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Based on the efficient resource utilization of scrap tires, pyrolysis carbon black (PCB), and pyrolysis oil of waste tire (TPO), scrap tires' products were treated using dry styrene-butadiene-styrene (SBS) polymer modification of asphalt. The products of scrap tires, PCB and TPO, were handled using dry SBS polymer modification of asphalt based on the effective resource use of scrap tires. The consequences of scrap tires, PCB and TPO, were taken using dry SBS polymer modification of asphalt based on the effective resource use of scrap tires. PCB and TPO composite effect seriously degraded. Based on this, the impact of dry SBS polymer modification on the functionality of PCB-TPO-modified asphalt and the mechanism of modification was examined. According to the investigation, the SBS polymer was evenly distributed and fully developed in the asphalt mixture, which significantly enhanced the qualities of asphalt and the asphalt mixture and performed a positive role in the internal structure of the asphalt mixture. [ABSTRACT FROM AUTHOR]

As a potential long-life pavement material, the high brittleness of epoxy asphalt prevents its application. Recycled from waste tires, crumb rubber (CR) can be used with styrene-butadiene-styrene (SBS) to prepare SBS/CR composite modified asphalt. The main objective of this paper is to conduct the material design of epoxy asphalt with SBS, CR, and core-shell rubber (CSR) to toughen the epoxy asphalt and enhance its performance. First, SBS modified epoxy asphalt and SBS/CR composite modified epoxy asphalt (CMEA) were prepared to optimize the toughening materials based on tensile tests. Subsequently, based on the optimized material, the optimal proportion was determined through the response surface method by the Design-Expert software. Third, the microscopic morphology of different epoxy asphalt was observed by laser scanning confocal microscopy (LSCM), and the changes in functional groups were tracked using Fourier transform infrared spectroscopy to reveal the toughening mechanism. Finally, the viscosity test was carried out on the optimal SBS/CR-CSR CMEA at different temperatures to determine its mixing temperature and allowable time. The results show that the SBS/CR-CSR CMEA is the best toughening method, and the optimal epoxy and CSR proportion is 37% and 12%, respectively. Its tensile strength increases by 467.11% and elongation at break increases by 68.73% compared with unmodified epoxy asphalt. The formation of interpenetrating polymer network structure between the SBS/CR network and epoxy resin network, as well as the change in the benzene ring that determines the softness and toughness, may be the main strengthening and toughening mechanisms. The suitable mixing temperature is 160°C for the optimal SBS/CR-CSR CMEA in this paper, which reduces about 20°C compared with conventional CR or SBS/CR composite modified asphalt, providing better environmental benefits. Overall, the SBS/CR-CSR CMEA presents a new solution for the promotion and application of epoxy asphalt. [ABSTRACT FROM AUTHOR]

Composite modification of an asphalt binder forms an interesting approach to enhance the properties over diverse performance regimes. Aging of asphalt binders during the production, construction, and service life of the asphalt mixtures in pavement increases its stiffness and may have a negative impact on their resistance toward fatigue and low-temperature cracking, thus generating the need to evaluate the aging behavior of a composite-modified asphalt binder. This study analyzed the aging characteristics of individual and composite asphalt binders produced with waste ethylene-propylene-diene-monomer (EPDM) rubber, derived from manufacturing units dealing with nontire automotive rubber products, and the tire pyrolysis oil (TPO) derived from the pyrolysis of scrap tires. Three different pathways were used to formulate composite-modified binders, namely, without pretreatment and with pretreatment through heat and microwave irradiation. The study focused on the evaluation of physical, rheological, chemical, and microstructural characteristics of the composite-modified binders produced in different manners after being subjected to both short-term and long-term aging. Results showed that the effect of aging was adverse on the base binder and the binder prepared with TPO alone. In contrast, the addition of EPDM rubber alone improved the binder's aging resistance. The composite-modified binder through the pretreatment yielded significantly improved performance against aging; thus, composite modification with pretreatment can be a useful approach to yield aging-resistant binders prepared by EPDM and TPO. [ABSTRACT FROM AUTHOR]

