEW mixtures containing RCA with three glass contents of 0%,14 of 10% 25 and 20% (by weight of ﬁne aggregates) were prepared for evaluating the effect of the addition of glass to RCA-basaltTo asphaltthis end, mixtures. different asphalt For this mixtures purpose, contai differentning RCA combinations with three of glass aggregates contents atof different0%, 10% rates of bitumenand 20% content (by weight of 5%, of 5.5%fine aggregates) and 6% were were considered prepared tofor makeevaluating specimens the effect with of 100the mmaddition diameter of at glass to RCA-basalt asphalt mixtures. For this purpose, different combinations of aggregates at a required level of gyration (120 cycles) for the considered trafﬁc category. Table8 presents the results different rates of bitumen content of 5%, 5.5% and 6% were considered to make specimens with 100 of volumetric analysis for asphalt mixtures containing RCA and glass with different bitumen content. mm diameter at a required level of gyration (120 cycles) for the considered traffic category. Table 8 presents the results of volumetric analysis for asphalt mixtures containing RCA and glass with Table 8. Volumetric properties of asphalt mixtures containing RCA and glass. different bitumen content.

Specimen AVTable 8. VolumetricWater PropertiesBulk Density of AsphaltVMA MixturesVFB ContainingBinder RCA Film and Glass.Filler-Binder Height Name (%) Absorption (%) (gr/cm3) (%) (%) Index (µm) Ratio (mm) B75-G10-5Specimen 5.9AV 0.29Water Bulk 2.394 Density VMA 14.8 VFB 63.9 Binder 6.6 Film Filler-Binder 1.1 Height 68.2 Name (%) Absorption (%) (gr/cm3) (%) (%) Index (µm) Ratio (mm) B75-G10-5.5 4.7 0.16 2.400 15.1 73.0 7.7 1.0 67.1 B75-G10-6B75-G10-5 4.35.9 0.14 0.29 2.4062.394 14.8 15.3 63.9 76.3 8.26.6 1.1 0.9 68.2 66.1 B75-G20-5B75-G10-5.5 5.64.7 0.27 0.16 2.3842.400 15.1 14.5 73.065.2 6.67.7 1.0 1.1 67.1 68.1 B75-G10-6 4.3 0.14 2.406 15.3 76.3 8.2 0.9 66.1 B75-G20-5.5 4.6 0.15 2.394 14.6 72.7 7.4 1.0 67.8 B75-G20-5 5.6 0.27 2.384 14.5 65.2 6.6 1.1 68.1 B75-G20-6 4.2 0.12 2.398 14.9 76.3 7.9 0.9 65.7 B75-G20-5.5 4.6 0.15 2.394 14.6 72.7 7.4 1.0 67.8 B50-G10-5 6.9 0.54 2.352 14.9 56.9 5.9 1.1 69.9 B75-G20-6 4.2 0.12 2.398 14.9 76.3 7.9 0.9 65.7 B50-G10-5.5 5.5 0.27 2.363 14.9 67.0 7.0 1.0 69.7 B50-G10-5 6.9 0.54 2.352 14.9 56.9 5.9 1.1 69.9 B50-G10-6 4.9 0.18 2.366 15.3 72.1 7.7 0.9 69.0 B50-G10-5.5 5.5 0.27 2.363 14.9 67.0 7.0 1.0 69.7 B50-G20-5 6.5 0.30 2.339 14.7 59.2 6.0 1.1 69.4 B50-G10-6 4.9 0.18 2.366 15.3 72.1 7.7 0.9 69.0 B50-G20-5.5 5.3 0.21 2.353 14.6 67.7 6.9 1.0 68.6 B50-G20-5 6.5 0.30 2.339 14.7 59.2 6.0 1.1 69.4 B50-G20-6 4.2 0.14 2.364 14.7 75.8 7.7 0.9 67.7 B50-G20-5.5 5.3 0.21 2.353 14.6 67.7 6.9 1.0 68.6 B50-G20-6 4.2 0.14 2.364 14.7 75.8 7.7 0.9 67.7 4.4.1. Determination of optimum bitumen content for asphalt mixtures with glass 4.4.1. Determination of optimum bitumen content for asphalt mixtures with glass Similar to the procedure explained in Section 4.3.1, the optimum bitumen content for the asphalt Similar to the procedure explained in Section 4.3.1, the optimum bitumen content for the mixturesasphalt made mixtures with RCAmade and with glass RCA were and determined glass were in determined accordance in with accordance Australian with standards. Australian To this end andstandards. in order To tothis compare end and thein order effect to of compare glass addition the effect to of RCA-basaltglass addition mixtures, to RCA-basalt three mixtures, specimens at differentthree bitumen specimens contents at different of 5%, bitumen 5.5% and contents 6% made of 5%, with 5.5% 25% and RCA 6% and made recycled with glass25% atRCA rates and of 10% and 20%recycled were glass prepared at rates and of tested 10% and for maximum20% were density,prepared bulk and density,tested for and maximum subsequently density, air voidsbulk and VMAdensity, calculations. and subsequently air voids and VMA calculations. TheThe same same bitumen bitumen content content and and glass glass contentcontent was was also also considered considered for forpreparation preparation of samples of samples containingcontaining 50% 50% RCA. RCA. The effect of bitumen content and glass content on air voids of asphalt mixtures is illustrated in The effect of bitumen content and glass content on air voids of asphalt mixtures is illustrated in Figures 10 and 11. As can be clearly observed in Figures 10 and 11, air voids of mixtures containing Figures 10 and 11. As can be clearly observed in Figures 10 and 11, air voids of mixtures containing glass are lower than the mixtures containing RCA without glass due to highly hydrophobic glassproperty are lower of thanglass. the In mixtures addition, containing air voids decrease RCA without with the glass increase due to of highly bitumen hydrophobic content inproperty all of glass.samples. In addition, air voids decrease with the increase of bitumen content in all samples.

