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Aging of asphalt binder is one of the major causes of pavement distresses such as fatigue and thermal cracking. Many laboratory aging methods, namely rotational thin film oven (RTFO) with pressure aging vessel (PAV), loose mix aging and compacted mix aging, are widely practiced to test the durability of polymer-modified binder (PMB). In this investigation, binder aging (RTFO + PAV) with three PAV durations (i.e., normal 20 h (1C-PAV), extended 40 h (2C-PAV) and 60 h (3C-PAV)), extracted binder from long-term-aged (LTA) loose mix (LMAB; 85 °C, 8 days) and LTA compacted mix (CMAB; 85 °C, 5 days) were studied. Chemical analysis of LTA binders was conducted using Fourier transform infrared spectroscopy (FTIR) test, and rheological response was evaluated using dynamic viscosity, high-temperature performance grade, Superpave rutting factor and multiple stress creep and recovery (MSCR) tests. Fatigue performance of the aged binders was evaluated using linear amplitude sweep (LAS) test and binder yield energy test (BYET). FTIR results suggested that the stiffness of PAV-aged binders is predominantly due to the development of carbonyl compounds during aging, whereas the stiffening effect of mix aging is a combination of formation of carbonyl and sulfoxide compounds and polymer degradation. Findings of this investigation suggest that the present MSCR testing procedure is unable to detect polymer degradation in LTA PMB and BYET-elastic recovery parameter is a better tool. According to LAS and BYET results, 20 h of PAV aging may overestimate fatigue performance of SBS–PMB; therefore, aging of asphalt mix may be a more practical approach. [ABSTRACT FROM AUTHOR]

Long-term aging of asphalt binder plays a major role in fatigue cracking resistance of asphalt mixes. With the use of polymer-modified binder (PMB) with different polymer concentrations, aging susceptibility of asphalt mixes becomes an interesting area to explore. This study evaluated four types of asphalt mixes prepared with PMB, subjected to compacted mix aging (CMA) (85°C, 5 days) and loose mix aging (LMA) (85°C, 8 days). The aged asphalt mixes were tested for their resistance to cracking using the indirect tensile asphalt cracking test (IDEAL-CT). Furthermore, aged binders were extracted from long-term-aged loose and compacted mixes, and their fatigue resistance was examined using the Superpave fatigue factor (|G*|·sinδ), linear amplitude sweep (LAS) test, and binder yield energy test (BYET) parameters. The results indicated that both asphalt binder and mixes exhibit better cracking resistance in CMA conditions compared to LMA conditions. Mixes prepared using PMB with higher polymer content performed better in cracking resistance and were less sensitive to aging. Furthermore, to evaluate the effect of rheology of aged binder on fatigue cracking resistance of mixes, binder fatigue parameters were correlated to cracking index (CTindex) and postpeak slope (|m75|) of mixtures. Other than the yield energy parameter of BYET, a good correlation was observed between binder fatigue and mix fatigue parameters. Outcomes of this study will potentially help to understand the relationship between mixture cracking parameter and standard binder fatigue parameters and their aging sensitivity. [ABSTRACT FROM AUTHOR]

This study focused on evaluating the rutting performance of three different highly polymer-modified asphalt (HiMA) binders (i.e., O, T and B) using binder-based [i.e., multiple stress creep recovery (MSCR) and force ductility (FD)] and mix-based [flow number (FN) and Hamburg wheel tracking test (HWTT)] rutting performance tests. The binder-based rutting indicators were compared with mix rutting performance to determine a parameter that can help in the correct prediction of HiMA rutting resistance. In addition, the study looked into application of a simple performance test, the indirect rutting tolerance index (IDEAL-RT), for HiMA mix rutting prediction. The MSCR test revealed different rankings of recovery at 0.1- and 3.2-kPa stress levels. Moreover, the T and B binders did not satisfy the stress sensitivity criteria (Jnr_difference) of Max 75%. The force ductility tests revealed that the peak force observed for polymer network phase in HiMA was significantly higher than base binder stiffness, which is in contrast with force distribution in polymer-modified binders (PMBs). The mix rutting resistance ranking (O>T>B) was similar in all the tests (i.e., FN, HWTT, and IDEAL-RT). Although IDEAL-RT can be used to compare the rutting resistances of HiMA mixes, detailed future work is required to establish its acceptability in comparing various types of mixes and the minimum requirements of RTIndex. The comparison between binder and mix rutting indicators demonstrated that MSCR testing on binder at stress levels of 6.4 kPa and higher can be used to predict the rutting resistance of HiMA binders. Parameters like slope and cohesion energy and a newly introduced parameter—work done for polymer activation (WPA)—from FD tests can be used to determine the polymeric phase dominance in HiMA binders. Overall, this study provides pavement stakeholders with a framework for rightly predicting the rutting resistance and polymeric phase dominance of HiMA binders and mixes using MSCR, FD, and IDEAL-RT tests. [ABSTRACT FROM AUTHOR]

