The Use of Glass to Optimize Bitumen Absorption of ...

materials 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 2 3

*

Centre for Infrastructure Engineering, Western Sydney University, Penrith, NSW 2751, Australia; [email protected] Faculty of Science, Health, Education and Engineering, University of Sunshine Coast, Sippy Downs, QLD 4556, Australia; [email protected] 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

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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 demand2018, reduction Materials 11, 1053 for virgin aggregates is another advantage resulting in subsequent economic 2 of 25 advantages. However, developing a suitable mix design containing RCA and glass is necessary before However, design containing and glass necessary before employing this developing technology ainsuitable asphalt mix mixture production. TheRCA purpose of theispresent work is to employing this technology in asphalt mixture production. The purpose of the present work is study the benefit of glass addition on the bitumen absorption of asphalt mixtures containing RCA to benefit ofthe glass addition on the bitumen of asphalt containing in study order the to optimize RCA-contained asphalt mix absorption design. In that sense, mixtures as discussed in the RCA in order to optimize the RCA-contained asphalt mix design. In that sense, as discussed in the following sections, several tests were conducted on individual aggregates in order to obtain further following sections, several tests were conducted on individual aggregates in order to obtain further knowledge on the recycled aggregate properties as well as to compare them with the corresponding knowledge on the the recycled aggregateand properties as well as to compare them properties of virgin aggregate the standards requirements. Basedwith on the the corresponding results of the properties of the virgin aggregate and the standards requirements. Based on the results of the aggregate aggregate specification tests, different tests were conducted on asphalt mixtures containing various specification differentand testsrecycled were conducted on asphalt mixtures containingtheir various combinations combinationstests, of natural aggregates in order to investigate performance in of natural and recycled aggregates in order to investigate their performance in asphalt mixture and asphalt mixture and to characterize the effects of glass on the bitumen absorption and volumetric to characterize the effects of glasscontaining on the bitumen absorption and volumetric of asphalt properties of asphalt mixtures different percentages of RCA. properties The findings of the mixtures containing different percentages of RCA. The findings of the experimental work are given in experimental work are given in three main sections including the mechanical and physical three main sections including the mechanical and physical properties of coarse aggregates (i.e., RCA properties of coarse aggregates (i.e., RCA and basalt), the physical characteristics of fine aggregates and thebasalt) physical of fine aggregates (i.e.,Asphalt glass and basalt) and volumetric (i.e., basalt), glass and andcharacteristics volumetric performance of Hot Mix (HMA) containing RCA in performance of Hot Mix Asphalt (HMA) containing RCA in combination with glass and without combination with glass and without glass. Figure 1 illustrates the flowchart of discussion inglass. this Figure 1 illustrates the flowchart of discussion in this research work. research work.

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

2. Background Background 2. Today,many manywaste wastematerials materialssuch suchasastyres, tyres,plastics, plastics, waste glass, etc. used construction Today, waste glass, etc. areare used forfor construction of of different layers of pavements including the asphalt surface layer [3–14]. Utilization solid different layers of pavements including the asphalt surface layer [3–14]. Utilization of solidofwastes wastes in the layer asphalt not onlythe reduces theimpacts adverse of waste also the in the asphalt notlayer only reduces adverse of impacts waste disposal butdisposal also the but demand for demand for natural materials which will subsequently results in cost savings and economic natural materials which will subsequently results in cost savings and economic advantages. Moreover, advantages. Moreover, using in thethe recycled in thecan asphalt surface contribute of to using the recycled materials asphaltmaterials surface layer contribute to layer more can improvement more improvement of engineering characteristics of the asphalt pavement materials, representing engineering characteristics of the asphalt pavement materials, representing a value-added applicationa value-added application wastes. However, the selection of waste materialsparticularly used for road for solid wastes. However,for thesolid selection of waste materials used for road construction, the construction, particularly the surface course, is of high importance as the incorporation of wastes surface course, is of high importance as the incorporation of wastes should not affect the functional should not affect the functional and structural aspects of the pavements [15–17]. and structural aspects of the pavements [15–17]. In addition, due to the importance of the aggregates in in asphalt asphalt concrete, concrete, the the studies studies on on the the In addition, due to the importance of the aggregates utilization ofofthethe recycled aggregates such as reclaimed asphalt pavement (RAP), recycled utilization recycled aggregates such as reclaimed asphalt pavement (RAP), recycled construction construction aggregate (RCA), recycled glass, etc. have increased worldwide over the past two aggregate (RCA), recycled glass, etc. have increased worldwide over the past two decades [18–20]. decadesthe [18–20]. Among the recycled aggregates, large amount of demolition construction and generation demolition Among recycled aggregates, the large amount the of construction and waste waste generation worldwide justifies the idea of using RCA in new asphalt mixtures. Referring to worldwide justifies the idea of using RCA in new asphalt mixtures. Referring to available literature 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.

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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

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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 Table 1, 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

Increased road safety

Since the glass particles have low water absorption, the pavement surface gets dry faster after rain

Easier to compact and cartage over longer distance

Glass asphalt mixtures hold heat longer compared to conventional asphalt mixtures

Improved night time road visibility

Glass asphalt surfaces are more reflective in comparison with conventional asphalt surfaces

Waste reduction

Glass wastes are not disposed into the landfills offering environmental benefits and saving costs

Improved workability

The presence of long and flat particles will positively affect the workability of asphalt mixtures

Commercial benefits

Raw materials are replaced by glass resulting in savings on costs of materials

No need to change asphalt paving process

The same construction method used for conventional asphalt mixtures can be 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

Stripping problem

The smooth surface of glass particles reduces the adhesion of asphalt film to the crushed glass, which may cause stripping of the asphalt mixture.

Decreased transverse stability

Sensitive to water damage

Abrasion of tires Decreased skid resistance

The angularity and friction angle of glass particles provides inadequate transverse stability, particularly at braking or start-up The high silica content in glass particles will make asphalt mixtures made with 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 particles size) may result in abrasion of tires High amount of large size glass particles cause a decrease in skid resistance

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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 Table 2. Table 2. Characteristics of the original bitumen. Characteristics

Unit

Methods

Value

Softening point Penetration at 25 ◦ C Flashpoint Viscosity at 60 ◦ C Viscosity at 135 ◦ C Specific Gravity

◦C

AS 2341.18 [55] AS 2341.12 [56] AS 2341.14 [57] AS 2341.2 [58] AS 2341.2 [58] AS 2341.7 [59]

52 min 40 min 250 320 0.5 1.03

dmm ◦C Pa·s Pa·s Kg/m3

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).

