Comprehensive Evaluation of Fatigue Performance of Modified Asphalt Mixtures in Different Fatigue Tests

The four-point bending beam fatigue test (4PB), two-point bending trapezoidal beam fatigue test (Trapezoidal Beam), and Overlay Tester (OT) are used to evaluate the fatigue performance of six kinds of asphalt mixtures that are widely used in engineering, and newly developed ones. The result shows that, in all three kinds of fatigue tests, the fatigue performances of the 6% SBS (styrene-butadiene-styrene block copolymer) modified asphalt mixture is the best, and those of the 10% WPE (waxed polyethylene) + 3% SBS, 4% SBS + 0.4% PA610, and 4% SBS modified asphalt mixture are good. The fatigue performances of the warm modified mixing agent and the base asphalt mixture are the worst. An increase in SBS content can effectively improve the fatigue performance of the asphalt mixture. The fatigue performance of the SBS-modified asphalt mixture can be improved by the addition of WPE and PA610. In different tests, the ranking of fatigue performance of the asphalt mixture is similar, and the specific ranking is slightly different. The three different fatigue tests can be used simultaneously to obtain a more comprehensive and objective evaluation in the R&D process for a new modified asphalt. The three fatigue tests process shows that more precise forming and cutting technology is needed, as the strain range used in the 4PB test is very wide, and the number of samples used in each group is small. The preparation of the Trapezoidal Beam test samples is complex; the amount of test data is huge and has high precision, which is suitable for scientific research instead of a field laboratory, and the strain range of the test is moderate in the three methods. The strain range of the OT test is the narrowest; the test specimen is relatively simple to prepare, and the fatigue performance of a specific modified asphalt mixture can be obtained quickly in a simple laboratory

Investigation of the bonding properties of bitumen using a novel modified binder bond strength test

The binder bond strength (BBS) test can directly quantify the bonding of bitumen-stone joints. However, the index "bond strength" used in this method cannot provide a clear distinction when evaluating the performance of various bitumen, and some results do not correspond to the field feedback related to the bonding performance. This study introduces a novel modified BBS test using the universal testing machine (UTM). The results of the standard BBS test and the BBS-UTM test on six unmodified bitumens and a styrene-butadiene-styrene modified bitumen (SBSMB) are compared, with the Cantabro loss test to validate the accuracy of the BBS-UTM test. The results show that the "bond energy" can be considered the critical indicator for characterising the bonding performance of different binders. The force-displacement curve in the BBS-UTM test is analysed and provides a mechanistic explanation for the mechanical response of bitumen during pull-off. The four-component test is conducted to link the bitumen composition characteristics to its bonding performance. It is found that bitumen adhesion is correlated to the content of asphaltenes. A higher saturates content shows more contribution of tenacity in the total bond energy, and an excessively high ratio of asphaltenes to resins may result in low bond energy

Critical considerations and effective assessment of extraction and recovery processes of RAP

With the increasing shortage of resources, the reuse of recycled asphalt pavements (RAP) in pavement engineering is considered as a sustainable technology. Challenges posed by common extraction and recovery methods may result in misjudgment of asphalt pavement performance. In this study, we investigate the optimization of extraction and recovery processes in recycled asphalt pavement (RAP) recycling, aiming to promote sustainable development within the pavement engineering sector. We prepared eleven asphalt samples to simulate common extraction and recovery scenarios, using virgin SBS-modified asphalt as a reference. Employing Fourier Transform Infrared (FTIR) analysis, thermogravimetric analysis (TGA), and Dynamic Shear Rheometer (DSR) testing, we assessed the samples' rheological and chemical properties. We pointed out three common but easily overlooked problems in the extraction and recovery process, namely residual mineral powder, residual trichloroethylene, and incomplete extraction. Residual mineral powder and trichloroethylene greatly influence extraction recovery accuracy; high-speed centrifugation effectively addresses trichloroethylene, but completely removing mineral powder remains challenging. Accurate evaluation of residual substances in recycled asphalt is achievable through FTIR, TGA, and rheological tests, providing valuable insights for material selection and processing. Additionally, it is crucial to fully recover the binder from RAP for precise performance evaluation, as the binder's interior exhibits lower aging levels compared to the surface. This aging heterogeneity should be considered when assessing RAP performance and developing effective rehabilitation strategies. Our findings hold significant implications for enhancing the efficiency and effectiveness of extraction and recovery processes in RAP recycling, ultimately contributing to sustainable development in pavement engineering

Critical considerations and effective assessment of extraction and recovery processes of RAP

With the increasing shortage of resources, the reuse of recycled asphalt pavements (RAP) in pavement engineering is considered as a sustainable technology. Challenges posed by common extraction and recovery methods may result in misjudgment of asphalt pavement performance. In this study, we investigate the optimization of extraction and recovery processes in recycled asphalt pavement (RAP) recycling, aiming to promote sustainable development within the pavement engineering sector. We prepared eleven asphalt samples to simulate common extraction and recovery scenarios, using virgin SBS-modified asphalt as a reference. Employing Fourier Transform Infrared (FTIR) analysis, thermogravimetric analysis (TGA), and Dynamic Shear Rheometer (DSR) testing, we assessed the samples' rheological and chemical properties. We pointed out three common but easily overlooked problems in the extraction and recovery process, namely residual mineral powder, residual trichloroethylene, and incomplete extraction. Residual mineral powder and trichloroethylene greatly influence extraction recovery accuracy; high-speed centrifugation effectively addresses trichloroethylene, but completely removing mineral powder remains challenging. Accurate evaluation of residual substances in recycled asphalt is achievable through FTIR, TGA, and rheological tests, providing valuable insights for material selection and processing. Additionally, it is crucial to fully recover the binder from RAP for precise performance evaluation, as the binder's interior exhibits lower aging levels compared to the surface. This aging heterogeneity should be considered when assessing RAP performance and developing effective rehabilitation strategies. Our findings hold significant implications for enhancing the efficiency and effectiveness of extraction and recovery processes in RAP recycling, ultimately contributing to sustainable development in pavement engineering.Pavement Engineerin