Crumb rubber (CR) from grinding waste tires has served as an asphalt modifier in asphalt pavement construction for decades. Incorporating CR in asphalt mixtures by the dry method is becoming popular with the emphasis on low carbon emissions, greenness, and sustainability. However, the poor compatibility and mechanical performance of dry-mixed asphalt rubber limit its application. This work presents the effect of practical activation treatments on the microstructure of CR and mechanical properties of the resulting asphalt binder and mixtures, aiming to modify CR surface features and improve the performance of asphalt mixtures. According to previous work, the activation treatment methods of high-temperature, preswelling, the two combinations, and microwave irradiation for CR were compared. Meanwhile, the surface morphology, chemical features, and dispersion degree of various activated CR as well as rutting resistance, low-temperature performance, and moisture stability of the resulting asphalt and asphalt mixtures were evaluated. The results indicated that selected activation methods significantly change the surface morphology and chemical features of CR, and the activated CR shows a flocculent structure with porous surface and reactivity. Preswelling with high-temperature and microwave activation for CR endows the modified asphalt with significantly improved viscoelastic properties. Preswelling with high-temperature activated CR asphalt shows better low-temperature cracking resistance. Asphalt modified with activated CR presents homogeneous and compatible states in microscopy compared with ordinary asphalt rubber. Incorporating activated CR in asphalt mixtures by the dry method is a promising technique in view of improved low-temperature cracking resistance and moisture stability. [ABSTRACT FROM AUTHOR]

Waste tire pyrolysis has the advantages of economy, environmental protection, and high energy conversion rate; however, there is little research on the application of pyrolysis carbon black (PCB), which accounts for a high percentage of pyrolysis products, in asphalt and asphalt mixtures. The objectives of this study were to investigate the effect of PCB ash on the physical properties of asphalt binders, the effect of coupling treatment on the dispersibility of PCB-modified asphalt, and the effect of mixing process on the road properties of PCB asphalt mixtures. The physical properties of co-pyrolytic carbon black (CPCB) and low-temperature vacuum pyrolytic carbon black (VPCB) blended with 70# base asphalt and styrene-butadiene-styrene (SBS)–modified asphalt (SBSMA) were evaluated. Mechanisms behind the differences in the dispersion of CPCB in asphalt were revealed. In addition, the road performance of different PCB asphalt mixtures was compared. The results indicate that the optimum admixtures of VPCB and CPCB in 70# base asphalt are recommended to be 20% and 10%–15%, respectively, and the optimum admixtures of VPCB and CPCB in SBSMA are 10%–25% and 10%–20%, respectively. Acid washing reduces the ash content of the CPCB surface, and coupling agent can promote the dispersion of CPCB in asphalt. The wet-prepared CPCB-modified asphalt mixtures showed overall better road performance than the dry-prepared ones. Dry CPCB asphalt mixtures with 50% cement instead of equal mass of mineral powder have the potential to replace the wet process. [ABSTRACT FROM AUTHOR]

Low-carbon environmental protection and reduction of pollution have become development goals for asphalt pavement. Crumb-rubber modified asphalt binder (CRAB) made from recycled scrap tires provides an economical and practical way to salvage the natural raw materials but results in carbon and toxic emissions. Warm-mix technology has been applied to recycled CRABs, forming warm-mixed crumb-rubber asphalt binders (W-CRABs) as effective and efficient green materials to reduce energy consumption and mitigate environmental pollution. In addition, the type and dosage of warm-mix additives are key factors affecting rutting and cracking pavement distress. This study aims to correlate Superpave protocol results with those of fractional viscoelastic models to estimate the high- and low-temperature properties of W-CRABs, including recycled crumb rubber, viscosity reducer (1%, 2%, 3%), and surfactant (0.4%, 0.6%, 0.8%). Bending beam rheometer and dynamic shear rheometer tests were performed to determine experimental parameters such as complex modulus, phase angle, and the ratio of creep rate to creep stiffness (m/S). The fractional derivative model (a connection composed of one spring, one linear dashpot, and two Abel dashpots in series) and the generalized fractional viscoelastic model (a combination of two spring-spot fractional elements in series) were developed to investigate viscoelasticity of W-CRABs. In conclusion, by experimental and modeling methods, this study recommends that, for northwest China with significant temperature differences, the optimal resistance to cracking and rutting can be achieved by mixing 0.6% surfactant and CRABs. [ABSTRACT FROM AUTHOR]