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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 Table 3. Table 3. Bitumen and aggregate mix combination rates. Coarse Aggregate (%) RCA

Basalt

Bitumen Content (%)

B100-4.5 B100-5 B100-5.5

0 0 0

100 100 100

Mix II

B75-5 B75-5.5 B75-6

25 25 25

Mix III

B50-5 B50-5.5 B50-6 B50-6.5

Mix IV

Mix Name

Specimen Name

Mix I

Fine Aggregate (%) Glass

Basalt

4.5 5 5.5

0 0 0

100 100 100

75 75 75

5 5.5 6

0 0 0

100 100 100

50 50 50 50

50 50 50 50

5 5.5 6 6.5

0 0 0 0

100 100 100 100

B75-G10-5 B75-G10-5.5 B75-G10-6

25 25 25

75 75 75

5 5.5 6

10 10 10

90 90 90

Mix V

B75-G20-5 B75-G20-5.5 B75-G20-6

25 25 25

75 75 75

5 5.5 6

20 20 20

80 80 80

Mix VI

B50-G10-5 B50-G10-5.5 B50-G10-6

50 50 50

50 50 50

5 5.5 6

10 10 10

90 90 90

Mix VII

B50-G20-5 B50-G20-5.5 B50-G20-6

50 50 50

50 50 50

5 5.5 6

20 20 20

80 80 80

Figure 2 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).

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Figure Gradation curve curve of Figure 2.2.Gradation ofasphalt asphaltmixtures. 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

It is generallyThe recognized the volumetric composition of mixtures greatly influence performance. volumetricthat properties evaluation of asphalt mixtures is the fundamental of their asphalt mix determining theevaluation performance of asphalt mixture. asphalt mixture performance. The design, volumetric properties of asphalt mixtures is theThe fundamental of asphalt volumetric properties including void content, filled with binder and mixture voids in mineral mix design, determining the performance of voids asphalt mixture. The(VFB) asphalt volumetric aggregate (VMA) have been recognized as important parameters affecting the durability and properties including void content, voids filled with binder (VFB) and voids in mineral aggregate performance of asphalt pavements [62]. The minimum values are typically required for volumetric (VMA) have been recognized as important parameters affecting the durability and 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) depending the asphalt type. with a on nominal size of mixture 14 (AC14), which are prepared in accordance with Test Method RMS T661 As mentioned previously, all asphalt in this research areidentical dense-graded asphalt[60] (DGA) [63] and RMS T662 [64] (120 cycles ofmixes compaction) which are to AS2891.2.1 and with a nominal size of 14 respectively. (AC14), which prepared in Test Method RMSofT661 [63] and AS2891.2.2 [61], Theare requirements foraccordance volumetric with parameters of this type mixture RMS are T662 [64] (120 cycles of 4. compaction) are identical to AS2891.2.1 [60] andthe AS2891.2.2 summarized in Table In addition, which a summary of the tests carried out to study mixtures [61], properties is explained in the for following sections. respectively. The requirements volumetric parameters of this type of mixture are summarized in Table 4. In addition, a summary of the tests carried out to study the mixtures properties is explained in Table 4. Volumetric Parameters Requirements for DGA AC14 (AS2150-2005). the following sections. Parameter Air Void Table 4. VMA VFB Parameter Binder Air FilmVoid Index VMARatio Filler-Binder VFB

Bulk Density Test

Binder Film Index

Range

Typical Values

Description

3–6% 5% Mixtures in accordance with RMS T662 Volumetric parameters requirements for prepared DGA AC14 (AS2150-2005). 13–20% 65–80% Range - 3–6% 13–20% 0.8–1.2 65–80% -

≥ 15 Mixtures prepared in accordance with RMS T662 accordance with RMS T662 Typical Values Mixtures prepared inDescription Determined in accordance with Test Method Mixtures prepared in accordance with RMS T662 ≥ 7.5 μm5% Austroads AG:PT/T237 or AS 2891.8 ≥ 15 Mixtures prepared accordance with RMS T662 Mixtures prepared in in accordance with RMS T662 Mixtures prepared in accordance with RMS T662

≥7.5 µm

Determined in accordance with Test Method Austroads AG:PT/T237 or AS 2891.8

In this research, the bulk density of compacted samples is determined using the presaturation Filler-Binder Ratio 0.8–1.2 preparedisin suitable accordance RMS T662 procedure in accordance with AS/NZS 2891.9.2 [65].Mixtures This method forwith dense-graded mixtures with internal air voids that are largely inaccessible to moisture resulting in low Bulk permeability. Density Test Maximum Densitythe Testbulk density of compacted samples is determined using the presaturation In this research, procedureInin this accordance withmaximum AS/NZS density 2891.9.2of [65]. This method dense-graded study, the a loose sample is ofsuitable mix is for determined using mixtures the procedure, in accordance with resulting AS/NZS 2891.7.3 Based on this with methylated internal airspirits voidsdisplacement that are largely inaccessible to moisture in low [66]. permeability. test method, firstly, the density of methylated spirit (ρ ) was determined as 0.789 t/m3.

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, firstly, the density of methylated spirit (ρm ) was determined as 0.789 t/m3 .

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Voids and Volumetric Properties VoidsThe andvoids Volumetric Propertiesproperties of asphalt mixtures are determined, in this research, in and volumetric accordance withand AS/NZS 2891.8 [67]. The voids volumetric 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 determining the performance of asphalt underproperty traffic loading. Thean resilient modulus is The stiffness of asphalt mixtures is pavement a fundamental and plays important role in the measure of of asphalt mixtures. In addition, resilient modulus of asphalt mixtures determining thestiffness performance of asphalt pavement underthe traffic loading. The resilient modulus is is useful in determination of layer thickness through estimation of the relative strength coefficient the measure of stiffness of asphalt mixtures. In addition, the resilient modulus of asphalt mixtures is and calculation of Structural Number (SN).through estimation of the relative strength coefficient and useful in determination of layer thickness In thisofstudy, resilient modulus calculation Structural Number (SN). test was considered for evaluation of the stiffness of some specimens based onmodulus the results of was a primary test tofor assess the effect thestiffness RCA amount as In thisselected study, resilient test considered evaluation ofofthe of some well as the selected asphalt mixture onaresilient To this asphalt specimens based oncomposition the results of primarymodulus. test to assess thepoint, effect the of the RCAmixtures amount were prepared using different combinationson but with the same gradation. Subsequently, themixtures asphalt as well as the asphalt mixture composition resilient modulus. To this point, the asphalt mixtures were using compacted with GyroPac atbut the same of compaction to make the cylindrical were prepared different combinations with the level same gradation. Subsequently, asphalt specimens of 100 mm in diameter and 65 in height. mixtures were compacted with GyroPac atmm the same level of compaction to make cylindrical specimens The modulus, thisinresearch, of 100 mmresilient in diameter and 65inmm height. was determined through an indirect tensile strength test in with AS/NZS 2891.13.1was [68]. In this test, firstly, the diameter and height Theaccordance resilient modulus, in this research, determined through an indirect tensile strength test of in specimens measured. The specimen wastest, placed in the diameter temperature-controlled cabinet atwere the accordance were with AS/NZS 2891.13.1 [68]. In this firstly, and height of specimens ◦C temperature of specimen 25 °C to allow the temperature in the specimen to reach equilibrium prior to of the25test. measured. The was placed in the temperature-controlled cabinet at the temperature Then, andinLinear Variable Differential Transformers were to to allowthe themachine temperature the specimen to reach equilibrium prior to the(LVDT) test. Then, thecalibrated machine and conduct the test. Linear Variable Differential Transformers (LVDT) were calibrated to conduct the test. During the test, test, repeated repeatedhaversine haversineloading loadingisisapplied appliedtoto specimen at the frequency of Hz 0.1 thethe specimen at the frequency of 0.1 Hz considering s loading s rest period (Figure considering 0.1 s0.1 loading andand 0.9 s0.9 rest period (Figure 3). 3).