FigureFigure 10. Effect 10. Effect of bitumen of bitumen content content and and glass glass content content on airon voidsair voids of Mix of Mix II containing II containing 25% 25% RCA RCA without without glass and Mix IV and Mix V containing 25% RCA as coarse aggregate and glass as fine glass and Mix IV and Mix V containing 25% RCA as coarse aggregate and glass as fine aggregate. aggregate.

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FigureFigureFigure 11. 11.Effect 11. Effect Effect of bitumenof of bitumen bitumen content content content and and and glass glassglass content contentcontent on airon voids airair voidsvoids of Mix of of Mix IIIMix containing III III containing containing 50% 50% RCA50% RCA withoutRCA without glass and Mix VI and Mix VII containing 50% RCA as coarse aggregate and glass as fine glasswithout and Mix glass VI and and Mix Mix VI VII and containing Mix VII 50% containing RCA as 50% coarse RCA aggregate as coarse and aggregate glass as fineand aggregate.glass as fine aggregate.aggregate.

Importantly,Importantly,Importantly, the the resultsthe results results of volumetricof of volumetric volumetric analysis analysisanalysis and and air voidairair voidvoid calculations calculationscalculations based based based on on the on the bulk the bulk densitybulk testdensity anddensity maximum test test and and densitymaximum maximum test density revealdensity that testtest therevealreveal optimum that the bitumen optimumoptimum content bitumenbitumen of asphalt content content mixturesof of asphalt asphalt varies mixtures varies with the amount of waste glass used, so that mixtures containing more glass require withmixtures the amount varies ofwith waste the amount glass used, of waste so that glass mixtures used, so containingthat mixtures more containing glass require more glass less require bitumen, less bitumen, as presented in Figures 10 and 11. The results of the obtained optimum bitumen asless presented bitumen, in Figuresas presented 10 and in 11 Figures. The results 10 and of 11. the The obtained results optimum of the obtained bitumen optimum content based bitumen on all content based on all specimens studied in this research work are presented in Figure 12. specimenscontent based studied on inall thisspecimens research studied work in are this presented research inwork Figure are 12presented. in Figure 12.

