Sustainable asphalt concrete containing high reclaimed asphalt pavements and recycling agents: Performance assessment, cost analysis, and environmental impact

Journal Pre-proof Sustainable asphalt concrete containing high reclaimed asphalt pavements and recycling agents: performance assessment, cost analysis, and environmental impact

Hamid Jahanbakhsh, Mohammad M. Karimi, Hamed Naseri, Fereidoon Moghadas Nejad PII:

S0959-6526(19)33707-2

DOI:

https://doi.org/10.1016/j.jclepro.2019.118837

Reference:

JCLP 118837

To appear in:

Journal of Cleaner Production

Received Date:

23 June 2019

Accepted Date:

10 October 2019

Please cite this article as: Hamid Jahanbakhsh, Mohammad M. Karimi, Hamed Naseri, Fereidoon Moghadas Nejad, Sustainable asphalt concrete containing high reclaimed asphalt pavements and recycling agents: performance assessment, cost analysis, and environmental impact, Journal of Cleaner Production (2019), https://doi.org/10.1016/j.jclepro.2019.118837

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Sustainable asphalt concrete containing high reclaimed asphalt pavements and recycling agents: performance assessment, cost analysis, and environmental impact Hamid Jahanbakhsh1, 2, Mohammad M. Karimi3, Hamed Naseri2, Fereidoon Moghadas Nejad2 1 Department

of Civil Engineering, University of Science and Culture, Tehran, Iran. Department of Civil & Environmental Engineering, Amirkabir University of Technology (Tehran Polytechnic), Iran. 3 Department of Civil and Environmental Engineering, Tarbiat Modares University, Tehran, Iran. 2

Abstract In this study, mechanical performance, environmental impacts, and economic benefit criteria are considered so as to introduce sustainable asphalt mixtures containing a high content of reclaimed asphalt pavements. The low-temperature cracking, moisture susceptibility, fatigue cracking, and rutting resistance of asphalt concrete are the most common deficiencies of rejuvenated reclaimed asphalt mixtures. Therefore, to analyze the mechanical characteristics, different experimental tests including Marshall Stability, indirect tensile strength, tensile strength ratio, semi-circular bending (at low and intermediate temperatures) are applied, and their results are taken into consideration as determinate mechanical performances in optimizing the mixture. The percentage of landfill embedment, saving in energy consumption, and the amounts of harmful emissions are utilized to compare the environmental influences of eco-friendly and the virgin mixtures. Drawing the results of experimental tests and statistical analysis (i.e., ANOVA, and Tukey pairwise comparison), the mechanical characteristics of mixtures containing various content of reclaimed asphalt pavements (i.e., 30%, 60%, and 100%), waste engine oil, and supplementary binder modified with crumbrubber simultaneously are better than or equal to that of the conventional mixture. The environmental analysis reveals that the refined mixture is by far valuable than the virgin mixture. The proposed asphalt concrete incorporating the 100% of reclaimed asphalt pavements significantly reduces the pollution generated by the production and preparation of materials to manufacture asphalt mixture. Moreover, the energy consumed to manufacture, the percentage of landfill embedment, and the rate of economic conservation considerably decrease in suggested asphalt concretes containing different content of reclaimed asphalt pavements in comparison with the virgin mixture. This environmental Protection of the examined asphalt concretes enhances as the content of reclaimed asphalt pavements increases.

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Corresponding author: Hamid Jahanbakhsh, Department of Civil & Environmental Engineering,

Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran, Email: [email protected].

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Keywords Reclaimed asphalt pavements (RAP), Crumb-rubber (CRM) binder, Waste engine oil (WEO), Mechanical characteristics, Environmental impact, Cost analysis.

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1. Introduction In recent years, the necessity of reusing industrial waste materials in pavement preservation, maintenance, and reconstruction is widely assessed to achieve sustainable solutions. Billions of tonnes of waste materials annually have being produced around the world, and they can be recycled and reused in pavement applications leading the environment to protect by reducing the accumulation of landfills, saving raw materials extracted from the environment, and consuming fewer amounts of energy in mixing process and transportation of virgin materials (Chen and Wang, 2018). Approximately 30% of global air pollution and a fourth of fossil fuel consumption around the world are pertinent to transportation sector (Mallick and Veeraragavan, 2010), and more than 7% of these contents is the contribution of pavement industry (Piantanakulchai et al., 1999). The influences of industrial by-products and waste landfills have been extensively studied in several surveys, and it is comprehended that these refined materials can be suitably replaced as the raw materials in both concrete and asphalt pavements. Furthermore, taking the optimal content of replacement into account, the long-term performance of pavements would be considerably improved (Leng et al., 2018; Phummiphan et al., 2018). Reclaimed asphalt pavement (RAP) is a mixture, including aged asphalt binder and aggregates produced by recycling hot mix asphalt (HMA) known as the most common recycled materials used in flexible pavements. RAP as a less-costly binder can be replaced with the high-priced original binder to prepare eco-friendly pavements (Abraham and Ransinchung, 2018; Zhang and Muhunthan, 2017). Moreover, Using aged asphalt bitumen in new mixtures leads to reduce the content of required new bitumen. Hence, utilizing RAP in HMA mixtures is economically appealing (Noferini et al., 2017). Besides, using RAP as waste material in pavement structure decrease the emission of greenhouse gas into the atmosphere leading to improvement in the environment health (Chen and Wang, 2018; Xiao et al., 2019). The availability of RAP in Italy, Germany, France, and The Netherlands are equal to 10, 11.5, 6.9, and 4.5 million tonnes, respectively, and it is plausible decision to reuse these landfills as valuable materials in green pavement applications (Noferini et al., 2017). As reported by pavement engineers, in 2015, 74.2 million tonnes of RAP has been used in pavement construction in the United States (Hansen and Copeland 2015). In the 1970s, owing to the increment of crude oil price, federal highway administration (FHWA) provided funding for the State transportation departments to scrutinize the characteristics of recycled asphalt and to construct paving projects. Consequently, recycling asphalt pavements became well-recognized, and it has been used in many projects (Copeland 2011). However, it is worth mention that the very often states did not allow the using of RAP more than 25 percent in the surface layer which selected through the adverse effects of the high content of RAP on the long term performance of asphalt concrete (Salman et al., 2017). In addition to land use reduction, economic and environmental advantages, the mechanical characteristics and long term performance of asphalt concrete fabricated with RAP has attracted growing attention. The previous researches stated that the asphalt layer incorporating the small amounts of RAP (less than 30 %) similarly performed to those asphalt mixture constructed with 3

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virgin materials (Mogawer et al., 2011; McDaniel et al., 2000). In this regards, it has been indicated that, in case of low content of RAP, adding reclaimed asphalt leads to increasing the fatigue cracking resistance (Leng et al., 2018), increasing rutting resistance (Leng et al., 2018), enhancing moisture damage potential of the mixes, increasing tensile strength ratio (Singh et al., 2017), and reducing the variability of binder properties and binder content by a similar magnitude during mixing and milling (Zaumanis et al., 2018). On the flip side, Li et al. (2008) investigated the appropriate content of RAP in the low percentage of RAP asphalt mixtures. Three different rates of replacement, including 0%, 20%, and 40% were taken into account, and various specimens were assessed based on dynamic modulus testing and semi-circular bend fracture testing. The results of this study revealed that the dynamic modulus values of RAP mixtures were higher than that of control mixtures. Nonetheless, control mixtures had the highest fracture energy, and by increasing the percentage of RAP, the fracture energy was reduced (Li et al., 2008). Furthermore, Shu et al. (2010) expressed that by addition of RAP to asphalt mixtures, semi-circular bending tensile strength is increased. Nevertheless, the post-failure tenacity of mixtures is by far reduced (Shu et al., 2010). As a matter of fact, the amount of generating RAP is much more than the volume that is using in pavement applications. According to the report of the European Asphalt Pavement Association (EAPA), despite abundant availability of RAP around the world, merely 47% of existing RAP has been used in pavement applications in 19 developed countries (Zaumanis et al., 2014a; EAPA, 2012). A comprehensive look at the previous investigations reveals that RAP usually has been replaced with less than 50% of virgin materials. Nevertheless, this ratio can be increased if the performance of the pavement is not deteriorated. Concerning the performance of asphalt concrete materials incorporating high content of RAP, it has been shown that these mixtures had higher rutting resistance, and resilient modulus (Li et al., 2018). However, the national cooperative highway research program (NCHRP) project revealed that the addition of high RAP affects the volumetric properties of prepared asphalt concrete which can cause negative influences on the mechanical characteristics of asphalt mixture (West et al., 2013; Zhang et al., 2016). Moreover, it has been argued that the high percentage of RAP reduces fatigue resistance (McDaniel et al., 2000; Al-Qadi et al., 2012) and thermal cracking resistance of asphalt concrete (McDaniel et al., 2000; Islam et al., 2014). Besides, the observations of the Kansas department of transportation indicated that the high Rap results the premature cracking of asphalt concrete (Sabahfar et al., 2016). This outcome can be related to lower fracture resistance of asphalt concrete containing a high percentage of RAP (West et al., 2013). Based on the aforementioned concepts, it can be disclosed that there is need to provide proper producing process, fabricating samples at the appropriate temperature, adding optimal amounts of apposite admixtures to produce the asphalt mixtures with 100% RAP which possess mechanical and rheological performance as analogous to virgin material pavements (Zaumanis et al., 2014a; Yu et al., 2017; Cavalli et al., 2017). As stated previously, in the absence of special additives and incorporation of high RAP content, the cracking performance is undermined, the stiffness of the mixtures is increased due to the aged 4