Waste ethylene-propylene-diene monomer (EPDM) rubber and tire pyrolytic oil (TPO) derived from waste tire pyrolysis have shown promising results for their use in asphalt binder modification. However, their incorporation has shown improvements mainly either on rutting or fatigue behavior of the resultant asphalt binders. Composite modification may be a viable option to achieve improved performance with these two materials. The aim of this study was to evaluate the rheological, morphological, and chemical properties of asphalt binders produced through both individual and composite modifications using waste EPDM rubber and TPO. For composite modification, two different blending schemes were used: (1) sequential addition of TPO and EPDM rubber to the heated base asphalt binder; and (2) premixing of TPO and EPDM rubber prior to addition to the heated base asphalt. In the latter case, before being added to the base asphalt, TPO premixed EPDM rubber was conditioned at two temperatures (25°C and 90°C) to see the effect of different conditioning temperatures in composite modification. Firstly, the conventional properties of all the binders in the unaged state were assessed, followed by the evaluation of short-term-aged binders for Superpave and Shenoy rutting parameters, frequency sweep, zero shear viscosity, multiple stress creep and recovery, and Burger's modeling. The long-term-aged binders were evaluated through the Superpave fatigue parameter, Glover-Rowe parameter, and linear amplitude sweep. Fourier transform infrared (FTIR) spectroscopy and optical microscopy were used for chemical and morphological analyses. The premixing of EPDM and TPO accompanied with conditioning at 90°C imparted a synergistic effect with improvements in both rutting and fatigue performance of binder. The improvement in performance attributes was ascribed to the preswelling of EPDM rubber with TPO, which was evident from the morphological analysis. FTIR provided evidence of chemical interaction between EPDM rubber and TPO during the conditioning and blending processes. [ABSTRACT FROM AUTHOR]

Research on waste tire pyrolysis carbon black (PCB) in bitumen mixtures indicates that it has excellent high-temperature rutting resistance; however, the degradation of low-temperature crack resistance and water stability of PCB-modified asphalt limits its wide application. Therefore, the low-temperature crack resistance and water stability of PCB-modified hot-mix asphalt (HMA) were enhanced by addition of waste chicken feather (WCF). Based on the response surface methodology (RSM), a variance analysis (ANOVA) and P-value test of the model response coefficient were carried out, and the performance prediction models of percentage air voids (VV) in bituminous mixtures, 30-min Marshall stability (MS), and 48-h MS were obtained. The interaction effects of different independent variables on response variables were analyzed. In addition, the optimal solutions of multiresponse variables obtained by the response optimizer were 0.20% PCB content, 0.36% WCF content, shearing time of 5.78 min for WCF, and 6.66% asphalt–aggregate ratio. The corresponding performance index prediction values were 4.00% VV, 12.80 kN 30-min MS, and 12.65 kN 48-h MS. The road performance test results demonstrated that incorporating WCF improved the high-temperature rutting resistance, low-temperature crack resistance, and water stability of PCB-modified hot-mix asphalt. This study provides a precise performance prediction model for adding PCB and WCF to HMA. [ABSTRACT FROM AUTHOR]

This study evaluated tire pyrolytic oil (TPO) derived from waste tire pyrolysis as a rejuvenating agent for three types of aged asphalt binders (unmodified, polymer-modified, and crumb rubber–modified). Gas chromatography–mass spectrometry (GC–MS) was performed to identify chemical compounds present in TPO. The rheological characteristics of all binders were examined through the complex viscosity–frequency profile, zero-shear viscosity, failure temperature, Black space diagrams, Cole–Cole plots, Superpave fatigue parameter, Glover–Rowe parameter, and linear amplitude sweep (LAS) tests. Mass loss was also determined for the rejuvenated binders. All binders were subjected to Fourier transform infrared (FTIR) analysis, and sulfoxide and carbonyl indices were computed. Atomic force microscopy (AFM) was conducted to study the effect of TPO on the micromorphology of the binders. The normalized Euclidean distance approach was used to rank the rejuvenated binders with respect to the proximity of their rheological and FTIR characteristics to that of the unaged binder. The use of TPO as a rejuvenating agent enabled the aged binders to achieve properties comparable to those of the unaged asphalt binder. The AFM-based rejuvenation index (RI) indicated a good potential of TPO as a rejuvenator. The results of the binder rheological parameters and the FTIR indicators investigated in the study indicated that a 9% dosage of TPO as a rejuvenating agent was the most effective. [ABSTRACT FROM AUTHOR]

