Method for Predicting Asphalt Mixture Skid Resistance Based on Aggregate Characteristics and Gradation.

The objective of this study is to develop a method for estimating the skid resistance of an asphalt mixture based on aggregate characteristics and gradation. Asphalt mixture slabs with different combinations of aggregate sources and mixture designs were fabricated in the laboratory and their skid resistance was measured after different polishing intervals. The wheel polishing device developed by the National Center for Asphalt Technology (NCAT) was used for polishing the slabs. Frictional characteristics of eachslab were measured by the sand patch method, British Pendulum, Dynamic Friction Tester (DFT), and Circular Texture Meter (CTMeter). Aggregates werecharacterized using petrographic analysis, a number of conventional test methods, and texture analysis using the Aggregate Imaging System (AIMS) after different polishing intervals in the Micro-Deval. The aggregate gradation was described using the two-parameter cumulative Weibull distribution function. The data statistical analysis has led to the development of a model for the International Friction Index (IFI), a measure of skid resistance, of asphalt mixtures as a function of polishing cycles. The IFI modelsparameters were found to be functions of (a) initial and terminal aggregate texture measured using AIMS, (b) rate of change in aggregate texture measured using AIMS after different polishing intervals, and the (c) Weibulldistribution parameters describing aggregate gradation. This model allowsestimating the frictional characteristics of an asphalt mixture during the mixture design stage.