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binder of the RAP, and compactibility of asphalt is weakened. Ergo, higher stiffness of high content RAP mixtures leads to reduce the workability and to be more prone to low-temperature cracking (Riccardi et al., 2017; Safi et al., 2018; Majidifard et al., 2019). In order to compensate for these deficiencies, several methods have been analyzed, and some feasible solutions have been introduced. One of the conventional techniques to improve compactibility is to utilize RAP with warm-mix asphalt (WMA) technology. Using RAP and warm-mix additive simultaneously improves the compactibility of the mixtures (El Sharkawy et al., 2017). To improve the lowtemperature characteristics and to drop the stiffness of aged binders, rejuvenators are fundamentally added to the mixes. Rejuvenators spread into the binders, and their properties (e.g., relaxation and thermal stress releasing) are improved. The task of rejuvenators is to revive the equivalence between asphaltenes and maltenes by adding more maltenes and enhancing the dispersion of asphaltenes within the maltenes matrix (Elkashef et al., 2018a, 2018b). Hence, by using rejuvenators, the materials are suitably softened, and it probably leads to avoiding thermal cracking and brittleness. Furthermore, the durability, resistance to permanent deformations (Bonicelli et al., 2017), cracking (Xie et al., 2017), and moisture resistance are enhanced (Song et al., 2018). Several kinds of rejuvenators and various methods for mixing asphalt concretes containing RAP have been widely evaluated to measure mechanical and long-term performances. The two-drum mixing method is a valuable technique to produce rejuvenated RAP mixtures since it decreases air voids substantially. Besides, it boosts the tensile strength, moisture damage resistance, rutting resistance, and low-temperature cracking resistance (Shao et al., 2017). Using Storflux Nature and Rheofalt as rejuvenators in high content RAP mixtures improves fatigue behavior, enhances lowtemperature properties, and increase the permanent deformation resistance (Büchler et al., 2018). Likewise, soybean oil softens the RAP binders, enhances low-temperature properties, and improves fatigue resistance (Elkashef et al., 2018a, 2018b). Although commercial rejuvenators and bio-based oils are fruitful, their susceptibility to aging is high because some of them contain volatile ingredients in their chemical structure. Nonetheless, the percentage of volatile components in waste cooking oil (WCO) and waste engine oil (WEO) is by far less than that of fresh bio-oils because WCO and WEO tolerate under the high temperature during the production process. That is to say, waste oils are highly qualified for application in hot mixing asphalt process because of their stability at temperatures above 220 ºC (Majidifard et al., 2019). Among all the utilized rejuvenators, waste engine oil has attracted growing attention regarding the similar molecular structure, physical and chemical properties of WEO with petroleum asphalt (Liu et al. 2018). The partial utilization of enhanced asphalt binder performance (Bennert et al. 2016), making asphalt binder with more flexibility (Qurashi et al. 2018), environmental-friendly (Liu et al. 2018), and economic benefits (Jia et al. 2014) have been introduced as the most significant merits of WEO. Furthermore, it has been postulated that the leading chemical composites of WEO are aromatics which are similar to the aromatics of asphalt binder (Liu et al. 2018). Therefore, WEO, as a rejuvenator, can effectively be replaced with the light components (i.e., aromatics) of 5

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asphalt binder, which had become asphaltene during the aging process. On the other hand, WEO is harmful material for the environment because of its disposing into streams and landfill (Dinh et al., 2018). In recent years, approximately the annual consumption of engine oil is 400 million liters that is pernicious and destructive in case of leaving it exposed in the environment. However, the U.S. Department of Energy indicated that the majority of waste engine oil utilizes as fuel, this process can create air pollutions which deteriorate the environment through the burning of waste oil (U.S.D.O. Energy). Thus, taking environmental consequences, WEO is more viable so as to be used as a rejuvenator in asphalt concrete containing high RAP (Dinh et al., 2018). The most critical drawback of rejuvenators is to reduce the rutting resistance of pavements since rejuvenator decreases the viscosity causing to increase viscoelastic-viscoplastic strain. However, rejuvenators decrease the stiffness of the aged binder, leading change the hardened RAP binder to soft; they cannot recover all the rheological and mechanical properties of stiff binders. Therefore, in order to decompensate for this deficiency, adding crumb-rubber (CRM) as commonly used environmental friendly additive to rejuvenated RAP is an environmentally friendly solution (Majidifard et al., 2019). Initially, generating crumb-rubber by mixing bitumen and natural rubber took place in the 1840s (Bressi et al., 2019), it was used in projects for the first time in the 1930s (Yildirim, 2007). In this regards, it was postulated that the crumb-rubber could use in conjunction with rejuvenating agents through its ability to enhance the properties of the asphalt binders and mixtures (Mogawer, 2013). The automobile and vehicle industry has been wildly producing waste tires around the world, and this trend is being accelerated drastically. More than 4 million tonnes of crumb tires were generated in the United States (USA) in 2017 (U.S. Scrap Tire Manufacturers Association, 2018). Therefore, recycling and reusing waste tires should be taken into consideration more seriously since stocked pile tires are pertinent landfills which influence the green environment and threaten the living organism’s life. By accumulating waste tires, favorable environments for mosquitoes are provided to reproduce. Mosquitoes can pass dangerous diseases, including dengue fever and encephalitis. Moreover, Aedes mosquitos transfer Zika virus in tropical zones. On the flip side, soil and underground water can be contaminated, and the massive volume of the greenhouse can be emitted to the atmosphere when waste tires are burned in the environment. Accordingly, to the aforementioned advantages of using CRM in asphalt concrete and disadvantages of leaving them in the environment, recycling waste tires, admittedly, attracts considerable attention, and using crumb-rubbers in the pavement can provide the desirable mechanical properties for asphalt concrete and prevent disastrous consequences of waste tires (Fakhri and Azami, 2017; Wang et al., 2018). The emissions of carbon monoxide (CO) and methane (CH4) in rubberized asphalt mixtures are much lower than hot mix asphalt, and rubberized asphalt technology is known as a green technology because of energy saving, human health, minimizing resources depletion, protecting ecosystems, reduction in greenhouse gas emissions, and decreasing the noise level of the pavement (Wang et al., 2018; Farina et al., 2017). To compensate for the stiffening effect of RAP in mixtures, using softer binders is a commonly used technique. However, the modification of softer binder by CRM provides more efficient and environmental-friendly solutions to overcome this problem 6

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(Kocak et al., 2017). Huang et al. (2002) analyzed the performance of crumb-rubber asphalt pavement, and they were compared with that of conventional asphalt mixture. The outcome of this analysis implied that the conventional asphalt mixture outweighed the crumb-rubber asphalt pavement based on laboratory strength characteristics. However, the crumb-rubber asphalt mixtures prevailed the conventional asphalt mixture according to international roughness index numbers, fatigue cracks, and rut depth after 5 to 7 years of traffic (Huang et al., 2002). Mull et al. (2002) declared that the fracture resistance of asphalt specimens is improved by the addition of crumb-rubber to the mixture proportion (Mull et al., 2002). Furthermore, crumb-rubber plays a decisive role in reducing temperature susceptibility and stiffness, improving the moisture resistance and low-temperature cracking behavior, increasing the fatigue resistance of asphalt concrete (Kocak et al., 2017; Fakhri and Azami, 2017; Majidifard et al., 2019). Regarding the increasing price of asphalt binder through the gasoline costs growing, lowering the price of asphalt pavements via utilizing high percentages of reclaimed asphalt pavements brings about immense concerns. However, as previously discussed the aged binder of the RAP can cause lower workability, premature cracking under various environmental conditions and traffic loadings, the increment of mixture stiffness, fatigue damage, and low temperature cracking. In order to compensate for these deficiencies, the use of a new softer binder or rejuvenating additives employs by crumb-rubber modification can be a viable and powerful method to use high percentages of RAP. Based on the aforementioned concepts, the main contribution of this research is to propose recycling asphalt mixtures containing high percentages of RAP (up to 100%) with different additives which have a similar rheological and mechanical performance with the virgin mixture. To this end, mechanical tests, such as Marshall Stability test, indirect tensile strength (IDT) test, semi-circular bending (SCB) test at low and intermediate temperatures, and tensile strength ratio test, have been conducted to assess the performance of various asphalt mixture. The statistical analyses have been performed to objectively investigate the mechanical performance of asphalt mixture containing the high content of rejuvenated RAP accompanied by CRM in asphalt concrete. Furthermore, the environmental impacts and economic benefits of fabricated asphalt mixture have been analyzed and compared with the virgin mixture. 2. Materials, sample preparation, and mix design In this research, the reclaimed asphalt pavements were milled from the in-situ which produced by pen 60/70 (PG64-22) asphalt binder and nominal maximum aggregate size 19 mm. The obtained RAP from the field had a nominal maximum aggregate size of 12.5 mm through the aggregate crushing during the milling process. The asphalt binder of the RAP was extracted through the trichloroethylene solvent and recovered utilizing the rotary evaporator. The extraction results revealed that the examined RAP had 5.64% asphalt binder. Based on the concepts as stated earlier, in this study, the binder which its penetration grade is 60/70 (PG64-22) was selected as the base binder. Siliceous aggregate with a nominal maximum aggregate size (NMAS) of 12.5 mm was used as the virgin aggregate, and its grading curve is depicted in Fig. 1 conforming the necessities of ASTM D3515-01 specification. In some 7

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specimens, different amounts of RAP are replaced with the virgin aggregate. Three different contents of replacement, including 30%, 60%, and 100% RAP are taken into consideration so as to compare their performance and environmental effects with those of the virgin mixture. Insert Fig. 1. As stated in the previous section, the utilizing high percentage of RAP in the asphalt concrete facing challenges containing the occurrence of premature cracking and changes of volumetric properties. Ergo, in order to the recommendation regarding the design of the green asphalt mixture containing high RAP as the dominant objective of this research using the rejuvenator or softening agent should be of concern. Since waste engine oil in addition to Environmental hazards has similar physical and chemical properties with asphalt binder and has the capability to mix with RAP, WEO was used as a rejuvenator in this study. On the subject of the WEO capability concerning to recover the characteristics of RAP binder through the aging, Zaumanis et al. (2014b) demonstrated that WEO as a rejuvenator could enhance the performance grade of the aged asphalt binders of RAP, however, WEO was not able to improve it to the level of the virgin binder. This can cause the workability problem of the rejuvenated asphalt concrete (Zaumanis et al., 2014b) and therefore results to alter the volumetric properties (West et al., 2013; Zhang et al., 2016). This observation was also presented in the findings of GDOT, which indicated that the rejuvenators could not diffuse and enhance the properties of the whole asphalt binder in the RAP (GDOT 2013). To overcome this issue, the mix design was conducted for each examined mixtures in this research. According to previous studies and suggestion was made by NCHRP 452, using softer binder (i.e., one hightemperature grade softer than RAP binder) leads the deficiencies of RAP to retrieve (McDaniel et al., 2000). Accordingly, Pen 85/100 (PG58-22) was selected as a supplementary binder for all specimens containing RAP. The specifications of the binders used in this research are presented in Table 1. Furthermore, due to improving the prepared asphalt mixtures resistance against cracking in this research, supplementary softer binder modified with crumb-rubber was assessed. Taking the previous studies, the optimal content of crumb-rubber is 10% of the binder weight (Geckil et al., 2108; Jahanbakhsh et al., 2016). Hence, when CRM is added to the samples, it is replaced with 10% of the weight of the supplementary binder. In this investigation, sulfur is utilized as the crosslinking agent to boost the adhesion between the crumb-rubber and binder, leading to eliminate the storage stability problem of CRM modified binder. Thus, 0.1% of total binder weight is considered as the amount of sulfur, and it is added to the crumb-rubber before the mixing process. In order to fabricate the modified asphalt binder, asphalt binder is heated to 160°C. Afterward, crumb rubber is added to the mixture gradually. Then, the mixture is mixed through the shear rate of 5000 rpm for an hour. In order to conduct the mix design for studied asphalt concretes, the optimum amount of binder was elaborated regarding the marshal stability results and volumetric properties. Marshal mix design method is applied, and 5.05, 5.4, 5.8 and 6.3% (wt% of asphalt mixture containing 8