Figure 12. Optimum bitumen content (OBC) of asphalt mixtures. Figure 12. Optimum bitumen content (OBC) of asphalt mixtures. Furthermore,Figure as discussed 12. Optimum previously, bitumen VMA content is another (OBC) parameter of asphalt required mixtures. to be considered in selecting the optimum bitumen content. The variation of VMA with bitumen content for mixtures Furthermore, as discussed previously, VMA is another parameter required to be considered in Furthermore,containing 25% as and discussed 50% RCA previously, made with VMArecycled is glass another or without parameter glass required are illustrated to be in considered Figures in selecting13 and the14, respectively.optimum bitumen content. The variation of VMA with bitumen content for mixtures selecting the optimum bitumen content. The variation of VMA with bitumen content for mixtures containingThe 25%test resultsand 50% on differentRCA made samples with showedrecycled that glass VMA or withoutof mixtures glass containing are illustrated glass is in quite Figures a containing 25% and 50% RCA made with recycled glass or without glass are illustrated in Figures 13 13 bitand lower 14, respectively. than the samples made with RCA without glass. It can be due to the lower air voids and and 14lower,The respectively. testparticle results density on different of combined samples mineral showed aggregates that VMA in samplesof mixtures made containing with RCA glass and is glass. quite a bitThe However,lower test than results in theall group onsamples different of Mixes, made samples VMAwith RCAincreases showed without with that bitumengl VMAass. It of contentcan mixtures be dueafter containing to a minimumthe lower glass point.air voids is quite and a bit lowerlower than particle the samples density made of combined with RCA mineral without aggregates glass. It can in besamples due to made the lower with air RCA voids and and glass. lower particleHowever, density in all of group combined of Mixes, mineral VMA aggregates increases in with samples bitumen made content with af RCAter a and minimum glass. However,point. in all group of Mixes, VMA increases with bitumen content after a minimum point.

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Figure 13. Effect of bitumen content and glass content on VMA of Mix II containing 25% RCA withoutFigure 13.13. glass EffectEffect and of of bitumenMix bitumen IV and content content Mix andV andcontaining glass glass content content 25% on RCA VMA on VMAas of coarse Mix of II Mix containingaggregate II containing 25%and RCAglass 25% withoutas RCA fine aggregate.glasswithout and glass Mix IVand and Mix Mix IV V and containing Mix V 25%containing RCA as 25% coarse RCA aggregate as coarse and aggregate glass asﬁne and aggregate. glass as fine aggregate.

Figure 14.14. EffectEffect of of bitumen bitumen content content and and glass glass content conten ont VMA on VMA of Mix of III Mix containing III containing 50% RCA 50% without RCA Figure 14. Effect of bitumen content and glass content on VMA of Mix III containing 50% RCA withoutglass and glass Mix VIand and Mix Mix VI VIIand containing Mix VII containing 50% RCA as50% coarse RCA aggregate as coarse and aggregate glass as and ﬁne aggregate.glass as fine aggregate.without glass and Mix VI and Mix VII containing 50% RCA as coarse aggregate and glass as fine aggregate. As illustrated in Figures 13 and 14, mixtures without glass and containing 10% glass meet the As illustrated in Figures 13 and 14, mixtures without glass and containing 10% glass meet the requirements of 15% (minimum) for VMA at their optimum bitumen content. However, VMA for requirementsAs illustrated of 15% in (minimum)Figures 13 and for 14,VMA mixtures at their without optimum glass bitumen and containing content. However, 10% glass VMAmeet thefor other mixtures containing 20% glass is still in the acceptable range. otherrequirements mixtures of containing 15% (minimum) 20% glass for is VMA still in at the their acceptable optimum range. bitumen content. However, VMA for other mixtures containing 20% glass is still in the acceptable range. 4.4.2. Determination of Bulk Density and Water Absorption for Asphalt Mixtures with Glass 4.4.2. Determination of Bulk Density and Water Absorption for Asphalt Mixtures with Glass 4.4.2.Bulk Determination density test of was Bulk conducted Density and on Water specimens Absorption containing for Asphalt glass and Mixtures RCA to with measure Glass the bulk Bulk density test was conducted on specimens containing glass and RCA to measure the bulk density and water absorption of samples. densityBulk and density water testabsorption was conducted of samples. on specimens containing glass and RCA to measure the bulk Based on the results obtained from the bulk density test on two groups of asphalt mixtures with densityBased and on water the absorptionresults obtained of samples. from the bulk density test on two groups of asphalt mixtures 25% and 50% RCA in combination with different rates of recycled glass, it can be noticed that the with Based25% and on 50%the resultsRCA in obtained combination from with the differentbulk densi ratesty test of recycledon two groupsglass, it ofcan asphalt be noticed mixtures that bulk density decreases with the increase in the glass content due to lower bulk density of glass in thewith bulk 25% density and 50% decreases RCA in withcombination the increase with in different the glass rates content of recycled due to lowerglass, itbulk can density be noticed of glass that comparison with basalt, as illustrated in Figures 15 and 16. inthe comparison bulk density with decreases basalt, aswith illustrated the increase in Figures in the 15 glass and content 16. due to lower bulk density of glass in comparisonIn addition, with the basalt, data obtained as illustrated from thein Figures bulk density 15 and test 16. indicate that water absorption decreases with respect to the amount of recycled glass, and asphalt mixtures containing glass appear to have low water absorption because of the hydrophobic property of glass. Figure 17 illustrates the water absorption of all different specimens.