Figure Figure 3. Load Load 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:

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Mr = P ×

(µ + 0.27) H × hc

(1)

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

Test

Test Method

Flakiness Index Test Particle Shape Test Water Absorption Particle Density Particle Density on Dry Basis Particle Density on SSD Basis Aggregate Crushing Value Weak Particles Wet/Dry Strength Test Wet Strength Dry Strength

AS 1141.15 [69] AS 1141.14 [70] AS 1141.6.1 [71] AS 1141.6.1 [71] AS 1141.6.1 [71] AS 1141.6.1 [71] AS 1141.21 [72] AS 1141.32 [73] AS 1141.22 [74] AS 1141.22 [74] AS 1141.22 [74]

RCA

Basalt

Typical Limit Based on Australian Standards

6.9 6.2 6.30 2.370 2.212 2.351 29.21 0.23 26.6 119.7 163.1

19.0 18.3 1.64 2.640 2.530 2.571 8.91 0.23 8.5 359.2 392.9

25% (max) 35% (max) 2% (max) 35% (max) 1% (max) 35% (max) 150 kN (min) -

As can be observed in Table 5, 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 Table 5, 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 Table 6. The data given in Table 4 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.

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Table 6. Test results for evaluation of fine aggregate properties. Aggregate 10 on of 25 Typical Limit Based Australian Standards Glass Basalt Table 6. Test Results for Evaluation of0.10 Fine Aggregate Water Absorption AS 1141.5 [75] 2.35Properties. 3% (max) Particle Density AS 1141.5 [75] 2.489 2.879 Aggregate Typical Limit Based on Particle Density AS 1141.5 [75] 2.483 2.610 Teston Dry Basis Test Method Australian- Standards Glass Basalt Particle Density on SSD Basis AS 1141.5 [75] 2.485 2.668

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Test

Test Method

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 Particle Density on SSD Basis of AS [75] 2.485 2.668 were determined The volumetric properties the1141.5 basalt-RCA asphalt mixtures and then

compared with the standards specifications. According to Austroads (2014), the essential parameters Volumetric Analysis Asphalt Mixtures in the4.3. level 1 of mix designofinclude air voids,Containing voids in RCA mineral aggregate (VMA), and voids filled with The volumetric properties of the basalt-RCA asphalt mixtures were determined and then binder (VFB), [76]. compared with thethe standards specifications. According Austroads (2014), the essential parameters Table 7 presents properties obtained for asphalttomixtures with different bitumen content and in the level 1 of mix design include air voids, voids in mineral aggregate (VMA), and voids filled aggregate combination at a selected level of gyrations (120 cycles). with binder (VFB), [76]. Table 7 presents theTable properties obtained for asphalt mixtures with different bitumen content 7. Volumetric properties of asphalt mixtures. and aggregate combination at a selected level of gyrations (120 cycles).

Specimen Name

AV (%)

B100-4.5 Specimen Name B100-5 B100-5.5 B100-4.5 B100-5 B75-5 B100-5.5 B75-5.5 B75-5 B75-6 B75-5.5 B50-5 B75-6 B50-5.5 B50-5 B50-6 B50-5.5 B50-6.5

7.2 5.4 4.1 6.7 5.4 4.8 7.3 6.0 5.4 4.5

B50-6 B50-6.5

Water Bulk Density VMA VFB Binder Film Mixtures. AbsorptionTable (%) 7. Volumetric (gr/cm3 ) Properties (%) of Asphalt (%) Index (µm) AV (%) 7.2 5.4 4.1 6.7 5.4 4.8 7.3 6.0 5.4 4.5

0.46 Water Absorption (%) 0.17 0.110.46 0.430.17 0.230.11 0.150.43 0.560.23 0.310.15 0.240.56 0.160.31 0.24 0.16

2.398 Bulk Density (gr/cm3) 2.439 2.441 2.398 2.439 2.398 2.441 2.410 2.398 2.411 2.410 2.355 2.411 2.371 2.355 2.373 2.371 2.359 2.373 2.359

16.4 VMA (%) 15.4 15.8 16.4 15.4 15.3 15.8 15.3 15.3 15.7 15.3 15.3 15.7 15.1 15.3 15.5 15.1 16.5 15.5 16.5

59.6 VFB (%) 69.0 78.6 59.6 69.0 59.7 78.6 68.7 59.7 73.8 68.7 55.3 73.8 64.0 55.3 69.1 64.0 77.1 69.1 77.1

6.9 Film Binder Index 7.5 (µm) 8.76.9 6.47.5 7.48.7 8.26.4 5.97.4 6.88.2 7.55.9 9.06.8 7.5 9.0

Filler-Binder Ratio 1.2 Filler-Binder Ratio 1.1 1.0 1.2 1.1 1.1 1.0 1.0 1.1 0.9 1.0 1.1 0.9 1.0 1.1 0.9 1.0 0.9 0.9 0.9

Height (mm) 69.0 Height (mm) 67.0 66.3 69.0 67.0 69.7 66.3 67.6 69.7 67.0 67.6 73.6 67.0 71.0 73.6 68.9 71.0 68.2 68.9 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 To determine the optimum bitumen content for theinasphalt mixture, the procedure indicated by Australian standards, AGPT04B-14, was followed this research. Three specimens at each by Australian standards, AGPT04B-14, was followed in this research. Three specimens at each bitumen content (4.5%, 5%, 5.5%, 6%, and 6.5%) were tested for maximum density, bulk 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 determine the optimum bitumen content that provides air voids within the specified limits and used to determine the optimum bitumen content that provides air voids within the specified limits VMAand near to the minimum value. According to the to results obtained, Figure 4 illustrates the effect of VMA near to the minimum value. According the results obtained, Figure 4 illustrates the bitumen andcontent RCA content oncontent air voids of asphalt effectcontent of bitumen and RCA on air voids of mixtures. asphalt mixtures.