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aggregate, binder, and rejuvenator) is allocated to binder content to yield the target air voids content of 4% for virgin, 30%, 60%, and 100% RAP mixtures, respectively. All the fabricated mixtures mixed and compacted at 151 ºC and 136 ºC, respectively, through the viscosity results of the virgin binder. Then, in order to prepare the asphalt mixture containing RAP, the RAP and rejuvenator mingled and heated at mixing temperature for two hours. All the mixture after mixing were placed at compaction temperature for four hours resembling the short term aging during the mixture production in the asphalt plant. Insert Table 1. 3. Optimum rejuvenator content According to explanations mentioned in the introduction, the oxidative aging occurred during the service life of pavements causing to lose the volatile compounds of bitumen. This process results in increasing the binder viscosity and make the asphalt binder more brittle and more prone to cracking and other deteriorations that have adverse effects on durability. In order to diminish the aging effect of RAP binders on the asphalt mixture properties, the softer supplementary binder, rejuvenators, modifiers, and combination of these modifiers need to be assessed. It has been indicated that the addition of rejuvenator or softening agent as a commonly used solution reduces the stiffness of the existing aged binder in RAP. Ergo, based on the environmental and mechanical advantages of waste engine oil, the WEO was selected as a rejuvenator in this research. In order to investigate the effects of WEO on the properties of RAP binder, the penetration, softening point, and ductility tests were conducted on the recovered asphalt binder with 2 to 12% (wt% of binder) WEO with an increment of 2%. The recovered asphalt binder was heated up to 140 ºC; then, the required amount of WEO was added to the binder. The prepared binder was kept at 140 ºC for six hours, ensuring the diffusion of WEO into the aged bitumen. The results of the penetration, softening point, and ductility tests for different aged and rejuvenated asphalt binders are shown in Fig.2. As depicted in Fig.2, the addition of WEO into the RAP binder leads to increasing in penetration and ductility and decreasing the softening point. This trend keeps continued as WEO content increases. It can be inferred that the 10% of WEO can enhance the penetration of aged asphalt close to the virgin binder. As pointed out in Fig.2, the penetration and ductility of aged binder significantly increase as WEO increases and changes are more substantial at higher content of WEO. However, the softening point of RAP binder considerably decreases as WEO increases at lower contents. Ergo, the penetration and ductility changes of aged binder follow the positive exponential function. However, the decrease in softening point showed a negative exponential manner. The final fitted functions for different test methods are illustrated in Fig.2. Regarding the aging of the high-temperature production of asphalt concrete as well as higher cost and energy consumption, there is a need to lower the stiffness of asphalt binder through the rejuvenator additive. The rejuvenator should remarkably decrease the viscosity of aged asphalt 9

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binder, ensuring enough fluidity of asphalt binder so as to coat the aggregates. Thus, the rotational viscosity of the studied binders was obtained over a temperature range of 95 to 165 ºC with an increment of 5 ºC. The results of a rotational viscometer (RV) test of aged and rejuvenated binders are shown in Fig. 3. Insert Fig. 2. Based on the results depicted in Fig.3, it can be concluded that WEO as a rejuvenator can accordingly enhance the viscosity of aged asphalt binder so as to fabricate of asphalt mixture containing a high percentage of RAP. As illustrated in Fig.3, WEO lowered the viscosity of aged binder to 3000 mPas at 135 ºC, which meets the Superpave requirement. Furthermore, it can be demonstrated that 10 to 12% (wt% RAP binder) addition of WEO can decrease the viscosity of aged binder close to the viscosity of virgin binder. In addition, in order to investigate the effect of WEO on the characteristics of aged asphalt binder, the penetration viscosity number (PVN) of different asphalt binders were calculated through the results of penetration test at 25 ºC and viscosity at 135 ºC. The resultant PVN number is depicted in Fig. 4. As can be inferred from Fig. 4, the addition of WEO decreases the PVN number of aged binder, and this trend extends as WEO content increases. It should be worth mentioning that the aged binder rejuvenated with 10% WEO has higher PVN number compared to a virgin binder indicating the positive impact of WEO on the temperature susceptibility of aged asphalt binder. Insert Figs. 3 and 4. This section aimed to find the optimum content of WEO as a rejuvenator to recover the rheological properties of aged asphalt binder. Several research studies have been showed that the excess amount of rejuvenator causes the stripping of the binder (Zaumanis et al. 2013), negative impact on the rheological properties (Kaseer et al. 2017), and poor performance of prepared asphalt mixture (Hesp and Shurvell 2010). In this regards, Zaumanis has been argued that the percentage of rejuvenator which can recover the penetration of aged asphalt binder, moreover, can satisfy the SHRP requirements considered as an optimum content of rejuvenator. To this end and through the results of this section, the 10% of WEO, which can resolve the penetration of aged binder and improve the temperature susceptibility of asphalt binder, has been selected as optimum rejuvenator content. 4. Experimental results and discussion In order to measure the effectiveness of recycled materials in asphalt application, three various amounts of RAP replacement is considered in this research. Besides, supplementary softer binder modified with crumb-rubber and waste engine oil is added to the RAP mixtures, and the performance of green mixtures are compared with the virgin mixture based on mechanical property, environmental impact, and economic benefit criteria. 10

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4.1. Mechanical properties This section investigates the effect of a high percentage of RAP with different additives on the mechanical properties of the asphalt mixture. As stated in previous researches, the asphalt mixture fabricated with a high percentage of RAP and rejuvenator may have some deficiency including the poor rutting performance and high moisture susceptibility due to the excess amount of rejuvenator, prone to cracking through the aged binder of RAP. Therefore, Marshall Stability test, indirect tensile strength test, tensile strength ratio (TSR), semi-circular bending test at low temperature, and semi-circular bending test at intermediate temperature were conducted to assess the mechanical properties of the virgin and RAP mixtures. Moreover, to elaborate the storage stability and phase separation of CRM modified asphalt binder and the effect of WEO on these characteristics, the Storage stability test was conducted. Three replicates were tested for mixtures, and the average of experimental tests is taken into account as the result of the aforementioned tests. To analyze the impacts of recycled material on asphalt pavement more meticulously, analysis of variance (ANOVA) has been conducted in Minitab 2018 edition. By virtue of this statistical analysis, it can be scrutinized that the effects of which materials are statistically significant in the performance of asphalt pavement. In this study, stability in Marshall test, maximum force in IDT test, fracture energy in SCB test at low temperature and J-integral (Jc) in SCB test at intermediate temperature are considered as response variables in order to analyze the influences of recycled materials on the mechanical performance. The 5% of reliability is taken into account as the level of confidence. Therefore, a P-value lower than 0.05 indicates that the effect of the specific parameter is statistically significant for the confidence level of 95%. Besides, the Tukey method has been utilized to compare the means of all possible pairs and to spot the means which are significantly different from each other (Yu et al., 2017; Karimi et al., 2018). 4.1.1. Storage stability test The cigar tube test was used to assess the high-temperature storage stability of the modified asphalt binder. The samples were put vertically in the oven. The temperature was set to 160°C, and the samples remain there for 48 hours. Subsequently, the specimens were cooled to the room temperature. Then, they were taken apart into three equal part according to the previous investigations (Ghaly, 2008; Sun et al., 2006; Jahanbakhsh et al., 2017). Sample preparation, specimen fabrication, and temperature conditioning were conducted according to the instruction of ASTM D7173-05. To evaluate the storage stability, the softening point test was conducted on the prepared binders. In the case of more than 2.2°C difference in the softening point of the top and bottom samples, the binder is not stable (Sun et al., 2006; Zhang and Hu, 2013). In this part, five different types of the modified binder, including the various amounts of crumbrubber, sulfur, and waste engine oil are compared with the supplementary softer binder. The results of the storage stability test are illustrated in Fig. 5. The Neat, CRM, and CRM-x are the supplementary binder, the neat binder modified by crumb-rubber, and the neat binder with the addition of CRM and a crosslinking agent, respectively. Moreover, CRM-x-3W, CRM-x-5.7W, 11

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CRM-x-8.9W are the neat binder modified by crumb-rubber and sulfur with the addition of 3%, 5.7%, and 8.9% waste engine oil, respectively. As can be inferred from Fig. 5, Neat and CRM-x3W prevail the other binders, and they are the most stable binders since the differences of their top and their bottom softening point equal to 0. Additionally, by increasing the content of waste engine oil, the difference is increased, and the stability is deteriorated. This can be attributed to reducing the specific gravity of asphalt binder after addition of WEO resulting in the crumb-rubber to settle down due to the high specific gravity and aggregate in the bottom section. However, all the binders contained waste engine oil is stable enough, and their variances are less than 2.2°C. On the other hand, CRM is the only binder which the differences between its top softening point and the bottom softening point are more than 2.2°C, and it is 4°C. Using crumb rubber without sulfur deteriorates the results of the storage stability test. Therefore, it can be comprehended that sulfur improves the stability of crumb-rubber binder, and it has been used in all of the samples contained crumb-rubber in the following parts of this investigation. Insert Fig. 5. 4.1.2. Marshall Stability test The Marshall Stability test is often used to determine the volumetric properties of mixture and to evaluate the stability and flow of the specimens. The stability of the mixtures is gauged by measuring the maximum load endured by the test specimen at a loading rate of 2 inches/minute. Generally, the load increased until the maximum amount of load is reached, and then, the load is reduced due to the failure and softening in the specimen. After the loading process, the maximum amount of load is recorded. During the loading process, the flow of samples is gauged by a dial. The value of flow is evaluated in 0.25mm increments at the same time that the maximum load is recorded (Chen and Wang, 2018). The results of the stability and flow of various mixtures are illustrated in Fig. 6 and Fig. 7, respectively. Insert Figs. 6 and 7. As can be perceived from Fig. 3, RAP has a positive effect on stability, and by augmenting the content of RAP in specimens, stability is increased considerably. Hence, it causes to enhance loading capacity and to improve rutting resistance. The higher Marshall stability of the mixture containing different percentages of RAP can be related to the stiffening effect of reclaimed asphalt pavements. It is noticeable that the asphalt specimen will be more brittle and prone to deterioration at intermediate and low temperatures as the stiffness of mixture increases. The results of the asphalt mixture flow illustrated in Fig. 4 is in agreement with the abovementioned discussion. Based on the results depicted in Fig. 4, it can be postulated that the stiffening effect of RAP diminished the flow of asphalt mixture through the increase of the mixture brittleness. According to Fig. 4, the least flow is related to RAP specimens, which contain 100% RAP. Although adding crumb-rubber 12