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Materials 2018,, 11,, 1053x FOR PEER REVIEW 1717 of of 25 Materials 2018, 11, x FOR PEER REVIEW 17 of 25

Figure 15. Effect of bitumen content and glass content on bulk density of Mix II containing 25% RCA without glass and Mix IV and Mix V containing 25% RCA as coarse aggregate and glass as fine aggregate.

Figure 15. Effect of bitumen content and glass content on bulk density of Mix II containing 25% RCA Figurewithout 15. glass EffectEffect and of Mixbitumen bitumen IV and content Mix and V containing glass content 25% on RCA bulk asdensity coarse of aggregate Mix II containing and glass 25% as RCA fine withoutaggregate. glassglass and and Mix Mix IV IV and and Mix Mix V containing V containing 25% RCA25% asRCA coarse as aggregatecoarse aggregate and glass and as fine glass aggregate. as fine aggregate.

Figure 16. Effect of bitumen content and glass content on bulk density of Mix III containing 50% RCA without glass and Mix VI and Mix VII containing 50% RCA as coarse aggregate and glass as fine aggregate.

In addition, the data obtained from the bulk density test indicate that water absorption decreases with respect to the amount of recycled glass, and asphalt mixtures containing glass appearFigure to have 16. Effect low of water bitumen absorption content and because glass content of the on bulk hydrophobic density of Mix property III containing of glass. 50% Figure RCA 17 Figure 16. Effect of bitumen content and glass content on bulk density of Mix III containing 50% RCA illustrateswithout the glassglass water and and Mixabsorption Mix VI VI and and Mix of Mix VIIall differentcontainingVII containing specimens. 50% RCA50% asRCA coarse as aggregatecoarse aggregate and glass and as fine glass aggregate. as fine aggregate.without glass and Mix VI and Mix VII containing 50% RCA as coarse aggregate and glass as fine aggregate. In addition, the data obtained from the bulk density test indicate that water absorption decreasesIn addition, with respect the data to theobtained amount from of recycledthe bulk glass,density and test asphalt indicate mixtures that watercontaining absorption glass decreasesappear to withhave respectlow water to theabsorption amount becauseof recycled of theglass, hydrophobic and asphalt property mixtures of containingglass. Figure glass 17 illustratesappear to thehave water low absorption water absorption of all different because specimens. of the hydrophobic property of glass. Figure 17 illustrates the water absorption of all different specimens.

FigureFigure 17. ComparisonComparison of of water water absorption absorption in asphal asphaltt mixtures with different aggregate type.

Figure 17. Comparison of water absorption in asphalt mixtures with different aggregate type. Figure 17. Comparison of water absorption in asphalt mixtures with different aggregate type.

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Materials 2018, 11, x FOR PEER REVIEW 18 of 25 Materials 2018, 11, x FOR PEER REVIEW 18 of 25 4.4.3. Determination of Voids Filled with Bitumen (VFB) for Asphalt Mixtures with Glass 4.4.3. Determination of Voids Filled with Bitumen (VFB) for Asphalt Mixtures with Glass 4.4.3.Figures Determination 18 and 19 ofillustrate Voids Filled the with variation Bitumen of VFB(VFB) with for Asphalt the bitumen Mixtures content with Glass and glass content. Figures 18 and 19 illustrate the variation of VFB with the bitumen content and glass content. As previouslyAs previouslyFigures stated, 18 stated,and VFB 19 isVFBillustrate one is of one thethe of indicatorsvariation the indicato of of VF asphaltrsB ofwith asphalt mixturethe bitumen mixture performance content performance and in termsglass in termscontent. of durability, of fatigueAsdurability, resistancepreviously fatigue andstated, resistance susceptibility VFB is and one susceptibility toof rutting.the indicato to rutting.rs of asphalt mixture performance in terms of durability, fatigue resistance and susceptibility to rutting.

FigureFigure 18. Effect 18. Effect of bitumenof bitumen content content and and glass glass contentcontent on on VFB VFB of of Mix Mix II containing II containing 25% 25% RCA RCA without without Figureglass and 18. MixEffect IV of and bitumen Mix V contentcontaining and 25% glass RCA content as coarse on VFB aggregate of Mix II and containing glass as 25%fine aggregate.RCA without glassglass and and Mix Mix IV andIV and Mix Mix V V containing containing 25% 25% RCARCA as coarse coarse aggregate aggregate and and glass glass as fine asﬁne aggregate. aggregate.