The asphalt modifier formed by the miscibility of waste cooking oil and rubber is referred to as WRO. WRO modifiers prepared from waste tire crumb rubber (WTCR) and waste cooking oil (WCO) have the potential for solving the problems of segregation of rubber asphalt and the low recycling rate of waste cooking oil. The results of the Cole-Cole curve show that the WRO modifier can remarkably enhance the miscibility of WTCR and base asphalt. The Fourier transform infrared spectrometer (FTIR) tests proved that WTCR, WCO, and base asphalt were mainly physically miscible during the preparation of the WRO modifier and modified asphalt. In the process of preparing the WRO modifier and modified asphalt, the rubber undergoes devulcanization, conjugated double bond reduction, and oxidation reactions. The WRO modified asphalt presents great workability, storage stability, high-temperature elastic recovery, low-temperature crack resistance, and deformation recovery ability. In addition, the results of the multiple stress creep and recovery (MSCR) tests present that the WRO modified asphalt has desirable antirutting properties. The optimal preparation process of the WRO modifier preferred by orthogonal design is stirring 0.5 h at 260°C, and the mass ratio of WTCR and WCO is 6∶4. [ABSTRACT FROM AUTHOR]

Pyrolysis technology is receiving growing attention for managing postconsumer tire and plastic waste streams. Pyrolytic char is generated as a byproduct in the pyrolysis process and faces challenges regarding its stable and reliable reuse. The use of tire pyrolytic char (TPC) and plastic pyrolytic char (PPC) has recently gained interest in asphalt binder modification, which can be a feasible and attractive alternative for their utilization. The present study focused on a multifaceted investigation at three levels: (1) characterization of the pyrolytic chars (TPC and PPC), (2) characterization of asphalt binders modified with different dosages (0%, 5%, 10%, 15%, and 20%) of TPC and PPC focusing on conventional, rheological, microscopic, and thermochemical tests, and (3) mechanical characterization of asphalt mixtures fabricated with TPC- and PPC-modified binders in terms of rutting, moisture damage, and fatigue performance. Leachate toxicity was also evaluated to ensure that the use of TPC and PPC in asphalt mixtures is safe for the environment. Results showed that both TPC- and PPC-modified binders and mixtures showed better rutting resistance than the control binder and mixture up to 20% dosage. Fourier transform infrared (FTIR) spectroscopy showed that TPC and PPC interacted chemically with the base binder during modification. Leaching tests indicated that TPC and PPC could be safely used in asphalt mixtures for pavement construction. Comparing the fatigue and moisture damage results, it was found that the optimum performance was achieved at a 10% dosage of both TPC and PPC. This observation was consistent with fatigue tests on binders and asphalt mixtures. [ABSTRACT FROM AUTHOR]

Pyrolysis is being employed as a viable option for the disposal of different industrial and agricultural wastes, including end-of-life vehicle tires. Tire pyrolytic char (TPC), a solid fine carbonaceous material obtained as a by-product during the pyrolysis of waste tires, is gaining interest among pavement researchers for its use in asphalt binder modification. Good storage stability is essential to ensure that a modified binder retains the desired properties after its fabrication. Cross-linking agents are frequently used to enhance the storage stability of modified binders. This study characterized the storage stability performance of TPC-modified binders with and without the incorporation of cross-linking agents. Bituminous binders modified with TPC were analyzed for storage stability at multiple dosages of two widely used cross-linking agents: polyphosphoric acid (PPA) (0.5%, 1.0%, and 1.5%) and sulfur (0.15%, 0.3%, and 0.45%). In addition to softening point difference (SPD), separation indices (SIs) derived from frequency sweep, temperature sweep, and multiple stress creep and recovery (MSCR) tests were employed to characterize the storage stability. Compatibility evaluation was also done through Cole-Cole plots. Fourier transform infrared spectroscopy (FTIR) was used to study the storage stability through the changes in binder spectra. Remixing of the TPC-modified binders was also performed to assess the retrieval of homogeneity in a segregated TPC-modified binder. All the SIs were measured and compared for binder specimens before and after remixing. Binders were ranked based on the SIs, followed by sensitivity and correlation analyses of the SIs. TPC-modified binder showed a good storage stability performance with sulfur (at 0.3% optimum dosage) and PPA (at 1% optimum dosage). Remixing resulted in further enhancement in the storage stability performance of TPC-modified binders. The results of the study are quite useful considering the practical usage of TPC for a storage-stable modification of asphalt binder. [ABSTRACT FROM AUTHOR]