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modified asphalt to the RAP mixtures decreased stability, however, the reduction of stability is not remarkable. Besides, the impact of CRM on the flow characteristics of asphalt concrete was negligible. To overcome the stiffening effect of RAP, waste engine oil might be a useful additive. Besides, the flow performance is deteriorated as the RAP is added to the mixtures. Similarly, waste engine oil remunerates this deficiency by increasing the flow. Since the waste engine oil increases the viscous phase of saturates, aromatics, and resins (maltene phase) in asphalt binder leads the ductility of prepared asphalt mixture to increase. It can be argued that by adding WEO to asphalt concrete containing RAP, the fabricated mixture acts more ductile, which results in the Marshall flow to improve (See Fig. 4). To sum up, WEO increases the ductility and compensates for the stiffness of the RAP mixtures. Therefore, drawing on the Marshall Stability test, the performance of the virgin mixture and RAP mixtures containing WEO are approximately identical. Insert Table 2. To analyze the effect of recycled materials on the performance of asphalt pavement, ANOVA analysis is conducted, and its result is shown in Table 2. As can be seen, the P-value of modified crumb-rubber (CRM-x) in Marshall Flow test is more than 0.05 (0.706). It can be deduced that the impact of modified crumb-rubber on the flow of specimens is not significant. Notwithstanding, the other P-values are lower than 0.05, and their influences on performance are statistically significant. The results of Tukey pairwise analysis is shown in Table 3. Regarding this table results, the performance of R60-CRM-x-WEO, and R30-CRM-x-WEO based on stability and flow tests are the same as that of the neat mixture because they are located in the same group. The discrepancy of R100-CRM-x-WEO and virgin mixture is not considerable. Furthermore, the stability of RAP mixtures containing WEO is by far lower than that of RAP mixtures. However, the flow characteristics of these mixtures were significantly better than that of RAP mixtures. Insert Table 3. 4.1.3. Indirect tensile strength test Fatigue cracking resistance is one of the most important criteria to assess the performance of asphalt pavements. Thus, the IDT test is usually taken into consideration to evaluate indirect tensile strength of various mixtures. IDT test provides information about the horizontal and vertical loading, and the crack initiation (Karimi et al., 2017, 2018). This test is performed based on ASTM D6931. The specimens are tested at 25°C. Under this circumstance, the sample with a height of 63.5 mm and the diameter of 101.6 mm is loaded. The loading process is fulfilled in the radial direction with the rate of 50.8 mm/min. The indirect tensile strength of asphalt specimen acquired through the IDT test is a function of peak load and geometrical characteristics of the specimen, such that: St 

2000  P   Dt

(1)

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where St denotes indirect tensile strength (kPa), D and t are the diameter and thickness of specimens (mm), respectively, and P is the peak load (N). Fig. 8 shows the indirect tensile stress acquired from IDT test. The results show that the most indirect tensile strength is relevant to R100 mixture. A more detailed look at the results reveals that increasing the content of RAP in the mixtures leads to enhancing the indirect tensile strength. This can be attributed to lower stress and strain concentration in asphalt mixture containing a high percentage of RAP due to the stiff binder of RAP and also based on the supplementary binder added to the mix. In the same way, modified crumb-rubber has an important role to play in the fatigue cracking resistance, and the addition of crumb-rubber makes the indirect tensile strength increase. On the other hand, waste engine oil may be the reason for the deterioration in indirect tensile strength because the mixtures contained waste engine oil have the least amount of indirect tensile strength. These results are quite expected since WEO meaningfully decrease the stiffness of RAP binder, causing the indirect tensile strength of mixture to decrease. Although WEO is detected as a destructive material, the RAP and crumb-rubber compensate for this deficiency and the performance of all green mixtures are roughly better than or equal to that of the virgin mixture. The results of the ANOVA analysis for the IDT test is shown in Table 4. With the assistance of this analysis, the effect of green materials on the indirect tensile strength can be analyzed meticulously, and it can be comprehended that whether the influence of each recycled material on performance is significant or not. Drawing on these results, the P-value of all refined materials are less than 0.05, and it shows that the impacts of RAP, crumb-rubber, and waste engine oil on the indirect tensile strength are statically significant for the confidence level of 95%. The Tukey pairwise comparison is conducted, and its result is implied in Table 5. The outcomes of this table indicate that the performance of R100 is by far better than that of other mixtures. Moreover, RAP and crumb-rubber play a decisive role in increasing indirect tensile strength. Even though waste engine oil reduced the indirect tensile strength, using waste engine oil, crumb-rubber, and RAP simultaneously provides appropriate mixtures which their performance are at least equal to that of the virgin mix. Insert Fig. 8 and Tables 4 and 5. 4.1.4. Semicircular bending test at intermediate temperature Fracture characteristic of asphalt mixtures is one of the pivotal criteria that should be scrutinized to design a durable asphalt mixture. There are several different test methods which analyze the cracking resistance through the fracture mechanics. Among these alternatives, the SCB test is one of the best technique which has attracted growing attention because it is a straightforward method, and its implementation cost is not considerable (Hakimelahi et al., 2013). Additionally, in SCB test method, sample preparation and making specimens is simple, its repeatability degree is high, and the impact of sample weight on the results of fracture characteristic is negligible (Monney and Khalid, 2007). Moreover, it is postulated that fatigue cracking resistance of asphalt concrete (Kim 14

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et al., 2012) and cement emulsified asphalt mixture (Jahanbakhsh et al., 2019, Moghadas Nejad et al., 2017) can be easily assessed by SCB test at intermediate temperature. IDT test at intermediate temperature is not competent to analyze crack propagation (Karimi et al., 2018). So, in this investigation, the SCB test including viscoelastic-based strain energy release rate (i.e., Jc or J-integral) has been employed. The J-integral is defined as the potential differences of energy between loaded samples possessing different notch length, and it expresses the amount of external energy in order to propagate the crack in the specimens. Therefore, the higher value of J-integral implies higher fatigue cracking resistance (Karimi et al., 2019). The diameter and thickness of specimens are considered 150 mm and 57 mm in the order given. The various specimens with different notches length (i.e., of 25.4 mm, 31.8 mm, and 28.0 mm) and with the width of 3mm were monotonically loaded by a universal testing machine at 25°C, and the loading rate is considered 0.5 mm/min. The temperature conditioning, test method, and specimen fabrication were implemented according to ASTM D8044-16. The failure strain energy (U) is the beneath area of the load-displacement curve until the fracture point (i.e., until the peak load) is then evaluated for each sample with different notch lengths. Subsequently, the J-integral was computed by Eq. (2) (Jahanbakhsh et al., 2019).

 1  U Jc      b  a

(2)

where Jc is the release rate of critical strain energy (J/m2), b is the thickness of specimen (m), a is the notch length (m), and U is the strain energy to failure (N.m). Fig. 9 indicates the outcomes of SCB test at intermediate temperature. As can be seen from the results of the figure, the addition of RAP up to a particular level improves the release rate of critical strain energy. Nevertheless, increasing the content of RAP more than this specific level makes the mixtures brittle and causing the J-integral to reduce and, consequently, to deteriorate the crack propagation resistance. This can be related to reducing tensile strain based on the stiffness of mixture fabricated with 30% of RAP and the effect of softer supplementary binder added to the asphalt mixture. Moreover, modified crumb-rubber remarkably increases the release rate of critical strain energy and enhances the crack propagation characteristic. This observation can be attributed to the substance of crumb-rubber, which reduces the brittleness of mixtures. Likewise, the addition of waste engine oil has a significant decisive role to play in increasing the J-integral. Waste engine oil raises the ductility level of asphalt samples through softening the effect of this additive on the stiffed Rap binder and increasing the release rate of critical strain energy of mixtures contained waste engine oil can be because of this increase in ductility. To sum up, the addition of RAP in low percentages, crumb-rubber, and waste engine oil reduces the rate of crack propagation and enhances the performance of asphalt pavements. Although adding high content RAP to the mixtures without any modifier deteriorates the release rate of critical strain energy due to the harder binder of RAP, however utilizing high content of RAP, waste engine oil, and crumb-rubber

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simultaneously compensates for this deficiency and under this circumstance, the J-integral reaches to climax. The ANOVA analysis results carried out based on the SCB test results at the intermediate temperature is presented in Table 6. The outcomes of analysis denote that the P-values are lower than 5%, revealing that the influences of all recycled materials (i.e., RAP, crumb-rubber, and WEO) on the crack propagation is statistically significant. Furthermore, Tukey pairwise comparison is utilized to compare the mixtures according to their performance based on J-integral. The results of the Tukey pairwise comparison is demonstrated in Table 7. Drawing on the results, the best performance is relevant to R60-CRM-x-WEO. Moreover, through the results of Table 7, the mixture containing a lower percentage of RAP which had a higher amount of supplementary binder had more fatigue cracking enhancement through the crumb-rubber modified asphalt than that of the mixtures containing WEO rejuvenator. Therefore, it can be postulated that the impact of the modified softer binder was more fruitful than that of WEO. Besides, the performance of all mixtures containing RAP, waste engine oil, and crumb-rubber simultaneously is by far better than that of the performance of the virgin mixture. The results of this analysis are in agreement with the results of the analysis of experimental results. Insert Fig. 9 and Tables 6 and 7. 4.1.5. Semicircular bending test at low temperature As mentioned previously, due to increasing the stiffness and consequently the thermally induced stress, RAP mixtures are more prone to low-temperature cracking (Riccardi et al., 2017; Majidifard et al., 2019), and low-temperature cracking is one of the most challenging concerns in the production of asphalt concrete containing RAP. Accordingly, low-temperature characteristic of modified mixtures is compared with the virgin mixture by SCB test at low temperature. Moreover, SCB test is a potentially powerful and advantageous method to address the asphalt thermal cracking (Jahanbakhsh et al., 2017; Jahanbakhsh et al., 2018). In this study, the thickness and width of specimens are considered 25 and 15 mm, respectively. Then, the notch with 2-mm width and 15-mm length was monotonically loaded by a universal testing machine under the rate of 0.6 mm/min at -20°C. According to the relevant specification (AASHTO TP 105-13), the fracture energy (Gf) has been considered as the main criterion to compare the low-temperature performance of various mixtures because it is a primary feature of mixtures and is less dependent on the homogeneity of materials and LEFM than that of fracture toughness. The fracture energy is the implication of energy needed for crack propagation, and the impacts of modifiers can be easily characterized in this method (Jahanbakhsh et al., 2019). In this research, Gf is obtained according to RILEM TC50-FMC specifications, as indicated in Eq. (3).