Figure 19. Effect of bitumen content and glass content on VFB of Mix III containing 50% RCA FigureFigurewithout 19. Effect19. glass Effect of and bitumen of Mix bitumen VI content and content Mix and VII and glasscontaining glass content content 50% on RCA VFBon VFBas of coarse Mixof Mix III aggregate containingIII containing and 50% glass 50% RCA as RCA fine without without glass and Mix VI and Mix VII containing 50% RCA as coarse aggregate and glass as fine glassaggregate. and Mix VI and Mix VII containing 50% RCA as coarse aggregate and glass as fine aggregate. aggregate. As can be observed in Figures 18 and 19, the values obtained for asphalt mixtures made with Asglass canAs and can be RCA observedbe observedare higher in in Figures than Figures the 18 samples18 and and 1919, contai, the ningva valueslues RCA obtained obtained without for glass for asphalt asphalt due mixturesto a mixtures lower made degree made with of with glassglassabsorption and and RCA RCA resulting are are higher higher in increased than than the the effective samples samples binder. containingcontai ning RCA RCA without without glass glass due due to a tolower a lower degree degree of of absorptionabsorption resulting resulting in increasedin increased effective effectivebinder. binder. 4.4.4. Determination of Binder Film Index (BFI) for Asphalt Mixtures with Glass 4.4.4. Determination of Binder Film Index (BFI) for Asphalt Mixtures with Glass 4.4.4. DeterminationAs discussed of previously, Binder Film BFI Index is an (BFI)indicator for Asphaltof adequate Mixtures cohesion with and Glass the incorporation of As discussed previously, BFI is an indicator of adequate cohesion and the incorporation of Assufficient discussed binder previously, in the asphalt BFI mixture. is an indicator of adequate cohesion and the incorporation of sufficient binder in the asphalt mixture. sufficientAccording binder in to the the asphalt results mixture.obtained, the binder film index of different mixtures were investigated in thisAccording research toand the the results variation obtained, of BFI the with binder glass film and index bitumen of different content mixtures in two groups were investigated of samples According to the results obtained, the binder film index of different mixtures were investigated incontaining this research 25% and 50%the variation RCA are ofillustrated BFI with in gl Figuresass and 20 bitumen and 21. content in two groups of samples in thiscontaining research 25% and and the 50% variation RCA are of illustrated BFI with in glass Figures and 20 bitumenand 21. content in two groups of samples containing 25% and 50% RCA are illustrated in Figures 20 and 21.

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FigureFigure 20. Effect 20. Effect of bitumen of bitumen content content and and glass glass contentcontent on on BFI BFI of of Mix Mix II IIcontaining containing 25% 25% RCA RCA without without Figureglass and 20. Mix Effect IV ofand bitumen Mix V contentcontaining and 25% glass RCA content as coarse on BFI aggregate of Mix II and containing glass as 25%fine aggregate.RCA without glassglass and Mixand Mix IV andIV and Mix Mix V containingV containing 25% 25% RCARCA as coarse aggregate aggregate and and glass glass as fine as ﬁne aggregate. aggregate.