• Recycling of simulated Polymerized RAP produced using standard laboratory aging techniques. • Mix aging is better to simulate RAP from SBS PMB with 3 to 4% SBS. • Standard aging methods have distinct impact on performance of aged recycled PMB. Researchers have mostly used three artificial aging techniques, namely pressure aging vessel (PAV) binder aging, compacted mix aging (CMA), and loose mix aging (LMA) to simulate recycled asphalt pavement (RAP) binder in the laboratory. RAP binder (RAPB) simulated using different techniques will differ in characteristics and may affect the performance of the base binder differently. Which may affect the parameters used for blending and recycling, such as the selection of base binder, rejuvenator dosage, etc. Therefore, in this study, three RAP binders, namely RAPB-P, RAPB-C, and RAPB-L, were simulated from a polymer modified binder (PMB) with 3.5% SBS content, using PAV aging (100 °C, 20 hrs, 2.1 MPa), CMA (85 °C, 5 days) and LMA (85 °C, 8 days), respectively. These polymerized RAPBs were added to an unmodified binder (AC 30) at three proportions: 15 %, 25 %, and 40 %. These RAPB and AC 30 blends were characterized in terms of their dynamic viscosity, mixing and compaction temperature, and high temperature performance grade (PG). Superpave rutting factor (|G*|/sin δ) and multiple stress creep and recovery (MSCR) test parameters were used to evaluate the rutting performance of the RAPB blended AC 30 binders. Further, resistance to yielding and elastic recovery values were evaluated using the binder yield energy test (BYET). The test results suggested that all three RAP binders affect the performance of the AC 30 binder differently, which was also confirmed by statistical analysis using one-way ANOVA. From MSCR and BYET test results, it may be stated that RAP binder simulated from standard PAV aging may mislead in predicting the high and intermediate temperature performance of AC 30 binder with RAPB. Overall, the present study is helpful for asphalt researchers and practitioners to understand how the selection of different defined aging strategies affects the performance of aged recycled PMB with unmodified base binder. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) is a nanomaterial that is characterized by a two-dimensional, atomically thin, honey-combed lattice. Studies over the years have indicated potential applications of GO for improving performance characteristics of asphalt binder. This study attempts to explore the impact of GO on various chemical and rheological characteristics of unmodified asphalt binder (AC30). GO was added to AC30 over varying dosages of 1%, 2%, and 3% by weight. Carbon (C), hydrogen (H), and nitrogen (N) determinations and Fourier-transform infrared (FTIR) spectroscopy aided in understanding the chemical interaction of GO with AC30. Further, the effect of GO on dynamic viscosity was also evaluated. Rutting performance of GO-modified AC30 was studied using the multiple stress creep recovery (MSCR) test, whereas fatigue performance was evaluated based on the linear amplitude sweep (LAS) test. Additionally, yield energy GO-modified AC30 was comprehended using the binder yield energy test (BYET). CHN determination and FTIR spectroscopy indicated that modification of GO is mostly physical in nature. An improvement in aging resistivity was observed due to incorporation of GO. GO was observed to increase dynamic viscosity. Improvement in both rutting and fatigue performance of AC30 was observed but different optimum dosages of GO were obtained: 1% for maximum rutting performance and 2% for maximum fatigue performance. Enhancement in yield energy and recovery potential was also observed. [ABSTRACT FROM AUTHOR]