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Gf 

w0 Alig

(3)

D  Alig    a   t 2 

where Gf is the fracture energy, w0 is the fracture work (N.m), Alig is the ligament area (m2), D is the diameter of the specimen (m), a is the length of the notch (m), and t is the thickness of specimen (m). The result of the SCB test at low temperature based on Gf is illustrated in Fig. 10. As can be perceived, due to the high stiffness of existing asphalt binder in RAP and brittleness of asphalt concrete, the fracture energy seamlessly decreases as the content of RAP in asphalt concrete increases. As a matter of fact, RAP mixtures are fragile, and it may be the reason for fracture energy reduction. On the flip side, crumb-rubber and waste engine oil make the mixtures more ductile and flexible. Hence, the ductility created by waste engine oil and crumb-rubber can compensate for the stiffness caused by RAP. Additionally, the performance of mixtures, including RAP, waste engine oil, and crumb-rubber concurrently, is approximately the same as the virgin mixture. Therefore, it can be a fruitful technique to add waste engine oil and crumb-rubber modified softer binder to RAP mixtures in order to enhance low-temperature resistance. Based on the results shown in Fig. 10, the asphalt mixture containing the lower amount of RAP (i.e., 30%) had more improvement in low temperature cracking resistance when the crumb-rubber modified softer binder was added to the mixture than that of WEO rejuvenator. This finding accords with the results of the asphalt mixture with a high percentage of RAP. As can be seen from the consequences, the R 100 specimen after addition of WEO and a small amount of soft binder had lower enhancement than that of RAP 60 and RAP30. This finding is in accordance with the finding of Zaumanis et al. (2014b) which argued that WEO rejuvenator could not fully recover the cracking resistance of asphalt mixtures containing a high percentage of RAP at low temperatures. The results of the ANOVA analysis of fracture energy is presented in Table 8. Referring to the results of Table 8, the P-values of all refined materials are lower than 0.05. Ergo, it can be realized that the impacts of these recycled materials on the fracture energy of asphalt mixture are significant with the confidence level of 95%. The results of the Tukey pairwise comparison of different mixtures are shown in Table 9. The outcomes of this table indicate that the most amount of fracture energy is related to the specimens containing WEO, crumb-rubber, and the least content of RAP (30%). Furthermore, R30-CRM-x, R60-CRM-x-WEO, R100-CRM-x-WEO, and the virgin mix placed in the same group, and it can be postulated that their performance is virtually identical. Accordingly, the low-temperature performance of samples made by RAP, waste engine oil, and crumb-rubber is approximately equal to that of the virgin mixture, and in the circumstances that the amount of RAP is not high in the mixes, they outperform the virgin mix. The results of ANOVA analysis and the Tukey pairwise comparison are consistent with other parts of the investigation, and they validate the findings of fracture energy resulted from analysis of experimental tests. 17

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Insert Fig. 10 and Tables 8 and 9. 4.1.6. Tensile strength ratio One of the most critical characteristics of asphalt pavement is their durability through the moisture susceptibility. Indirect tensile strength ratio is a commonly used test method ensuring the mixture resistance against long-term stripping. To evaluate the moisture susceptibility of various mixtures, tensile strength ratio was carried out in this study. Therefore, for each mixture design, six specimens with the size mentioned in section 3.1.3 were made. Similar to the conditioning of the IDT test, half of the samples (i.e., three specimens) are kept dry, and the other three samples undergo the wet conditioning according to AASHTO T283-03. Afterward, the three replicates were tested for wet and dry conditioning samples. Subsequently, the average value of indirect tensile strength of wet and dry specimens was compared (Moghadas Nejad et al., 2017). Tensile strength ratio defines as the ratio of the average value of IDT of wet samples to that of dry samples. The results of the IDT test for wet and dry mixtures are shown in Fig. 11. According to results, the most amount of TSR is relevant to R60-CRM-x followed by R100, R30-CRM-x, R60, R30, R30CRM-x-WEO, R100-CRM-x-WEO, virgin, and R60-CRM-x-WEO with the TSR value of 90.8, 88.6, 88.4, 87.3,85.9, 83.7, 80.3, 80.3, and 80, respectively. Thus, it can be postulated that the addition of RAP to the mixtures increase the TSR value, and moisture susceptibility improves as the content of RAP increases. This trend can be attributed to the coated aggregates of RAP with hard binder leading to the lower capability of water to penetrate into aggregate-binder bonding interface and therefore, resulted in a less destructive effect on the mechanical properties. Furthermore, it should be worth mentioning that the impact of supplementary binder could not be ignored. Similarly, crumb-rubber has a positive effect on moisture behavior, and these recycled materials enhance the performance of asphalt pavement. On the other hand, waste engine oil is the destructive parameter of TSR, and moisture susceptibility increases as waste engine oil is added to the samples. Waste engine oil increases the molten phase of asphalt, and it makes the asphalt reactive with moisture and oxidation, and this phenomenon may be the reason for the reduction in TSR. According to AASHTO T283-03, in the case of less than 80% for the ratio of wet samples IDT average value to dry samples IDT average value, the mixture is susceptible to moisture. The TSR value of different mixtures is demonstrated in Fig. 12. A more detailed look at Fig. 12 indicates that the indirect tensile strength ratio of mixtures is higher than 80%, revealing the desirable moisture susceptibility of proposed mixtures. That is to say, all mixtures designed in this investigation suitably passes the requirement of the standard, and their TSR value is higher than the limitation set in AASHTO T283-03. Insert Figs. 11 and 12.

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This paper aims to compare the performance of green mixtures with a virgin mixture. The rutting, fatigue cracking, low-temperature cracking, and moisture susceptibility are the most important criteria to assess the performance of RAP mixtures. Thus, these factors have been evaluated by various experimental tests and statistical analyses. Concerning previous parts of this study, the mechanical performance of mixtures containing RAP, crumb-rubber, and waste engine oil concurrently are equal to or better than that of the virgin mixture. In other words, by considering mechanical characteristics and environmental effects, the conventional asphalt mixtures can be economically replaced with the green mixtures introduced in this study. 4.2. Environmental impacts Transport infrastructure plays a critical role in the universe, and there are extensive road networks around the world paved by asphalt concrete. There are more than 4.68, 3.68, 0.41, 0.17, and 3.8 million km of roads in Europe, the United States, Canada, Mexico, and Asia, respectively, which paved with asphalt concrete surface (NAPA, 2011). Developing countries, increasing the traffic, the growth of business activities, exports and value creation, and the focus for infrastructure investment lead these paved roads to expand, and new roads are added to the networks instantly. Construction of new roads, maintenance, rehabilitation, reconstruction, and preservation of aged pavements need a massive volume of materials and consume unreproducible energy. Besides, during these processes, dangerous gasses are emitted, and landfills are generated, which are the perilous and threatening factor for the Environment. Conclusively, the negative influences of the pavement industry have been a significant concern. According to the results provided by EAPA (EAPA, 2015), the total production of asphalt in 30 European countries, the United States, and Japan from 2008 to 2015 is presented in Table 10. Referring to this table results, 5485.3 million tons of asphalt were produced in 32 countries for 8 years. The amount of worldwide asphalt production is much more than this amount. This information proves that the amount of asphalt production is extremely high, and analyzing the environmental effects of asphalt manufacturing is vital to preserving the environment. As mentioned in the introduction, using refined materials such as RAP, waste engine oil, and crumb-rubber in the pavement industry has considerable positive effects on the environment. Embedding waste materials, industrial by-products, and landfills is a great enterprise, let alone the reduction of energy consumption and greenhouse emissions are added to those pros. In this study, embedding volume of waste landfills, the amount of greenhouse gas emission, and energy consumption are considered as the criteria which considerably affect the environment. Thus, all the examined mixtures are compared based on these parameters selecting eco-friendly green asphalt concrete. Additionally, the impacts of all mixtures on the environment are analyzed. In order to compare the environmental value of studied mixtures, the energy consumption and the carbon dioxide (CO2) emission of material used in this study have been extracted from international articles (Zaumanis et al., 2014a; Chen and Wang, 2018; Xiao et al., 2019, Ughwumiakpor et al., 2017, IERE, 2009) which are given in Table 11. Insert Tables 10 and 11. 19