The crumb rubber (CR) derived from waste tires has been used widely to prepare rubberized asphalt for paving applications. However, rubberized asphalt severely suffers from poor compatibility and consequent storage instability. Therefore, a solution soaking pretreatment was used to activate the CR surface to improve the compatibility of rubberized asphalt in this study. Three different solutions—water, sodium hydroxide, and sulfuric acid—were employed. The Fourier-transform infrared spectroscopy (FTIR) spectra indicated the removal of zinc stearate from the CR surface after solution soaking. Consequent improvement of the surface hydrophilicity of CR was found from the promoted sedimentation in water and the reduced water contact angle. Dynamic dhear rheometer (DSR) test results showed that the effect of solution soaking on the rheology of rubberized asphalt was slight. However, according to the results of the segregation test and a novel drainage-based method, the solution soaking pretreatments significantly improved the compatibility of rubberized asphalt. This was reflected directly in the reduced segregation degree and promoted CR/asphalt interactions. The solution soaking pretreatment of CR had no adverse effect on the moisture susceptibility of rubberized asphalt according to the modified binder bonding strength (BBS) test results. Of the three pretreatments, sodium hydroxide performed best, followed by sulfuric acid and water. [ABSTRACT FROM AUTHOR]

The effect of ethylene vinyl acetate (EVA) on the aging properties and rheological properties of rubberized asphalt was measured in this paper to identify the optimum proportion of EVA combined with waste tire rubber (WTR) modified asphalt. Aging methods of thin-film oven test (TFOT) and pressure aging vessel test (PAV) were conducted to imitate the different degrees of the aging process. At first, frequency sweep at different temperatures was carried out to construct the construction of G* master curves, following the time-temperature superposition principle, to evaluate the aging sensitivity. The black diagram was depicted to compare the rheological behavior of different asphalt binders. The calculation of the WLF equation based on the shift factor of master curves was conducted to calculate the values and aging index of 15°C DSRFn to assess the resistance to fatigue cracking at the intermediate temperature. Then, zero shear viscosity (ZSV) and rutting factor (G*/sinδ) at 60°C were also used to calculate the aging index, because these both are measurements of resistance to rutting deformation at high temperature. Finally, the microstructure of unaged and aged asphalt binder was studied by Fourier transform infrared spectroscopy (FTIR). The relationship between rheological and chemical indexes was studied. The results show that 15%WTR+4%EVA has the best antiaging performance, and EVA can reduce the aging sensitivity of different parameters, especially in the high-temperature area. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the use of crumb rubber (CR) from waste tires and engineered additives as a rejuvenator to high reclaimed asphalt pavement (RAP) content asphalt mixtures. Six asphalt mixtures were prepared by mixing aggregate blends with four asphalt binders, an unmodified asphalt binder classified as performance grade (PG) 64-22, two polymer-modified binders classified as PG 70-22M and PG 76-22M, and a PG 76-22 crumb-rubber-modified binder. The RAP content was varied from 0-40% and crumb-rubber additives were blended with the unmodified binder by using wet and dry processes. Hot-mix asphalt (HMA) mixture testing included an evaluation of rutting susceptibility, moisture resistance, and resistance to cracking using the flow number test, the loaded-wheel tracking test, the dynamic modulus test, the modified Lottman test, the dissipated creep strain energy test, and the semi-circular bending test. Results of the experimental program indicated that the addition of the CR additives rejuvenated the blended asphalt binder for the HMA mixture with high RAP content. The use of high RAP content with crumb rubber as a rejuvenator in the preparation of HMA is expected to provide adequate moisture resistance and superior rutting resistance as compared to conventional mixtures. However, because of the hardening properties of the mix prepared with high RAP content, the fracture and cracking resistance of the produced mixture was reduced compared with polymer-modified mixes. [ABSTRACT FROM AUTHOR]