Figure 4. Effect of bitumen content and RCA content on air voids of Mix I containing virgin

Figure 4. Effect of bitumen content and RCA content on air voids of Mix I containing 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 air mix is aisfunction of bitumen content, degree of compaction and VMA. air void voidcontent contentininthe the mix a function of bitumen content, degree of compaction and The air void percentage in the mixture affects mix stiffness, fatigue resistance, and durability. As shown VMA. The air void percentage in the mixture affects mix stiffness, fatigue resistance, and durability. in figure, air voids with the bitumen content increase. Air voids ofAir mixtures made with Asthis shown in this figure,decrease air voids decrease with the bitumen content increase. voids of mixtures RCA substantially higher than the control mixtures because of porous cement paste attached the madeare with RCA are substantially higher than the control mixtures because of porous cement to paste virgin aggregates and also porous structure of some aggregates in the RCA. attached to the virgin aggregates and also porous structure of some aggregates in the RCA. Generally, have thethe lowest practical air voids in order to reduce the binder Generally,asphalt asphaltmixtures mixturesshould should have lowest practical air voids in order to reduce the ageing the and permeability and subsequent stripping stripping problems. problems. However, However, referring toreferring Austroads binder and ageing the permeability and subsequent to (2014), plastic flow and subsequent bleeding, flushing, shovingflushing, or permanent deformation of the Austroads (2014), plastic flow and subsequent bleeding, shoving or permanent pavement mayofoccur the air voids areoccur too low thanvoids about are 2%).too Accordingly, can be observed deformation the ifpavement may if (less the air low (lessasthan about 2%). in Figure 4, some of be theobserved mixturesin (i.e., B100-4.5, B75-5 andmixtures B50-5) cannot be acceptable terms of Accordingly, as can Figure 4, some of the (i.e., B100-4.5, B75-5 in and B50-5) air voids discussed the optimum can bethe obtained for cannot berequirements. acceptable inAs terms of air previously, voids requirements. As bitumen discussedcontent previously, optimum design aircontent voids ofcan 5%.beBased on the results, content wasresults, found to 5.1% for bitumen obtained for designthe airoptimum voids ofbitumen 5%. Based on the thebeoptimum reference sampleswas (0% found RCA), to 5.8% samples with 25% RCA and for5.8% samples with 50%with RCA, as bitumen content be for 5.1% for reference samples (0%6.2% RCA), for samples 25% illustrated in Figure 4. RCA and 6.2% for samples with 50% RCA, as illustrated in Figure 4. Furthermore, VMA is another important volumetric volumetric property which should be checked for selection of thethe combination of air voids in the mix mix and of the thefinal finalbitumen bitumencontent. content.VMA VMAis is combination of air voids in compacted the compacted the occupied by the binder which is total binder minus any binder absorbed into andvolume the volume occupied byeffective the effective binder which is total binder minus any binder absorbed the VMA is a function of the and and the particle shape andand surface texture of the intoaggregate. the aggregate. VMA is a function of gradation the gradation the particle shape surface texture of aggregate particles. VMA should be large enough to provide a sufficient amount of air in the the aggregate particles. VMA should be large enough to provide a sufficient amount of voids air voids in compacted mixture for ensuring the asphalt mixturemixture stabilitystability while leaving for the binder the compacted mixture for ensuring the asphalt whileenough leavingspace enough space for to durability. VMA is too would be insufficient cohesion and theensure binderthe to mixture ensure the mixtureIfdurability. If low, VMAthe is binder too low, the binder would beforinsufficient for durability whereas too high VMA too results more results costly asphalt due to increased binder cohesion and durability whereas highinVMA in moremixtures costly asphalt mixtures due to volume tobinder satisfy volume the air voids requirements. increased to satisfy the air voids requirements. The variation of VMA Figure 5. VMA with with bitumen bitumen content contentfor forMix MixI,I,Mix MixIIIIand andMix MixIIIIIIare areshown showninin Figure As cancan be be observed in Figure 5, VMA increases with bitumen content afterafter a minimum point. The The test 5. As observed in Figure 5, VMA increases with bitumen content a minimum point. results on different samples showed that VMA mixtures containing RCA is RCA quite is a bit lower than the test results on different samples showed that of VMA of mixtures containing quite a bit lower control canwhich be as can a result bitumen of RCA resulting the lower than thesamples control which samples be asofahigher result of higherabsorption bitumen absorption of RCA in resulting in amount not-absorbed binder (effective illustrated in Figure 5, optimum the lowerofamount of not-absorbed binder binder). (effectiveAs binder). As illustrated in mixtures Figure 5, at mixtures at bitumen meet the requirements of 15% (minimum) for VMA. for VMA. optimumcontent bitumen content meet the requirements of 15% (minimum)

Figure 5. 5. Effect Effect of ofbitumen bitumencontent contentand andRCA RCA content VMA of Mix I containing virgin aggregate Figure content onon VMA of Mix I containing virgin aggregate and and Mix II and Mix III containing RCA as coarse aggregate. Mix II and Mix III containing RCA as coarse aggregate.

4.3.2. Determination and Water Water Absorption Absorption 4.3.2. Determination of of Bulk Bulk Density Density and 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 Figure 6. 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. 6. Effect of bitumen content and RCA content on bulk density density of of Mix Mix I containing containing virgin virgin Figure Effect of of bitumen bitumen content content and and RCA RCA content content on on bulk bulk Figure 6. Effect density of Mix II containing virgin aggregate and Mix II and Mix III containing RCA as coarse aggregate. aggregate and and Mix Mix II II and and Mix Mix III III containing containing RCA RCA as aggregate as coarse coarse aggregate. aggregate.

Furthermore, the experimental results show the water absorption increase of the mixtures by absorption increase of the mixtures by the Furthermore, the the experimental experimentalresults resultsshow showthe thewater water absorption increase of the mixtures by the increase in amount of RCA at the same bitumen content due to porous structure of RCA, as increase in amount of RCA at theat same contentcontent due to porous of RCA, as the increase in amount of RCA the bitumen same bitumen due to structure porous structure of expected RCA, as expected and shown in Figure 7. and shown inshown Figure in 7. Figure 7. expected and

Figure 7. Effect of bitumen content and RCA content on water absorption of Mix I containing virgin Figure 7. of content and content on absorption Figure 7. Effect Effect of bitumen bitumen content and RCA RCARCA content on water water absorption of of Mix Mix II containing containing virgin virgin aggregate and Mix II and Mix III containing as coarse aggregate. aggregate and Mix II and Mix III containing RCA as coarse aggregate. aggregate and Mix II and Mix III containing 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 of Voids Filled with Bitumen important volumetric parameter 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 ratio of theimportant effective binder (by volume) andisthe VMA. Mixtures with low VFBVFB are is dry and lack Another volumetric parameter voids filled with binder (VFB). defined as the ratio of the effective binder (by volume) and the VMA. Mixtures with low VFB are dry and lack durability, andbinder fatigue(by resistance. the ratio of cohesion the effective volume) and the VMA. Mixtures with low VFB are dry and lack durability, cohesion and fatigue resistance. These cohesion mixturesand mayfatigue also beresistance. more permeable, whereas asphalt mixtures with too high VFB can durability, These mixtures may also be more permeable, whereas asphalt mixtures with too high VFB can become unstable andmay susceptible to rutting. Figurewhereas 8 illustrates the mixtures variationwith of VFB These mixtures also be more permeable, asphalt too with high the VFBRCA can become unstable and susceptible to rutting. Figure 8 illustrates the variation of VFB with the RCA and bitumen content. The VFB values obtained asphalt mixtures containing become unstable and susceptible to rutting. Figurefor 8 illustrates the variation of VFBRCA with are the relatively RCA and and bitumen content. The VFB values obtained for asphalt mixtures containing RCA are relatively lower compared to the of higher absorption RCAareleading to lower a less bitumen content. The VFBcontrol valuessamples obtainedbecause for asphalt mixtures containingofRCA relatively lower compared to the control samples because of higher absorption of RCA leading to a less amount of not-absorbed binder (effective binder). compared to the control samples because 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 Mix8.IIEffect and Mix III containing RCA coarse aggregate. of bitumen content andasRCA content on VFB of Mix I containing virgin aggregate Mix IIFigure and Mix III containing RCA as coarse aggregate. and Mix II and Mix III containing RCA as coarse aggregate.

