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The Comparative Evaluation of Vacuum Tower Bottom Modification on the Asphalt Pavement Performance
The paper presents various investigations conducted for evaluation of the performance of polymer combined Vacuum Tower Bottom (VTB) modified asphalt mixes by comparison with different modified mixes in the laboratory scale. In order to verify the possibility of polymer combined VTB as a modifier in the asphalt binder, one base unmodified binder and two different types of modified asphalt binders well known for their good performance in the field were compared in the laboratory scale by rheological performance tests. Frequency Sweep Test (FST) and Multi Stressed Creep and Recovery (MSCR) test with DSR (Dynamic Shear Rheometer) were performed and confirmed its good performance. Secondly, various performance tests were adopted for various modified asphalt mixtures with same aggregate gradation and asphalt binder content. As to evaluate the overall performance, crack resistance and durability of dense graded mixtures, Dynamic modulus tests, Semi Circular Bending (SCB) tests and Cantabro tests were conducted for different types of mixes, respectively. Variance tests and analysis concluded several results. In the case of binder, the polymer combined VTB modifier is the primary affecting factor in performance upgrade when comparing with other binder types including base binder. The modified effects on mixtures were clearly shown in all performance tests although performance ranking out of various test types were different. Dynamic modulus are higher at low temperature and high reduced frequency while smaller modification effects in high temperature and lower reduced frequency. According to SCB test results, fracture resistance could be better than other mix types while durability of them are relatively lower. It can be concluded that polymer base VTB modifier can be act as a good modifier with increasing stiffness and fracture energy from test results. However, there are a couple of concerns remained in terms of performance verification of modifier. Therefore it is required to conduct performance simulation with MEPDG and field verification test and monitoring performance.