Figure 21. Effect of bitumen content and glass content on BFI of Mix III containing 50% RCA without Figure 21. Effect of bitumen content and glass content on BFI of Mix III containing 50% RCA without Figureglass 21. andEffect Mix of VI bitumen and Mix contentVII containing and glass 50% contentRCA as coarse on BFI aggregate of Mix III and containing glass as fine 50% aggregate. RCA without glass and Mix VI and Mix VII containing 50% RCA as coarse aggregate and glass as fine aggregate. glass and Mix VI and Mix VII containing 50% RCA as coarse aggregate and glass as fine aggregate. As can be observed in Figures 20 and 21, both samples containing glass have slightly higher binderAs filmcan bethickness observed than in samplesFigures 20without and 21, glass. both However,samples containing the comparison glass have of samples slightly athigher their Asbinderoptimum can film be bitumen observedthickness content than in Figures samplesshows 20 thatwithout and BFI 21 ,glass.for both sa mplesHowever, samples containing the containing comparison 20% glassglass of havesamplesis less slightly than at their the higher binderoptimumminimum film thickness bitumenrequirements thancontent of samples 7.5 shows microns. withoutthat BFI glass.for samples However, containing the comparison 20% glass is of less samples than the at their optimumminimum bitumen requirements content showsof 7.5 microns. that BFI for samples containing 20% glass is less than the minimum requirements4.5. Volumetric of 7.5 Analysis microns. of Asphalt Mixtures at Optimum Bitumen Content 4.5. Volumetric Analysis of Asphalt Mixtures at Optimum Bitumen Content The results of volumetric properties evaluation of asphalt mixtures with different 4.5. VolumetriccombinationsThe results Analysis of aggregates of of Asphaltvolumetric at their Mixtures propertiesoptimum at Optimum conten evaluat are Bitumention presented of Contentasphalt in Table mixtures 9. As shown with indifferent Table 9, combinationsthe results of theof aggregates tests on asphalt at their mixtures optimum reveal conten thatt are all presentedmixtures madein Table of RCA9. As meetshown the in standard Table 9, Thethe results results of of the volumetric tests on asphalt properties mixtures evaluation reveal that of all asphalt mixtures mixtures made of with RCA different meet the combinationsstandard of aggregateslimits for volumetric at their optimum properties. content However, are their presented high bitumen in Table absorption9. As shown necessitates in Table the9, study the results of limitsvolumetric for volumetric properties properties. of asphalt However,mixtures madetheir hiwighth bitumenRCA in combinationabsorption necessitates with recycled the glass.study Toof of the tests on asphalt mixtures reveal that all mixtures made of RCA meet the standard limits for volumetricthis point, asproperties can be observed of asphalt in mixtures Table 9, madeall asphalt with RCAmixtures in combination containing RCAwith recycledand 10% glass.recycled To volumetric properties. However, their high bitumen absorption necessitates the study of volumetric thisglass point, meet as the can Australian be observed Standards’ in Table requirem9, all asphaltents mixturesand therefore containing are deemed RCA and appropriate 10% recycled for propertiesglassconsideration meet of asphalt the as Australianasphalt mixtures mix Standards’ design. made withIn addition,requirem RCA inresultsents combination and for thereforesamples with withare recycled RCAdeemed and glass. appropriate50% of To recycled this for point, as canconsiderationglass, be observed except asfor inasphalt binder Table mix9film, all design. asphaltindex Inand mixturesaddition, VMA (wresults containinghich forare samples shown RCA andwithin bold 10%RCA in recycledand Table 50% 9), of glass meetrecycled meet the the Australianglass,standard Standards’except typical for values.binder requirements filmHowever, index and VMAand therefore VMAfor thes are(wehich deemedsamples are shown appropriateare within in bold the for inAustralian considerationTable 9), Standardsmeet as the asphalt mix design.standardlimits. To In typicalthis addition, point, values. it results can However, be forconcluded samples VMA that for with asphaltthes RCAe samples mixtures and50% are containing within of recycled the 25% Australian glass,RCA and except Standards10% forglass binder limits. To this point, it can be concluded that asphalt mixtures containing 25% RCA and 10% glass film indexare the and most VMA comparable (which mixtures are shown with in control bold in samples. Table9), meet the standard typical values. However, are the most comparable mixtures with control samples. VMA for these samples are within the Australian Standards limits. To this point, it can be concluded that asphalt mixtures containing 25% RCA and 10% glass are the most comparable mixtures with control samples. Materials 2018, 11, 1053 20 of 25

Table 9. Volumetric properties of asphalt mixtures at optimum bitumen content.