4.3.4. Determination of Binder Film Index (BFI)

4.3.4.4.3.4. Determination of Binder Film Determination of Binder FilmIndex Index(BFI) (BFI)

Binder Film Index (BFI) is another parameter that can be considered at the volumetric design

stageBinder asFilm a guide to the incorporation of sufficient binder in asphalt mixture tovolumetric ensure adequate Binder Index (BFI) is another parameter that cancan bethe considered atat the volumetric design Film Index (BFI) is another parameter that be considered the designstage durability, cohesion, resistance to the effects of moisture and fatigue resistance (Austroads, stage as a guide to the incorporation of sufficient binder in the asphalt mixture to ensure adequate as a guide to the incorporation of sufficient binder in the asphalt mixture to ensure adequate2014). durability, BFI isresistance a function the surface filler and the aggregates as well as the2014). effective durability, cohesion, resistance the of effects of moisture and fatigue resistance (Austroads, cohesion, toofthe effects oftoarea moisture and fatigue resistance (Austroads, BFIbitumen is 2014). a function content. to thesurface results obtained, theand binder film index as of Mix I,asMix II and Mix III are is a According function the of filler theasaggregates thecontent. effective bitumen of theBFI surface area of of filler and the area aggregates as well the effectivewell bitumen According to shown Figure 9. As observed in Figure 9, BFI values for Mix II and Mix IIIIIand are Mix lowerIIIthan content.inAccording to can the be results obtained, the binder film index of Mix I, Mix are the results obtained, the binder film index of Mix I, Mix II and Mix III are shown in Figure 9. As can be BFI for in control (Mix I) at the in same bitumen as Mix more binder absorbed bythan the shown Figuresamples 9. As can be observed Figure 9, BFIcontent, values for II and MixisIII are lower observed in Figure 9, BFI values for Mix II in and Mix III are lower than BFI fordue control samples (Mix mixtures incorporating RCA, resulting less aggregate particles coating to the reduction of I) at BFI for control samples (Mix I) at the same bitumen content, as more binder is absorbed by the the same bitumen content, as more binder is absorbed by the mixtures incorporating RCA, resulting available binder for thisRCA, purpose. As can be expected, BFI iscoating increased thereduction increase in mixtures incorporating resulting in less aggregatethe particles duewith to the of in less aggregate particles due to of available for this As in can be bitumen availablecontent. binder for coating this purpose. Asthe canreduction be expected, the BFI isbinder increased withpurpose. the increase expected, the BFI is increased with the increase in bitumen content. 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 Figure 9. Effect of bitumen content and RCAaggregate. content on BFI of Mix I containing virgin aggregate and

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. Mix IIInand Mix IIIas containing RCA coarse addition, can be seen in as Figure 9, aggregate. all samples at their optimum bitumen content meet the

minimum requirements of 7.5 µm BFI. 9, all samples at their optimum bitumen content meet the In addition, as can be seen in for Figure

In addition, as can be seen minimum requirements of 7.5 in µmFigure for BFI.9, all samples at their optimum bitumen content meet the 4.4. Volumetric Analysis of Asphalt Mixtures minimum requirements of 7.5 µm for BFI. Containing RCA and Glass 4.4. Volumetric Analysis of Asphalt Containing and Glass Since asphalt mixtures madeMixtures with RCA have theRCA problem of high absorption, as discussed in

4.4. Volumetric Analysisit ofis Asphalt Mixtures Containing RCA and Glass previous desired to optimize absorption characteristics of these asphalt mixtures Sincesections, asphalt mixtures made with RCAthe have the problem of high absorption, as discussed in by addingsections, recycleditglass, whichto the primary objective of this research work. previous is desired optimize absorption characteristics these asphalt Since asphalt mixtures made iswith RCAthe have the problem of high of absorption, as mixtures discussed in by adding recycled glass, which is the primary objective of this research work. previous sections, it is desired to optimize the absorption characteristics of these asphalt mixtures by adding recycled glass, which is the primary objective of this research work.

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To this 2018, end,11,different asphalt 10% Materials x FOR PEER REVIEWmixtures containing RCA with three glass contents of 0%, 14 of 25 and 20% (by weight of fine aggregates) were prepared for evaluating the effect of the addition of glass to To asphalt this end,mixtures. different asphalt with threeofglass contentsat ofdifferent 0%, 10% rates RCA-basalt For thismixtures purpose,containing different RCA combinations aggregates and 20% (by weight of fine aggregates) were prepared for evaluating the effect of the addition of of bitumen content of 5%, 5.5% and 6% were considered to make specimens with 100 mm diameter 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. Table 8 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 Name

AVTable 8. Volumetric Water Bulk Density VFB Binder Film Filler-Binder Properties of AsphaltVMA Mixtures Containing RCA and Glass. (%) Absorption (%) (gr/cm3 ) (%) (%) Index (µm) Ratio

Specimen

5.9 (%) 4.7 4.3 5.9 4.7 5.6 4.3 4.6 5.6 4.2 4.6 6.9 4.2 5.5 6.9 4.9 5.5 6.5 4.9 5.3 6.5 4.2 5.3

B50-G20-6

4.2

B75-G10-5 Name B75-G10-5.5 B75-G10-5 B75-G10-6 B75-G10-5.5 B75-G20-5 B75-G10-6 B75-G20-5.5 B75-G20-5 B75-G20-6 B75-G20-5.5 B50-G10-5 B75-G20-6 B50-G10-5.5 B50-G10-5 B50-G10-6 B50-G10-5.5 B50-G20-5 B50-G10-6 B50-G20-5.5 B50-G20-5 B50-G20-6 B50-G20-5.5

AV

Water 0.29 Absorption (%) 0.16 0.29 0.14 0.16 0.27 0.14 0.15 0.27 0.12 0.15 0.54 0.12 0.27 0.54 0.18 0.27 0.30 0.18 0.21 0.30 0.14 0.21 0.14

Bulk Density 2.394 (gr/cm3) 2.400 2.394 2.406 2.400 2.384 2.406 2.394 2.384 2.398 2.394 2.352 2.398 2.363 2.352 2.366 2.363 2.339 2.366 2.353 2.339 2.364 2.353 2.364

VMA 14.8 (%) 15.1 14.8 15.3 15.1 14.5 15.3 14.6 14.5 14.9 14.6 14.9 14.9 14.9 14.9 15.3 14.9 14.7 15.3 14.6 14.7 14.7 14.6 14.7