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According to Table 12, the energy consumption and CO2 emission of waste engine oil production is equal to 0 because this material is directly added to the mixtures and there is not any preprocess for preparing waste engine oil. Furthermore, a range is considered for some parts of the table, and in this investigation, the average of the lower and upper bound of these ranges is taken into account for the amount of energy consumption and CO2 emission. The energy consumption and CO2 emission of examined asphalt mixtures are calculated based on the weight of materials used in mixture proportion and the operations to produce the specimens. The outcomes of energy consumption and also CO2 emission analysis are demonstrated in Figs. 13 and 14, respectively. Insert Figs. 13 and 14. Regarding the results of Fig. 13, it can be inferred that reclaimed asphalt pavements significantly reduce the energy consumption of asphalt concrete. By increasing the content of RAP in the specimens, the needed energy to cast the samples reduces considerably, and the unit energy reaches its lowest level when the replacement of RAP is 100%. Moreover, the addition of crumb-rubber and waste engine oil lead to decrease the unit energy consumption, but this saving energy is not remarkable. Referring to Fig. 14, the trend of CO2 emission is approximately the same as the energy consumption trend. In the same way, by the addition of RAP to the asphalt concrete, the amount of CO2 emitted by the production process is reduced remarkably. In addition, the CO2 emission of specimens, including 100% RAP is the lowest, and this amount of emission is by far lower than that of the virgin mixture. Although waste engine oil and crumb-rubber have a decisive role to play in the reduction of CO2 emission, the amount of CO2 reduction by the addition of these refined materials is not substantial. The environmental performance of the mixture containing 100% RAP, crumb-rubber, and waste engine oil concurrently is marvelous, and it can opt for the greenest mixture proportion. Comparing the environmental impacts of R100-CRM-x-WEO with the virgin mixture shows that R100-CRM-x-WEO is competent to reduce the needed energy for manufacturing and the emission of CO2, 52% and 49%, respectively. Roughly, 25% of fossil fuel consumption and 30% of global air pollution is relevant to transportation sector (Mallick and Veeraragavan, 2010), and more than 7% of these contents is the contribution of pavement industry ( Piantanakulchai et al., 1999). Ergo, vast amounts of unreproducible fossil fuel can be saved, and worldwide air pollution can be decreased in case of replacing the conventional asphalt pavement with the R100-CRM-x-WEO designed in this study. Regarding the information of Table 10, 1757.6 billion MJ energy could be saved in only 32 countries in an 8-year-period. Furthermore, generation of 126.5 billion Kg CO2 will be prevented in those countries. By considering the production of asphalt in the world, these amounts of saving would be increased dramatically. The primary purpose of this paper is to investigate the mixture design of asphalt pavement containing a high content of RAP to introduce an eco-friendly mixture which reduces the negative influences of pavement application on the environment. Thus, the primary concentration of this study is to scrutinize the effects of materials applied to manufacture asphalt pavement, and the process of HMA operation is not taken into consideration which is similar in all examined mixtures. The energy consumption (Figs. 15) and CO2 emission (Figs. 16) caused by asphalt materials are analyzed. Fig. 15 provides details about the needed energy to produce the materials of a ton asphalt for various mixtures. A more detailed look at the results of this figure reveals that 20

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refined materials need a lower level of energy to be prepared rather than virgin materials. Besides, the consumption energy of RAP is by far lower than the binder and virgin aggregates, and by the addition of the amount of RAP in the asphalt concrete, the energy consumption of materials preparation drops remarkably. The materials-based energy consumption of the virgin mixture and R100-CRM-x-WEO are 344.7 MJ, and 24.3 MJ, respectively. In other words, the needed energy to produce the materials of the mixture containing 100% RAP, crumb-rubber, and waste engine oil is nearly 93% less than that of the conventional mixture. Insert Figs. 15 and 16. On the other side of the flip, some other emissions are deteriorating the environment, and they should be considered to analyze the quality of the environment. In this investigation, CH4, the volatile organic compound (VOC), nitrogen oxides (NOx), carbon monoxide, sulfur dioxide (SO2), particulate matter 10 micrometers or less in diameter (PM10) are considered as the pollution which hurt the environment. The amounts of this emission generated by materials and HMA process is shown in Table 12 (Yu et al., 2014). The pollution related to waste engine oil and RAP is equal to 0 because these landfill materials are directly added to the mixture, and they do not need any special preprocessing. Insert Table 12. Drawing the consequences of Table 12, the amounts of pollutions emitted by surveyed mixtures are assessed, and the outcomes are demonstrated in Table 13. According to the pollution analysis, using refined and waste materials in the asphalt mixtures reduces the amounts of pollutant emissions because the production of virgin materials and binder need operation and process which cause to emit pollution and deteriorate the environment. Nonetheless, the RAP and waste engine oil can be used in asphalt without any process, and the emission of granulating crumb-rubber is much fewer than producing binder. Hence, the results of this section are in line with the results previous parts of this study and utilizing refined materials can reduce the pollution caused by pavement application and protects the environment. Additionally, R100-CRM-x-WEO is the greenest mix which can reduce the emission of CH4, VOC, NOx, CO, SO2, and PM10 97%, 97%, 22%, 39%, 5%, 19% respectively. Accordingly, the pollution generated by the pavement industry can be decreased considerably, and it helps the agencies to promote the sustainability of the environment. According to Table 10, by virtue of R100-CRM-x-WEO, the amounts of CH4, VOC, NOx, CO, SO2, and PM10 generated by only 32 countries could be reduced 6.2, 3.6, 69, 13.7, 11.7, and 3.8 million Kg in the environment in an 8-year-period. Insert Table 13. Fig. 17 provides information about the pollution generated by the production and preparation of materials to manufacture different mixtures. A comprehensive look at this figure indicates that the materials-based pollutions created by mixtures included waste materials is considerably lower than that of the virgin mixture. Moreover, it can be postulated that by increasing the content of refined materials to the mixture, the emission of various pollutant is reduced dramatically. The lowest 21

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value of emissions is related to the R100-CRM-x-WEO mixture. If the conventional mixture is replaced with the R100-CRM-x-WEO, the generation of CH4, VOC, NOx, CO, SO2, and PM10 in materials production and preparation phase is dropped 97%, 98%, 99%, 99%, 98%, and 99%, respectively. Hence, by utilizing R100-CRM-x-WEO in pavement application, the amount of mentioned harmful emissions can be prevented. Insert Fig. 17. One of the essential criteria to protect the environment is the volume of waste materials embedded in the asphalt concrete samples. Hence, all of the introduced mixtures are compared based on this parameter, and their percentage of landfill reduction is indicated in Fig. 18. That is to say, the amounts of landfill percentage are defined as the unit volume of waste materials in the mixtures. As can be perceived from the results of Fig. 18, the most amount of landfill percentage is relevant to 100% RAP mixtures. In these asphalt concretes, the unit volume of recycled material is nearly 99%, and this can lead to preserving the environment. The landfill percentage is raised while higher content of RAP is utilized in the specimens. If the R100-CRM-x-WEO had used to produce asphalt between 2008 and 2015, 5422.5 million tons of unreproducible materials would have been saved, and 5422.5 million tones would have embedded in the pavements in Europe, Japan, and the USA. Insert Fig. 18. 4.3. Economic analysis The economic benefit is one of the most important criteria to choose an option among several alternatives. Considering the gap between limited road construction and maintenance funds and costly new projects, agencies have been investigated the novel methods to reduce the expenditures of pavement expansion. Ergo, economic analysis and life-cycle cost have been attracted attention in recent years (Wu et al., 2017). Cost analysis is usually classified into two approaches as (1) decreasing the price of asphalt pavements, and (2) reducing the materials related cost. In this study, various mixture proportions are designed, and HMA operation is not taken into consideration due to the feasibility of making these mixtures by conventional equipment. Therefore, the primary aim of this study is to scrutinize the second approach, which is materials related-cost analysis while the other approach is either investigated. To compare the manufacturing cost of different asphalt mixtures, the authentic unit price of materials and HMA operation are extracted from the international articles, and it is presented in Table 14. Regarding the values of Table 14, the manufacturing price of the designed mixtures is demonstrated in Fig. 19. Concerning the results of the analysis, the manufacturing price of green asphalt pavements is by far lower than that of the conventional mixture. All the specimens included refined materials are more economical than the virgin mix. The cheapest cost is relevant to the mixture containing 100% RAP, waste engine oil, and crumb-rubber simultaneously, and this mixture reduces the unit price of asphalt from 66.4$ to 17$. Accordingly, the R100-CRM-x-WEO approximately has a 74% reduction in the cost of asphalt mixture.

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As mentioned in the previous section, 5485.3 million tons of asphalt were made in 32 countries from 2008 to 2015. Hence, if the conventional asphalt had replaced with R100-CRM-x-WEO, the expenditure of asphalt production would have reduced 270.5 billion dollars. Besides, this reduction is related to 32 countries, and if the worldwide asphalt production is taken into account, the amount of financial saving would be augmented. Hence, it can be postulated that using waste materials in pavement applications not only preserves the environment but also reduces the manufacturing cost considerably. The cost of materials used in studied mixtures are also calculated, and it is indicated in Fig. 19. As can be seen from this figure, by increasing the content of RAP in asphalt concrete specimens, the unit price of materials is reduced considerably. In the same way, the materials based unit price reaches its lowest level when crumb-rubber and waste engine oil are added to the samples, and the content of RAP is considered 100%. Furthermore, it can be realized that the R100-CRM-x-WEO mixture roughly reduces 91% of the materials price rather than the virgin mixture. Insert Fig. 19 and Table 14. 5. Conclusion In this study, the aim is to scrutinize the feasibility of manufacturing sustainable asphalt mixtures. In order to achieve the mentioned purpose, mechanical performance, environmental impacts, and financial benefit are taken into consideration. The results of the Marshall Stability test, indirect tensile strength test, tensile strength ratio, semi-circular bending test at low temperature, and semicircular bending test at intermediate temperature are considered as mechanical performance indicators. Moreover, saving in energy consumption, and the percentage of embedded landfill and the amounts of harmful emissions including carbon dioxide, methane, the volatile organic compound, nitrogen oxides, carbon monoxide, sulfur dioxide, and particulate matter 10 micrometers or less in diameter are analyzed to evaluate detrimental influences of various mixtures on the environment. These criteria are analyzed in two approaches: material based analysis, and asphalt mixtures analysis. The following conclusions can be drawn from the results of this study: 



Addition of RAP to the mixtures deteriorates the fatigue cracking performance, lowtemperature cracking, and moisture susceptibility. Furthermore, rejuvenators are the destructive parameter in rutting resistance. However, these deficiencies are not that much in the low content of RAP (R30-CRM-x-WEO), but by utilizing high RAP, the high stiffness of RAP binder makes the mechanical performance of mixture to degrade. To compensate for these deficiencies, employing rejuvenator, and CRM modified softer binder, three mixtures are designed (R30-CRM-x-WEO, R60-CRM-x-WEO, and R100CRM-x-WEO) which their mechanical performance are equal to or better than that of the virgin mixture. Approximately, a fourth of fossil fuel consumption and a third of global air pollution is related to pavement application. Hence, the quality of the environment can be enhanced considerably by introducing sustainable asphalt mixtures. The R100-CRM-x-WEO is known as the greenest asphalt followed by R60-CRM-x-WEO, and R30-CRM-x-WEO. Comparing with conventional asphalt mixture, R100-CRM-x-WEO approximately reduces 23

