Evaluation and design of fiber-reinforced asphalt mixtures

This paper investigated the volumetric and mechanical properties, and design method of fiber-reinforced asphalt mixtures. Four different fiber were used: polyester, polyacrylonitrile, lignin, and asbestos fibers. Marshall tests were performed to measure the volumetric and mechanical properties of asphalt mixtures. Performance tests were also conducted to examine moisture susceptibility and dynamic stability. Results show that the optimum asphalt content, air void, void in mineral aggregate and Marshall stability increase, while bulk specific gravity decreases after adding fibers into asphalt mixtures. Optimum asphalt content, Marshall stability, and dynamic stability increase initially and then decrease with increasing fiber content. It also shows that the polyester and polyacrylonitrile fibers have higher stability due to their higher networking effect, while the lignin and asbestos fibers result in higher optimum asphalt content and VFA (asphalt filled in the voids of mineral aggregates) due to their higher absorption of asphalts. A design procedure for fiber-reinforced asphalt mixture is proposed, which elects the fiber type based on the characteristics of both fiber and asphalt mixture, designs the optimum asphalt content following the Marshall method, and then determines the optimum fiber content in terms of performance test results. Based on the test results, a fiber content of 0.35% by mass of mixture is recommended for the polyester fiber used in this study.