VFB 63.9 (%) 73.0 63.9 76.3 73.0 65.2 76.3 72.7 65.2 76.3 72.7 56.9 76.3 67.0 56.9 72.1 67.0 59.2 72.1 67.7 59.2 75.8 67.7 75.8

Binder Film 6.6 Index (µm) 7.7 6.6 8.2 7.7 6.6 8.2 7.4 6.6 7.9 7.4 5.9 7.9 7.0 5.9 7.7 7.0 6.0 7.7 6.9 6.0 7.7 6.9 7.7

Filler-Binder 1.1 Ratio 1.0 1.1 0.9 1.0 1.1 0.9 1.0 1.1 0.9 1.0 1.1 0.9 1.0 1.1 0.9 1.0 1.1 0.9 1.0 1.1 0.9 1.0 0.9

Height (mm) Height 68.2 (mm) 67.1 68.2 66.1 67.1 68.1 66.1 67.8 68.1 65.7 67.8 69.9 65.7 69.7 69.9 69.0 69.7 69.4 69.0 68.6 69.4 67.7 68.6 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 mixtures made with RCA glass were determined accordanceinwith Australian standards. To this asphalt mixtures madeand with RCA and glass wereindetermined accordance with Australian end and in order to compare the effect of glass addition to RCA-basalt mixtures, three specimens at standards. To this end and in order to compare the effect of glass addition to RCA-basalt mixtures, different bitumen contents of 5%, 5.5% and 6% made with 25% RCA and recycled glass at rates of 10% three specimens at different bitumen contents of 5%, 5.5% and 6% made with 25% RCA and recycled at rates 10% and 20% were density, preparedbulk anddensity, tested for density, bulk and and 20% wereglass prepared andoftested for maximum andmaximum subsequently air voids and subsequently air voids and VMA calculations. VMAdensity, calculations. same bitumen contentand andglass glass content content was forfor preparation of samples The The same bitumen content wasalso alsoconsidered considered preparation of samples containing 50% RCA. containing 50% 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 lowerofthan theInmixtures RCA without glass due to of highly hydrophobic glass. addition,containing air voids decrease with the increase bitumen content inproperty all of glass. In addition, air voids decrease with the increase of bitumen content in all samples. samples.

Figure 10. Effect of bitumen content and glass content on air voids of Mix II containing 25% RCA

Figure 10. Effect of bitumen content and glass content on air voids of Mix II containing 25% 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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Figure 11. Effect bitumencontent contentand glass content content on air of IIIIIIcontaining RCA Figure Effect ofofbitumen glass onvoids air voids voids ofMix Mix containing 50% RCA Figure 11.11. Effect of bitumen content and and glass content on air of Mix III containing 50%50% RCA without without glass and MixVIVIand andMix MixVII VIIcontaining containing 50% 50% RCA as coarse aggregate and glass as as fine without glass and Mix RCA as coarse aggregate and glass fine glass and Mix VI and Mix VII containing 50% RCA as coarse aggregate and glass as fine aggregate. aggregate. aggregate.

Importantly, theresults results volumetric analysis air calculations based bulk Importantly, thethe results of volumetric analysis andand air void calculations based on on the bulk density Importantly, ofofvolumetric analysis and air void void calculations based onthe the bulk density test and maximum density test reveal that the optimum bitumen content of asphalt testdensity and maximum testdensity reveal that optimum bitumen content of asphalt mixtures varies test and density maximum test the reveal that the optimum bitumen content of asphalt mixtures varies with theglass amount of waste glass used, so containing that mixturesmore containing more glass require with the amount of waste used, so that mixtures glass require less bitumen, mixtures varies with the amount of waste glass used, so that mixtures containing more glass require less bitumen, as presented in Figures 10 and 11. The results of the obtained optimum bitumen as less presented in Figures 10 andin11.Figures The results of 11. the The obtained optimum bitumen optimum content based on all bitumen, as presented 10 and results of the obtained bitumen content based on all specimens studied in this research work are presented in Figure 12. specimens studied research work in arethis presented Figure content based on in all this specimens studied researchin work are 12. presented in Figure 12.

Figure 12. Optimum bitumen content (OBC) of asphalt mixtures.

Figure12. 12.Optimum Optimum bitumen bitumen content (OBC) of mixtures. content (OBC) ofasphalt asphaltrequired mixtures. Furthermore,Figure as discussed previously, VMA is another parameter 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 containing 25%as and 50% RCApreviously, made with VMA recycled or without glassrequired are illustrated in Figures in Furthermore, discussed is glass another parameter to befor considered selecting optimum bitumen content. The variation of VMA with bitumen content mixtures 13 and the 14, respectively. selecting the 25% optimum bitumen content. The variation oforVMA with bitumen content for mixtures containing and 50% RCA made with recycled glass without glass are illustrated in Figures The test results on different samples showed that VMA of mixtures containing glass is quite a containing and 50% RCA made with recycled glass or without glass are illustrated in Figures 13 13 bit andlower 14,25% respectively. than the samples made with RCA without glass. It can be due to the lower air voids and and 14, respectively. The test results on different samples showed that VMA of mixtures containing glass quite a lower particle density of combined mineral aggregates in samples made with RCA andisglass. testthan results on different samples showed thatbitumen VMA Itofcontent mixtures containing glass is quite a bit bitThe lower samples made with RCA without glass. can be due to the lower air voids and However, in the all group of Mixes, VMA increases with after a minimum point.

lower than the samples with RCAmineral withoutaggregates glass. It can due tomade the lower voids and lower lower particle densitymade of combined in be samples withair RCA and glass. However, in all of Mixes, VMA increasesin with bitumen content minimum point. particle density of group combined mineral aggregates samples made with after RCAaand glass. However, 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 Figure 13. 13. Effect bitumen content glass content on VMA II containing 25% Figure Effect ofofbitumen content glass content on RCA VMA of coarse MixofII Mix containing 25% without without glass and Mix IV and Mixand V and containing 25% as aggregate and RCA glass asRCA fine 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. aggregate.