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

the emission of CO2, CH4, VOC, NOx, CO, SO2, and PM10 49%, 97%, 97%, 22%, 39%, 5%, and 19%, respectively. The energy consumption in producing R100-CRM-x-WEO is 52% lower than that of the virgin mix. Besides, the percentage of landfill embedded by R100-CRM-x-WEO is 99%, which is remarkable. Additionally, CO2, CH4, VOC, NOx, CO, SO2, and PM10 emitted by manufacturing R60-CRM-x-WEO roughly can be decreased 29%, 60%, 60%, 13%, 24%, 3%, and 11% in the order mentioned. Furthermore, R30CRM-x-WEO can diminish the emission of CO2, CH4, VOC, NOx, CO, SO2, and PM10 nearly 16%, 33%, 34%, 7%, 13%, 2%, and 6%, respectively. The energy consumed to manufacture R60-CRM-x-WEO, and R30-CRM-x-WEO is 70%, and 84% of that of the conventional mixture. The landfill reduction of R60-CRM-x-WEO and R30-CRM-x-WEO are 57%, and 27% in the order named. According to the limited fund of agencies and the need to expand new roads and the high costly maintenance activities, economics is one of the most important criteria which has to be optimized in pavement applications. All the sustainable mixtures introduced in this investigation are cost-beneficial because the low priced refined materials are replaced with expensive virgin materials. R100-CRM-x-WEO can reduce the manufacturing and materials cost 74%, and 91% respectively, and it is the most economical mixture followed by R60-CRM-x-WEO, and R30-CRM-x-WEO. The unit price of producing mixture and materials preparation can be decreased by 45%, and 54% in case of replacing virgin mixture with R60-CRM-x-WEO. Furthermore, utilizing R30-CRM-x-WEO rather than virgin mixture leads to saving 23%, and 28% of the budget in manufacturing approach and materials-based approach.

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Figures Captions Fig. 1. Gradation curve of aggregate (NMAS 12.5 mm). Fig. 2. (a) Penetration; (b) Softening Point; (c) Ductility of RAP binder with different percentage of WEO. Fig. 3. The viscosity of RAP binder with different WEO percentage. Fig. 4. The PVN number of RAP binder with different percentage of WEO. Fig. 5. Top and bottom softening point of various binders. Fig. 6. Stability of examined mixtures in Marshall Stability test. Fig. 7. The flow of examined mixtures in Marshall Stability test. Fig. 8. The indirect tensile strength of different mixtures. Fig. 9. The critical strain energy release rate of examined mixtures. Fig. 10. The fracture energy of various mixtures based on the results of the SCB test at -20 ºC. Fig. 11. Indirect tensile strength of dry and wet conditioned of various fabricated mixtures. Fig. 12. Tensile strength ratio of studied mixtures. Fig. 13. The energy consumption of various asphalt mixtures. Fig. 14. The CO2 emission of various asphalt mixtures. Fig. 15. The energy consumption to prepare the materials of examined mixtures. Fig. 16. The materials-based CO2 emission of studied mixtures. Fig. 17. The pollution generated by the studied asphalt concrete materials. Fig. 18. The percentage of landfills embedded in studied asphalt mixtures. Fig. 19. The production cost of examined asphalt mixtures.

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Fig. 1.

Percent Passing (%)

120 100 80 Aggregate

60

lower Limite

40

upper Limite

20 0 0

1

2

3

4

Sieve Size Raised to 0.45 Power

2

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Fig. 2a. Penetration Test Temperature 25 ºC

Penetration (0.1 mm)

80 70 60

Penetration of Virgin Binder = 66

50 40 30 20 10 0 RAP

RAP+2WEO RAP+4WEO RAP+6WEO RAP+8WEORAP+10WEORAP+12WEO

Binder Type Fig.2b. Softening Point Test 80

Softening Point (ºC)

70 60

Softening Point of Virgin Binder = 51 ºC

50 40 30 20 10 0 RAP

RAP+2WEO RAP+4WEO RAP+6WEO RAP+8WEO RAP+10WEORAP+12WEO

Binder Type 3

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Fig. 2c. Ductility Test Temperature 25 ºC 120

Ductility (cm)

100

Ductility of Virgin Binder = 105 cm

80 60 40 20 0 RAP

RAP+2WEO RAP+4WEO RAP+6WEO RAP+8WEORAP+10WEORAP+12WEO

Binder Type

4

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Fig. 3.

4000

Test Speed = 20 RPM

Rotational Viscosity (mPa.s)

3500 3000 2500

Neat RAP RAP+2WEO RAP+4WEO RAP+6WEO RAP+8WEO RAP+10WEO RAP+12WEO

2000 1500 1000 500 0 95

105

115

125 135 Temperature (ºC)

5

145

155

165

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Fig. 4.

PVN Number of Virgin Binder = -1.24

-2

10

WEO Content (%)

12

8 6 4 2 -1

0 PVN Number

1

6

2

3

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Fig. 5. Top_Softening Point

70

60.0 56.0

Softenning Point (ºC)

60 50

Bottom_Softening Point

58.0 57.0 49.0 49.0

48.0 48.0

40

44.0 45.0

40.0 42.0

30 20 10 0 Neat

CRM

CRM-x

CRM-x-3W

Binder Type

7

CRM-x-5.7W CRM-x-8.9W

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Fig. 6. 16

Marshall Test Temperature 60 ºC

14

2 in/min

10 2.5 in

8 6

0.37 in

4 Marshall Specimen

2 EO -W

0 00

-C

-C

RM

-x

RM -x

R1 0

EO -W

RM

-x

0 -C

R1

EO

R6

R6 0

R6 0

R3 0

-C

RM

-x

-W

RM

-x

0 -C

R3

R3 0

irg

in

0 V

Stability (kN)

12

Mixture Type

8

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Fig. 7. 3

Marshall Test Temperature 60 ºC

2 in/min

2 2.5 in

1.5

0.37 in

1 Marshall Specimen

0.5

-W -x

CR M 0R1 0

Mixture Type

9

EO

0 R1 0

EO

-x

-W

RM -x CR M 0-

R6 0

-C

R6 0

EO

R6

R3

0-

CR M

-x

-W

RM -x

-C

R3 0

R3 0

irg

in

0 V

Flow (mm)

2.5

Mixture Type

10 R1

-x

EO

00

EO

R1

-W

-W

-x

RM

-C

-x

M

0

EO

-x

0

R6

-W

CR

0-

M

0CR

R6

-x

M

CR

0-

M

0CR

00

R6

R3

0.8

R3

0.9

R3

in

irg

V

Indirect Tensile Strength (MPa)

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Fig. 8.

IDT Test Temperature 25 ºC

0.7

0.6 2 in/min

0.5

0.4

0.3

0.2

0.1

0

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Fig. 9. 0.5 mm/min 75 mm

Thickness = 57 mm Notch Lengths = 25.4, 31.8, 38 mm

300

3 mm 150 mm

SCB Test Temperature 25 ºC

200 150 100 50

-W -x

-C RM 00 R1

M CR 0-

R6

EO

00

-x

R1

-W

M 0R6

M CR 0-

R3

Mixture Type

11

EO

-x

0

-x

CR

-W

M CR 0R3

R6

EO

-x

0 R3

irg

in

0 V

Jc (J/m2)

250

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Fig. 10. 0.6 mm/min 75 mm

2.5

SCB Test Temperature -20 ºC

150 mm

2

1.5

1

0.5

EO

00

-W -x M

-C R

RM -C

R1 00 R1

-x -W

M CR

Mixture Type

12

EO

-x

0

R6 0

R3 0

-C

R6

RM

0-

-x -W

M CR 0R3

R6

EO

-x

0 R3

irg

in

0 V

Fracture Energy (kJ/m2)

Thickness = 25 mm

2 mm

Mixture Type

13 RM

-C

00

W

-x -

-x

EO

00

EO R1

-W

-x

M

M

CR

0

Dry

R1

0CR

R6

0-

R6

EO

-x

M

-W

-x

M

CR

0

1.00

R6

0CR

R3

0-

R3

in

irg

0.80

R3

V

Indirect Tensile Strength (MPa)

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Fig. 11.

Wet

IDT Test Temperature 25 ºC

0.60

0.40

0.20

0.00

R3

Mixture Type

14 R1

RM

-C

W

-x -

-x

0

EO

00

EO R1

-W

-x

M

CR

0-

M

0CR

00

R6

R6

EO

-x

0

R6

-W

-x

M

CR

0-

M

0CR

R3

in

100

R3

irg

V

Tensile Strength Ratio (%)

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Fig. 12.

IDT Test Temperature 25 ºC

80

60

40

20

0

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Fig. 13. The asphalt concrete containing high RAP required significantly lower energy to produce

600 500 400 300 200 100

R1

00

-C R

M

-x -W

EO

00 R1

M

-x

-W

M CR

0CR

Mixture Type

15

EO

-x

0

R6

R3

0CR

R6

M

0-

-x

-W

M CR 0-

R6

EO

-x

0 R3 R3

irg

in

0 V

Energy Consumption (MJ/Ton)

700

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Fig. 14. By the addition of RAP to the asphalt concrete, the amount of CO2 emitted is reduced remarkably  

40 30 20 10

-W -x

R1

00

-C

RM

M 0CR

R6

EO

00 R1

-x

-W

M CR 0-

R6

M 0CR

Mixture Type

16

EO

-x

0

-x

-W

M CR 0R3

R3

R6

EO

-x

0 R3

irg

in

0 V

CO2 Emission (kg/Ton)

50

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Fig. 15. The effects of using RAP as the material for asphalt concrete on the energy consumption  

350 300 250 200 150 100 50

17

EO

00

-W -x

EO

R1 RM -C 00

Mixture Type

R1

R6

0-

CR

R6

M

0-

-x

CR

-W

M

-x

R6 0

EO M

CR 0R3

R3

0-

-x

CR

-W

M

-x

R3 0

irg

in

0 V

Energy Consumption (MJ/Ton)

400

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Fig. 16. The impacts of using RAP as the material for asphalt concrete on the CO2 emission  

20

10

-W -x

-x

R1

00

-C

RM

M CR 0-

EO

00 R1

-W

M CR 0R6

18

EO

-x

0

-x M CR 0-

R3

Mixture Type

R6

-W

M CR 0R3

R6

EO

-x

0 R3

irg

in

0 V

CO2 Emission (Kg/Ton)

30

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Fig. 17. Amounts of pollutions (gr/Ton)

O M-x-WE R100-CR R100

Mixture Type

-x-WEO R60-CRM -x

R60-CRM

R60 -x-WEO R30-CRM -x

R30-CRM

R30 Virgin R30-CRM-

R60 1

0.44 0.48 0.77 1.46 1.73 8.87

0.33 0.31 0.58 1.02 1.14 5.31

0.Virgin 2.0 R30 4.R30-CRM-x 6.0 x-WEO 8.0 00 00 0 0 0 VOC PM10 CH4 SO2 CO Nox

0.67 0.69 1.16 2.18 2.52 12.62

0.45 0.48 0.79 1.50 1.75 8.93

0.41 0.47 0.73 1.41 1.69 8.85

19

R60-CRM-

12. 14. 0.0 R60-CRM-x 00 x-WEO 00 0 0.30 0.30 0.54 0.96 1.09 5.25

0.26 0.28 0.46 0.87 1.02 5.16

R100-

CRM-x- 2 16R100 0.0 .00 18.WEO 00 0 0.09 0.04 0.16 0.21 0.17 0.21

0.02 0.01 0.03 0.04 0.03 0.04

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Fig. 18.