Optimum Bitumen Bulk Density Binder Film Filler-Binder Specimen Name VMA (%) VFB (%) Content (%) (gr/cm3) Index (µm) Ratio Materials 2018, 11, x FOR PEER REVIEW 20 of 25 B100 5.1 2.442 15.5 71.5 7.8 1.1 B75 5.8 2.411 15.6 72.0 7.9 0.9 Table 9. Volumetric Properties of Asphalt Mixtures at Optimum Bitumen Content. B75-G10 5.4 2.398 15.0 70.5 7.5 1.0 B75-G20Optimum 5.3 Bitumen Bulk Density 2.390 14.5 69.5Binder Film 7.1 Filler-Binder1.0 Specimen Name VMA (%) VFB (%) B50Content 6.2 (%) (gr/cm 2.3683) 15.9 72.2Index (µm) 8.2Ratio 0.9 B50-G10B100 5.95.1 2.442 2.365 15.5 15.271.5 70.87.8 7.61.1 0.9 B50-G20B75 5.65.8 2.411 2.355 15.6 14.6 72.0 69.5 7.9 7.1 0.9 1.0 StandardB75-G10 Limit 5.4- 2.398 -15.0 13–20% 70.5 60–80%7.5 - 1.0 0.8–1.2 TypicalB75-G20 Value 5.3- 2.390 -14.5 15% (min)69.5 7.1 7.5 µm (min)1.0 - B50 6.2 2.368 15.9 72.2 8.2 0.9 B50-G10 5.9 2.365 15.2 70.8 7.6 0.9 In addition,B50-G20 for all samples5.6 at different 2.355 rates of bitumen14.6 content,69.5 as presented7.1 in Tables1.0 7 and8, it canStandard be observed Limit that increasing- the bitumen- content13–20% results60–80% in the specimen- height0.8–1.2 reduction. Typical Value - - 15% (min) 7.5 µm (min) - This effect can be due to the extra lubrication provided by the hot bitumen during compaction leading to the betterIn addition, and quicker for all compaction samples at different for the samerates of compactive bitumen content, effort. as presented in Tables 7 and 8, it can be observed that increasing the bitumen content results in the specimen height reduction. 4.6. ResilientThis effect Modulus can be of due Asphalt to the Mixtures extra lubrication at Optimum provided Bitumen by Contentthe hot bitumen during compaction Itleading has been to the well better established and quicker thatcompaction predicting for the the same performance compactive ofeffort. asphalt mixtures containing recycled materials is very difﬁcult given the inconsistency of materials and their complex interaction 4.6. Resilient Modulus of Asphalt Mixtures at Optimum Bitumen Content with natural materials. Therefore, in this research, primary tests were conducted on different mixtures in terms ofIt materialshas been well combinations established as that well predicting as the materials the performance amount. of asphalt mixtures containing recycled materials is very difficult given the inconsistency of materials and their complex Based on the result of the primary tests, the most acceptable samples were selected for estimating interaction with natural materials. Therefore, in this research, primary tests were conducted on their resilient modulus through the indirect tensile test for three specimens selected based on the different mixtures in terms of materials combinations as well as the materials amount. results ofBased primary on tests,the result as presented of the primary in Table tests, 10. the most acceptable samples were selected for estimating their resilient modulus through the indirect tensile test for three specimens selected based onTable the results 10. Material of primary combination tests, as presented for preparation in Table of specimens10. of indirect tensile test.

Table 10. MaterialCoarse combination Aggregate for preparation (%) Fine of specimens Aggregate of (%) IndirectOptimum Tensile Test. Bitumen Asphalt Mixture Basalt RCA Basalt Glass Content (OBC, %) Coarse Aggregate (%) Fine Aggregate (%) Asphalt Mixture Optimum Bitumen Content (OBC, %) B100Basalt 100RCA Basalt 0 Glass 100 0 5.1 B100 B75100 750 100 25 1000 0 5.1 5.8 B75-G10 75 25 90 10 5.4 B75 75 25 100 0 5.8 B75-G10 75 25 90 10 5.4 To conduct the resilient modulus test, a triaxial repeated loading machine capable of applying 50 kPa ofTo loading conduct was the usedresilient considering modulus test, repeated a triaxial haversine repeated loading loading. machine Using capable this machine, of applying the test 50 kPa of loading was used considering repeated haversine loading. Using this machine, the test sequence can be monitored through the user-friendly program and all test outputs are sent to a desktop sequence can be monitored through the user-friendly program and all test outputs are sent to a computerdesktop (Figure computer 22). (Figure 22).

Figure 22. Sample output of Resilient Modulus Test. Figure 22. Sample output of Resilient Modulus Test.

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The results of resilient modulus test conducted on three specimens from each asphalt mixture type are presented in Table 11.

Table 11. Result of resilient modulus test in accordance with AS 2891.13.1 (2013).

Asphalt Ave. Sample Ave. Sample Peak Recovered Horizontal Mr Mixture Height (mm) Diameter (mm) Load (N) Strain (µε) (MPa) B100 64.95 99.925 2718.7 50.01 5613 B75 68.225 99.95 3252.7 51.52 6205 B75-G10 68.025 99.975 3302.6 49.08 6632

As presented in Table 11, the resilient modulus obtained for the sample containing 10% glass is about 15% higher than the measured values for the conventional asphalt mixtures. These results show that the utilization of waste glass and RCA in asphalt mixtures combine the advantages of producing a better asphalt pavement as well as the waste management problem, which subsequently provides a reduction in cost and resources demand. It should be mentioned that the coefficient of variation is used as an indication to measure the heterogeneity of test results. The results of calculation of standard deviation (SD) and coefficient of variation (COV) for test results provided in Table 11, has shown that the coefficient of variation and standard deviation for the data sets were in an acceptable range of 1.05 to 2.02 (for coefficient of variation) and 0.023 to 0.134 (for standard deviation), revealing that the test results dispersion is low and the tests are conducted consistently.