Figure 14. Effect Effectofofbitumen bitumen content glass content on VMA III containing 50% RCA Figure 14. content andand glass content on VMA of MixofIIIMix containing 50% RCA without Figure 14. Effect ofMix bitumen content and glass content on VMA of Mix III containing 50%asRCA without glass and VI and Mix VII containing 50% RCA as coarse aggregate and glass fine glass and Mix VI and Mix VII containing 50% RCA as coarse aggregate and glass as fine aggregate. without glass and Mix VI and Mix VII containing 50% RCA as coarse aggregate and glass as fine aggregate. 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% for VMA at theirwithout optimum bitumen content. However, VMA for As illustrated in (minimum) Figures 13 and mixtures glass and containing 10% glass VMA meet the requirements of 15% (minimum) for 14, VMA at their optimum bitumen content. However, for other mixtures containing 20% glass still inatthe acceptable range. requirements 15% (minimum) foris their optimum bitumen content. However, VMA for other mixturesofcontaining 20% glass isVMA still in the acceptable range. 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 Bulkconducted Density and Absorption for Asphalt Mixtures Glassthe bulk density testofwas on Water specimens containing glass and RCA towith measure Bulk density test was conducted on specimens containing glass and RCA to measure the bulk density and water test absorption of samples. Bulk density was conducted on specimens containing glass and RCA to measure the bulk density and water absorption of samples. Based on the results obtained from the bulk density test on two groups of asphalt mixtures with density andon water of samples. Based the absorption results obtained from the bulk density test on two groups of asphalt mixtures 25% and 50% in combination with different of recycled glass, it can beasphalt noticedmixtures that the on RCA the results fromwith the different bulk rates density on two groups with Based 25% and 50% RCA inobtained combination ratestest of recycled glass, itof can be noticed that bulk density decreases with the increase in the glass content due to lower bulk density of glass in with 25% and 50% RCA in combination with different rates of recycled glass, it can be noticed that the bulk density decreases with the increase in the glass content due to lower bulk density of glass comparison with basalt, as illustrated in Figures 15 and 16. thecomparison bulk density decreases with the increase in the15 glass due to lower bulk density of glass in with basalt, as illustrated in Figures andcontent 16. In addition, the basalt, data obtained from the bulk density test in comparison with as illustrated in Figures 15 and 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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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 Figure 15. Effect of bitumen content glass bulk density Mix 25% Figure Effect of Mix bitumen content and glass content content onRCA bulkas density ofaggregate Mix II II containing containing 25% RCA without15. glass and IV and Mix and V containing 25%on coarseof and glass asRCA fine without glass and Mix IV and Mix V containing 25% RCA as coarse aggregate and glass as fine without glass and Mix IV and Mix V containing 25% RCA as coarse aggregate and glass as fine aggregate. aggregate. 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 Figure 16. Effect bitumen content glass on density III 50%Figure RCA Figure 16. Effect ofwater bitumen content and andbecause glass content content on bulk bulk density of of Mix Mix III containing containing 50% RCA 17 appear to have lowof absorption of the hydrophobic property of glass. Figure 16. Effect of Mix bitumen content and glass content on RCA bulk density of Mix III containing 50% RCA without glass and VI and Mix VII containing 50% as coarse aggregate and glass as fine without glass and Mix VI and Mix VII containing 50% RCA as coarse aggregate and glass as fine aggregate. illustrates the water absorption of all different specimens. without glass and Mix VI and Mix VII containing 50% RCA as coarse aggregate and glass as fine aggregate. aggregate.

In addition, the data obtained from the bulk density test indicate that water absorption In addition, the data obtained from the bulkglass, density indicate that water absorption decreases with respect to the amount of recycled andtest asphalt mixtures containing glass 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 appear to have low water absorption because of the hydrophobic property of glass. Figure 17 illustrates the water absorption of all different specimens. illustrates the water absorption of all different specimens.

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

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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4.4.3. Determination of Voids Filled with Bitumen (VFB) for Asphalt Mixtures with Glass

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4.4.3. Determination of Voids Filled with Bitumen (VFB) for Asphalt Mixtures with Glass 4.4.3. Determination Voids Filled Bitumen (VFB)with for Asphalt Mixturescontent with Glass Figures 18 and 19 of illustrate the with variation of VFB the bitumen and glass content. Figures 18 and 19 illustrate the variation of VFB with the bitumen content and glass content. Figures 18 and 19 illustrate the variation of VFB with the bitumen content and glass content. As previously stated, VFB is one of the indicators of asphalt mixture performance in terms of durability, As previously stated, VFB is one of the indicators of asphalt mixture performance in terms of As previously stated, VFB is one of the indicators of asphalt mixture performance in terms of fatigue resistance and resistance susceptibility to rutting. to rutting. durability, fatigue and susceptibility durability, fatigue resistance and susceptibility to rutting.

Figure 18. Effect of bitumen content and glass content on VFB of Mix II containing 25% RCA without Figure 18. Effect of bitumen content and glass content on VFBofof Mix containing II containing 25% RCA without Figure 18. Mix Effect bitumen and25% glassRCA content on VFB Mix IIand RCA without glass and IVof and Mix V content containing as coarse aggregate glass as 25% fine aggregate. glassglass and and MixMix IV and Mix VV containing as coarse coarseaggregate aggregate and glass as fine aggregate. IV and Mix containing25% 25% RCA RCA as and glass as fine aggregate.

Figure 19. Effect of bitumen content and glass content on VFB of Mix III containing 50% RCA Figure 19. Effect ofMix bitumen glass content on VFB of Mix III containing 50%asRCA without glass VIcontent andcontent Mixand VIIand containing 50% as and50% glass Figure 19. Effect ofand bitumen glass content onRCA VFB of coarse Mix IIIaggregate containing RCAfine without 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. aggregate.

As can be observed in Figures 18 and 19, the values obtained for asphalt mixtures made with

As can be observed Figures 18and and 19, 19, obtained forglass asphalt with As can beRCA observed in in Figures the values values obtained for asphalt made glass and are higher than the18 samples containing RCA without due mixtures to amixtures lowermade degree of with glass and RCA are higher than the samples containing RCA without glass due to a lower degree of glassabsorption and RCA resulting are higher than the effective samplesbinder. containing RCA without glass due to a lower degree of in increased absorption resulting in increased effectivebinder. binder. absorption resulting in increased effective 4.4.4. Determination of Binder Film Index (BFI) for Asphalt Mixtures with Glass

Determination Binder of Binder FilmIndex Index (BFI) for Mixtures with Glass 4.4.4.4.4.4. Determination Film for Asphalt Asphalt Mixtures with Glass As discussedofpreviously, BFI is an (BFI) indicator of adequate cohesion and the incorporation of

As discussed BFI is an indicator of adequate cohesion and the incorporation of sufficient binderpreviously, inpreviously, the asphalt mixture. As discussed BFI is an indicator of adequate cohesion and the incorporation of sufficient binder in the asphalt mixture. According to the resultsmixture. obtained, the binder film index of different mixtures were investigated sufficientAccording binder in to the asphalt thethe results obtained, thewith binder film index of different were investigated in this research and variation of BFI glass and bitumen contentmixtures in two groups of samples According to the results obtained, thewith binder film index of different mixtures were investigated in this research and the variation of BFI glass and bitumen content in two groups of samples containing 25% and 50% RCA are illustrated in Figures 20 and 21. in this research25% andand the50% variation BFI withinglass and containing RCA areofillustrated Figures 20bitumen and 21. content in two groups of samples

containing 25% and 50% RCA are illustrated in Figures 20 and 21.