Landfill reduction through the addition of RAP to the asphalt concrete

80 60 40 20

-W -x RM

-x

R1

00

-C

M CR 0R6

EO

00 R1

-W

M 0R6

M CR 0R3

Mixture Type

20

EO

-x

0

-x

CR

-W

M CR 0R3

R6

EO

-x

0 R3

irg

in

0 V

Landfill Reduction (%)

100

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Fig. 19. 70

manufacturing price of the examined mixtures material price of the examined mixtures

60

40 30 20 10

21

EO

00 RM

-x

-W

R1

EO -x -W

-C 00 R1

0CR R6

R6

Mixture Type

M

0-

CR

M

-x

R6 0

EO -x -W M

0CR R3

R3

0-

CR

M

-x

R3 0

irg

in

0 V

Cost (USD/Ton)

50

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Highlights  In this study, sustainable asphalt concrete containing high reclaimed asphalt pavements was developed.  WEO, and CRM modified softer binder, compensate the deficiencies of using high RAP.

 The proposed asphalt mixtures significantly reduced the energy consumption.  Increasing the content of refined materials to the asphalt mixture, decreased the emission of various pollutant dramatically.

 The introduced asphalt concrete roughly reduces 91% of the materials price rather than the virgin mixture.

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List of Tables Table 1. Specification of utilized asphalt binders. Table 2. ANOVA analysis of the Marshall based performance of recycled materials. Table 3. Tukey pairwise comparisons of various mixtures based on Marshall Test results. Table 4. The ANOVA analysis for recycled materials based on IDT test results. Table 5. Tukey pairwise comparisons of different mixtures based on IDT test results. Table 6. The ANOVA analysis of refined materials according to J-integral. Table 7. Tukey pairwise comparison based on J-integral. Table 8. The influences of recycled materials on fracture energy introduced by ANOVA analysis Table 9. Tukey pairwise comparison of different mixtures through the SCB test at -20 º C. Table 10. Total production of asphalt in 32 countries from 2008 to 2015 (in a million tons). Table 11. The energy consumption and greenhouse emission of materials used in asphalt concrete. Table 12. The amounts of emissions produced by asphalt concrete materials and operations. Table 13. The amounts of pollutions emitted by examined asphalt mixtures. Table 14. The unit price of materials and operations for producing asphalt concrete.

1

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Table 1. Specification of utilized asphalt binders. Properties

ASTM

Density in 125°C (gr/cm3) Penetration at 25 °C Softening Point (°C) Ductility (cm) Fire Point (°C) Loss on Heating (%) Solubility in Trichloroethylene (%)

ASTM D70-76 ASTM D5-73 ASTM D36-76 ASTM D113-79 ASTM D92-78 ASTM D1754-78 ASTM D2042-76

Pen 85/100 Pen 60/70 Value 1.03 1.02 91 66 48 51 112 105 248 262 0.75 0.75 99.5 99.5

Table 2. ANOVA analysis of the Marshall based performance of recycled materials. Performance test Stability of Marshal test

Flow of Marshal test

ANOVA test results Factor RAP CRM-x Waste engine oil RAP CRM-x Waste engine oil

2

Adj. MS 10.4283 1.4911 12.1275 1.1439 0.0010 0.8429

F-value 45.76 6.54 53.22 55.80 0.15 123.36

P-value 0.000 0.018 0.000 0.000 0.706 0.000

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Table 3. Tukey pairwise comparisons of various mixtures based on Marshall Test results. Marshal stability

Marshal Flow

Factor R100

Grouping A

R60

B

R60-CRM-x

B

R30

Factor

C

R60-CRM-x-WEO

A

R30-CRM-x-WEO

A

Neat

A

D

R100-CRM-x-WEO

B

R100-CRM-x-WEO

D

R30

B

R30-CRM-x

D

R30-CRM-x

B

F

R60-CRM-x

B

R30-CRM-x-WEO

F

R60

B

R60-CRM-x-WEO

F

R100

virgin

C

Grouping

E E

C

Table 4. The ANOVA analysis for recycled materials based on IDT test results. Performance test IDT test

ANOVA test results Factor Adj. MS F-value RAP 0.0196 16.64 CRM-x 0.0051 4.36 Waste engine oil 0.0536 45.54

3

P-value 0.000 0.049 0.000

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Table 5. Tukey pairwise comparisons of different mixtures based on IDT test results. IDT test Factor R100 R60-CRM-x R60 R30-CRM-x R100-CRM-x-WEO R30 R30-CRM-x-WEO virgin R60-CRM-x-WEO

Grouping A A B B B

C C C C

D D D D D

E E E E E

Table 6. The ANOVA analysis of refined materials according to J-integral. Performance test SCB test at 25 ºC

Factor RAP CRM-x Waste engine oil

4

ANOVA test results Adj. MS F-value 2969.2 8.46 1544.6 4.40 4479.2 12.76

P-value 0.001 0.048 0.002

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Table 7. Tukey pairwise comparison based on J-integral. SCB test at intermediate temperature Factor Grouping R60-CRM-x-WEO A R30-CRM-x-WEO A B R30-CRM-x B C R60-CRM-x B C R100-CRM-x-WEO B C R30 B C virgin C R60 C R100

D D D

Table 8. The influences of recycled materials on fracture energy introduced by ANOVA analysis Performance test SCB test at low temperature

Factor RAP CRM-x Waste engine oil

ANOVA test results Adj. MS F-value 0.2132 14.40 0.2265 15.30 0.1451 9.80

5

P-value 0.000 0.001 0.005

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Table 9. Tukey pairwise comparison of different mixtures through the SCB test at -20 º C. SCB test at low temperature Factor Grouping R30-CRM-x-WEO A R60-CRM-x-WEO A B R30-CRM-x A B virgin A B R100-CRM-x-WEO A B R60-CRM-x B C R30 B C R60 C R100 C

Table 10. Total production of asphalt in 32 countries from 2008 to 2015 (in a million tons). Region

2008

2009

2010

2011

2012

2013

2014

2015

Total

Europe

338

326.9

309.3

324.3

276.4

277.3

263.7

278.8

2394.7

USA

440

324

326

332

326.9

318.1

319

331

2717

Japan

49.6

49.6

44.7

45.6

47.3

49.9

45

41.9

373.6

Total

827.6

700.5

680

701.9

650.6

645.3

627.7

651.7

5485.3

6

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Table 11. The energy consumption and greenhouse emission of materials used in asphalt concrete. Process Aggregate production RAP production Binder production Crumb-rubber production Waste engine oil production HMA operation

Energy consumption (MJ/Ton) 54 16.5 5810

(Zaumanis et al., 2014a) (Zaumanis et al., 2014a) (Chen and Wang, 2018)

CO2 emission (Kg/Ton) 10 1.3 ~ 2.3 294 ~ 330

(Zaumanis et al., 2014a) (Xiao et al., 2019) (Xiao et al., 2019)

4298

(Ughwumiakpor et al., 2017)

124

(IERE, 2009)

0

-

0

-

275

(Zaumanis et al., 2014a)

22

(Zaumanis et al., 2014a)

Source of data

Source of data

Table 12. The amounts of emissions produced by asphalt concrete materials and operations. Materials and process Aggregate production RAP Binder production CRM production Waste engine oil HMA operation

CH4 (gr/Ton) 0.0004 0 23 7.13 0 0.005

VOC (gr/Ton) 0.02 0 12.8 2.24 0 0.004

7

NOx (gr/Ton) 11.7 0 30 3.93 0 45.9

CO (gr/Ton) 1.4 0 23.6 4.88 0 3.8

SO2 (gr/Ton) 0.7 0 30 5.04 0 38.4

PM10 (gr/Ton) 0.4 0 6.2 1.23 0 2.9

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Table 13. The amounts of pollutions emitted by examined asphalt mixtures. Pollution Mixture Type

CH4 (gr/Ton)

VOC (gr/Ton)

Nox (gr/Ton)

CO (gr/Ton)

SO2 (gr/Ton)

PM10 (gr/Ton)

virgin

1.17

0.67

58.52

6.32

40.58

3.59

R30

0.79

0.45

54.83

5.55

39.90

3.38

R30-CRM-x

0.74

0.42

54.75

5.49

39.81

3.37

R30-CRM-x-WEO

0.78

0.44

54.77

5.53

39.86

3.38

R60

0.58

0.33

51.21

4.94

39.42

3.21

R60-CRM-x

0.54

0.31

51.15

4.89

39.36

3.20

R60-CRM-x-WEO

0.47

0.27

51.06

4.82

39.27

3.18

R100

0.17

0.09

46.11

3.97

38.61

2.94

R100-CRM-x-WEO

0.03

0.02

45.94

3.83

38.44

2.91

Table 14. The unit price of materials and operations for producing asphalt concrete. Materials and process Aggregate production RAP processing Binder production Crumb-rubber production Waste engine oil HMA operation

Unit price (USD ($)/Ton)

19.8 3.3 704 420 145 12

Source of data (Zaumanis et al., 2014a) (Zaumanis et al., 2014a) (Zaumanis et al., 2014a) (Liu et al., 2009) (Ssempebwa and Carpenter, 2009) (Yang et al., 2015)

8