Evaluation of Skid Resistance Using CTM, DFT and SRT-3 Devices

Abstract

Evaluation of skid resistance could be based on both microtexture and macrotexture. It is possible to measure this parameter using CTM (Circular Track Meter) and DFT (Dynamic Friction Tester) devices. Macrotexture is characterized by the MTD (Mean Texture Depth) parameter obtained by CTM measurements. Microtexture can be estimated by the coefficient of friction DFT20 at a slip speed 20 kph using low speed friction measurement devices such as DFT. In this paper the possibility of using CTM and DFT for assessment of wearing course made from SMA (Stone Mastic Asphalt), AC (Asphalt Concrete), Slurry Seal and exposed aggregate PCC (Pavement Cement Concrete) is presented. Eleven test sections were considered. In addition, coefficient of friction μ was measured by SRT-3 device with locked wheel at test speed 30, 60 and 90 kph. Good correlation between DFT20 and μ at tested speeds was observed. It found out that SRT-3 device is more sensitive to microtexture changes in the pavement but not to macrotexture. The influence of asphalt mixture composite, texturing method, polishing resistance of coarse aggregates on skid resistance were analyzed. The measured values of the DFT and CTM devices were used to calculate the IFI numbers for each test section according to the ASTM E1960-07(2011) standard. In addition based on IFI, the coefficient of friction F(S) was calculated at various slip speeds S. Consequently, different pavements surfaces were compared in regard to slip speed S. As the result of the analysis it was found that at low speed pavements made of AC had better skid resistance than SMA and exposed aggregate PCC, while at high speeds SMA and exposed aggregate PCC had better skid resistance than AC pavements. This information is valuable for proper maintenance of existing pavements and on the stage of designing.