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Figure 20. Effect of bitumen contentand andglass glasscontent content on BFI ofofMix II II containing 25%25% RCA without Figure 20. Effect of bitumen content onBFI BFIof Mix containing without Figure 20.Mix Effect bitumen and25% glass content on Mix IIand containing RCARCA without glass and IVof and Mix V content containing RCA as coarse aggregate glass as 25% fine aggregate. glassglass and Mix IV and MixMix V containing coarseaggregate aggregate and glass as fine aggregate. and Mix IV and V containing25% 25%RCA RCA as as coarse and glass as fine 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

glass MixofVIbitumen and Mix content VII containing 50% content RCA as coarse and glass as fine aggregate. Figure 21. and Effect and glass on BFIaggregate 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. 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 As film can be observed in samples Figures 20 and 21,glass. both However, samples containing glass have slightlyathigher binder thickness than without the comparison of samples their binder film thickness than samples without glass. However, the comparison of samples at their As can bebitumen observed in Figures andBFI 21,for both samples containing higher optimum content shows20that samples containing 20% glass glass have is lessslightly than the optimum bitumen content shows that BFI for samples containing 20% glass is less than the binder film thickness than samples without glass. However, the comparison of samples at their minimum requirements of 7.5 microns. minimum requirements of 7.5 microns. optimum bitumen content shows that BFI for samples containing 20% glass is less than the minimum

4.5. Volumetric of Asphalt Mixtures at Optimum Bitumen Content requirements of 7.5Analysis microns.

4.5. Volumetric Analysis of Asphalt Mixtures at Optimum Bitumen Content The results of volumetric properties evaluation of asphalt mixtures with different The results ofof Asphalt volumetric properties evaluation of Content asphalt mixtures with indifferent 4.5. Volumetric Analysis Mixtures at Optimum Bitumen combinations of aggregates at their optimum content are presented in Table 9. As shown Table 9, combinations of aggregates at their optimum content are presented in Table 9. As shown instandard Table 9, the results of the tests on asphalt mixtures reveal that all mixtures made of RCA meet the The resultsofofthe volumetric properties evaluation of asphalt mixtures with different combinations the results testsproperties. on asphalt However, mixtures reveal that all mixtures made ofnecessitates RCA meet the limits for volumetric their high bitumen absorption thestandard study of of aggregates at their optimum content are presented in Table 9. As shown in Table 9, the of results limits for volumetric properties. However, their high bitumen absorption necessitates the study volumetric properties of asphalt mixtures made with RCA in combination with recycled glass. To of thevolumetric tests on asphalt mixtures reveal that all mixtures made of RCA meet standard limits properties of asphalt with RCA in combination withthe recycled To for this point, as can be observed inmixtures Table 9, made all asphalt mixtures containing RCA and 10% glass. recycled volumetric properties. their high necessitates theand study volumetric this canAustralian beHowever, observed in Table 9, bitumen all asphaltabsorption mixtures containing RCA 10%of recycled glasspoint, meetasthe Standards’ requirements and therefore are deemed appropriate for glass meet the Australian Standards’ requirements and therefore are deemed appropriate forpoint, properties of asphalt mixtures made with RCA in combination with recycled glass. To this consideration as asphalt mix design. In addition, results for samples with RCA and 50% of recycled consideration asphalt design. In addition, results for RCA and 50%9),of recycled as can be observed Tablemix 9, all asphalt mixtures containing RCA with and 10% glass meet glass, except as forin binder film index and VMA (which aresamples shown in bold inrecycled Table meet the the glass, except for binder film index and VMA (which are shown in bold in Table 9), meet the Australian Standards’ requirements andVMA therefore are deemed forAustralian consideration as asphalt standard typical values. However, for these samples appropriate are within the Standards standard values. However, VMAthat for asphalt these samples are within the Australian Standards limits. To this point, itresults can be for concluded containing 25% RCA and 10%for glass mix design. Intypical addition, samples with RCAmixtures and 50% of recycled glass, except binder limits. To thiscomparable point, it can be concluded that asphalt mixtures containing 25% RCA and 10% glass are the most mixtures with control samples. film index and VMA (which are shown in bold in Table 9), 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.

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

Optimum Bitumen Content (%)

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Bulk Density (gr/cm3 )

VMA (%)

VFB (%)

Binder Film Index (µm)

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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-G20 5.3Bitumen 2.390 14.5 69.5Binder Film 7.1 Filler-Binder 1.0 Optimum Bulk Density VMA (%) Specimen 3) B50 Name 6.2 (%) 2.368 15.9 VFB (%) 72.2Index (µm) 8.2 Ratio 0.9 Content (gr/cm B50-G10 5.9 2.365 70.8 7.6 B100 5.1 2.442 15.5 15.2 71.5 7.8 1.1 0.9 B50-G20 5.6 2.355 69.5 7.1 B75 5.8 2.411 15.6 14.6 72.0 7.9 0.9 1.0 Standard Limit B75-G10 5.4 2.39815.013–20% 70.5 60–80% 7.5 1.0 0.8–1.2 Typical Value 15% (min)69.5 B75-G20 5.3 2.39014.5 7.17.5 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 B50-G20 5.6 2.355rates of bitumen 14.6 69.5 7.1 1.0 In addition, for all samples at different content, as presented in Tables 7 and 8, Standard Limit 13–20% 60–80% 0.8–1.2 can be observed that increasing the bitumen content results in the specimen height reduction. Typical Value 15% (min) 7.5 µm (min) -

it This effect can be due to the extra lubrication provided by the hot bitumen during compaction leading to the better and quicker for the same compactive effort.as presented in Tables 7 and 8, In addition, for allcompaction samples at different rates of bitumen content, it can be observed that increasing the bitumen content results in the specimen height reduction.

4.6. Resilient Modulus Asphalt at Optimum Bitumen This effect can beofdue to theMixtures extra lubrication provided byContent the hot bitumen during compaction

leading to thewell betterestablished and quickerthat compaction for the same compactive of effort. It has been predicting the performance 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 It materials has been well establishedasthat predicting the performance in terms of combinations well as the materials 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 different resilientmixtures modulus through the indirect tensile test for three specimens selected based on the in terms of materials combinations as well as the materials amount. results of Based primary tests, as presented in Tabletests, 10. the most acceptable samples were selected for on the result of the primary estimating their resilient modulus through the indirect tensile test for three specimens selected 10. Material combination for preparation of specimens of indirect tensile test. based onTable the results of primary tests, as presented in Table 10. Aggregate (%) Fine Aggregate of (%) Table 10. MaterialCoarse combination for preparation of specimens Indirect Tensile Test. Optimum Bitumen Asphalt Mixture Content (OBC, %) Basalt RCA Basalt Glass Coarse Aggregate (%) Fine Aggregate (%) Asphalt Mixture Optimum Bitumen Content (OBC, %) B100 Basalt 100 0 100 0 5.1 RCA Basalt Glass B75 75 25 100 0 5.8 B100 100 0 100 0 5.1 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 To conduct the resilient modulus test, a triaxial repeated loading machine capable of applying 50 kPa of loading was used considering repeated haversine loading. Using this machine, 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 computer (Figure 22). (Figure 22). desktop computer

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 Mixture

Ave. Sample Height (mm)

Ave. Sample Diameter (mm)

Peak Load (N)

Recovered Horizontal Strain (µε)

Mr (MPa)

B100 B75 B75-G10

64.95 68.225 68.025

99.925 99.95 99.975

2718.7 3252.7 3302.6

50.01 51.52 49.08

5613 6205 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)

(2)

(3)

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. 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. 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

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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 Table 8, 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 Table 9, 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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