5. Further Research Although many laboratory and ﬁeld investigations have been already performed on the performance of asphalt mixtures made with recycled materials such as RCA and recycled glass, more studies are still required to deal with the challenges of this sustainable approach for further use. In this regard, a set of recommendations are provided for researching the engineering properties and other aspects of this technology, as follows: The incorporation of waste glass in asphalt mixtures affects the bitumen absorption of mixtures, and therefore can compensate for the high bitumen-absorbing RCA. This research investigated the effect of glass on asphalt mixtures containing RCA considering three different percentages. However, it is recommended to investigate the effect of glass size, colours of glass and the glass content in asphalt mixtures. Further investigation is required on the fatigue behaviour and also the ageing of asphalt mixtures containing RCA and glass.

6. Conclusions This research project was aimed at investigating the feasibility of using recycled glass for compensation of high bitumen absorption of asphalt mixtures containing RCA. The test results on aggregates and asphalt mixtures containing RCA with/without glass indicate that:

(1) RCA has lower ﬂakiness index and misshapen particles compared to basalt implying that asphalt mixtures with a certain amount of RCA can provide better workability, compaction and rutting resistance. (2) RCA has considerably higher water absorption and wet/dry strength variation in comparison with the virgin aggregate. The results of tests conducted on RCA showed that RCA still meets the standards requirements for aggregates in asphalt mixtures. However, the high water absorption of RCA should be compensated. (3) Asphalt mixtures containing RCA have a lower bulk density, VMA, VFB and BFI than control mixes, whereas the air voids are higher for mixtures containing RCA. Lower bulk density of RCA Materials 2018, 11, 1053 22 of 25

will result in cost reduction, as asphalt jobs are mostly measured in cubic meter and materials are purchased in tonnes. (4) The results of tests on different asphalt mixtures containing different percentages of RCA indicated that RCA increase results in an increase in the optimum bitumen content of the mixtures. Hence, the selection of a proper combination of RCA and other aggregates is required for satisfying the relevant standard requirements. (5) Utilization of recycled glass with very low water absorption in asphalt mixtures with different combinations of RCA were observed to reduce the bitumen absorption of these asphalt mixtures. (6) The results of tests on different asphalt mixtures containing RCA and glass indicate that the bitumen absorption decreases with glass increase in asphalt mixtures. In other words, asphalt mixtures containing glass have a lower optimum bitumen content in comparison with asphalt mixtures without glass. So that, as presented in Table8, asphalt mixtures containing 75% RCA with 10% and 20% glass have optimum bitumen content very close to the optimum content of control samples (asphalt mixtures without any recycled materials). (7) The results of tests on asphalt mixtures containing RCA and glass at different rate of bitumen content reveals that air void, VMA and bulk density are lower than the corresponding values for asphalt mixtures containing RCA without glass, whereas introducing glass in the asphalt mixtures increases VFB in asphalt mixtures containing both RCA and glass than asphalt mixtures containing only RCA. (8) The results of volumetric properties of all asphalt mixtures at their optimum bitumen content, as shown in Table9, indicates that asphalt mixtures made by combining 25% RCA and 10% glass is the most comparable mixture to control samples in terms of volumetric properties and optimum bitumen content requirements. (9) The results of the resilient modulus test on selected asphalt mixtures reveals that asphalt mixtures made of 25% RCA and 10% glass have about 15% more stiffness than conventional mixtures. (10) Since the resilient moduli of asphalt mixtures is an important parameter in characterization of the entire structural performance of pavement affecting the layer thickness, the service life and the overall cost of pavement construction, the result of the resilient modulus test indicates that asphalt mixtures made of a combination of 25% RCA and 10% glass will result in the improvement of the structural performance of asphalt pavements as well as the environmental and economic advantages.

Author Contributions: F.T. is the main author and researcher conducting this research as the main component of her PhD studies, B.S. has directed and coordinated the project in a supervisory capacity, J.Y. and R.C. have been consultants to the project providing valuable insights into behavior of asphalt mixtures containing recycled materials. Funding: This research received no external funding. Acknowledgments: The authors would like to acknowledge Boral Asphalt Company for providing part of materials required for the research work and their technical assistance. Conﬂicts of Interest: The authors declare no conﬂict of interest.

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