Pavement Surface Mixture, Texture, and Skid Resistance: A Factorial Analysis

Skidding on wet pavements contributes to a substantial portion of highway crashes. The resistance to skidding however depends on the microtexture and macrotexture available on pavement surfaces. Several past studies have focused this aspect but with inadequate or inconsistent conclusions. The uniqueness of this study is that surface texture performance has been evaluated controlling the variability in aggregate mineralogy, environmental condition, construction and service. Portland cement concrete (PCC) specimens were prepared from a single mixture to evaluate the true effect of various surface textures on friction properties. Asphalt concrete (AC) surfaces with the same construction record were tested to examine the true effect of mix properties on surface texture and friction. Pavement surface texture was measured using the sand patch method and Automated Road Analyzer (ARAN) while the skid resistance was measured using the British Pendulum and skid trailer. Analysis has shown that a Mean Texture Depth (MTD) of about 1.8 mm is the optimum macrotexture for maximum surface friction on textured concrete surfaces. Exposed aggregate concrete may not be a preferred texture because of the benefit of sand microtexture is lost with washing out of surface mortar. AC surfaces with complex macrotexture have shown to perform differently from PCC surfaces with simple macrotexture pattern. The hypothesis that British Pendulum Number (BPN) is dependent only on surface microtexture and represents low speed friction has appeared to be invalid. The skid number-speed gradient is not something universal but varies from mix to mix. Several statistically significant models have also been developed correlating the skid resistance with the asphalt mix grading composition and surface macrotexture and with concrete surface macrotexture.