Evaluating Frictional Characteristics of Typical Wearing Course Mixtures in Louisiana

Abstract

Abstract In this study, the frictional characteristics of a number of Louisiana wearing course mixtures were evaluated through a suite of laboratory tests. Aggregates of different levels of micro-textures were used in the mix design. Asphalt concrete slab samples were prepared using a kneading compactor and were accelerated polished using a three-wheel polishing device developed by the National Center of Asphalt Technology for simulating the traffic-polishing effect on the surface texture of the pavement. After different numbers of polishing cycles, the frictional characteristics of asphalt concrete slabs were evaluated using a dynamic friction tester (DFT) and a circular texture meter (CTM). A comprehensive statistical analysis was conducted to investigate the effects of aggregate type and mix type on the frictional characteristics of the asphalt concrete mixtures. The international friction index F(60) values (calculated from the DFT and the CTM test results) were used to characterize the overall frictional performance of the asphalt concrete mixtures considered. The experimental results showed that aggregates with higher levels of micro-texture generally performed significantly better than those with lower levels of micro-texture in the DFT test. The open grade friction course and stone matrix asphalt showed better macro-textures than the Superpave mixtures in the CTM tests. A statistical grouping based on the terminal F(60) values of different mixtures showed that it is possible to achieve the same level of F(60) using different combinations of mix and aggregate types. This study demonstrates that blending low- and high-friction aggregates together can possibly produce an asphalt mixture with adequate field skid resistance.