Research On Application Technology For BRA Modified Asphalt Mixture

With it’s excellent pavement performance and simple construction techniques, Indonesian Buton Rock Asphalt (BRA) has received more and more attention. But due to the lack of technical regulations on the current specifications in China, the popularization and application of BRA has been limited in a certain extent. For this reason, combining with the test section engineering of BRA modified asphalt pavement in Fengda Expressway of Hunan Province, this thesis researches on the application technology of BRA modified asphalt mixture.1) According to the practice of backing project, the design scheme was put forward that the top and middle surface layer of asphalt pavement in the test section use the BRA modified asphalt mixtures. For this purpose, referring to the existing successful experiences, the thesis designed the target mix ratios for the top surface layer BAC-13C and the middle surface layer BAC-20C under 5 different kinds of BRA mixing amount from 0% to 5%, respectively. The results show that there are the good linear correlations between the optimum asphalt-aggregate ratios and the BRA mixing amounts for the BRA modified asphalt mixtures. As the BRA mixing amount increases, the optimum asphalt-aggregate of base asphalt gradually decreases, and the mixing amount of mineral powder also gradually decreases. It shows that the BRA can efficiently replace the part of base asphalt and mineral powder.2) The testing of pavement performances was respectively carried out for the target mix rations of BRA modified asphalt mixture under various BRA mixing amounts to compare with the pavement performances of ordinary asphalt mixture. The results show that the high temperature stability and water stability of asphalt mixtures can be significantly improved with BRA added, but the low-temperature performance is reduced. So the two reasonable BRA mixing amounts of 3% and 4% have been determined.3) According to the design results of target mix ratio, the production mix ratio design and the pavement performance testing were respectively carried out for the BAC-13C and BAC-20C under the two proper kinds of BRA mixing amount to compare with the SBS modified asphalt mixture in the main line. All the results obtained the experiments meet the specification requirements, and the BRA modified asphalt mixture is obviously better than the SBS modified asphalt mixture in high temperature stability and water stability, but below in low temperature stability. Based on the test results and relevant references, the thesis proposed the key techniques and quality control method on BRA modified asphalt pavement construction. At the same time, the construction of test section was strictly controlled, and the things such as field core drilling, indoor sample testing, texture depth testing, infiltration testing, and field observing were carried out. The results show that the asphalt-aggregate ratio in mixing plant and the homogeneity of mixture during construction got well controlled, the construction process is well organized, and the compaction effect of mixture is good.4) Through the comparisons of BRA with SBS from material costs, additional costs of production, maintenance and repair costs and the social benefits, BRA has more economical and a broad application prospect.In summery, the proposed application technology of BRA modified asphalt mixture in the thesis is reasonably practicable. It can be provided the reference for the further application and promotion of BRA modified asphalt mixture.