The Effect Of Surface Texture On Skid Resistance Of Asphalt Pavements

Skid resistance is such an important characteristic property of a pavement, which is to be considered in this era of great concern about road traffic safety, accidents, and injuries, and also when Hot Mix Asphalt (HMA) is to be designed. As roads and road networks are inevitable means of transport ever since, Skid Resistance, today, is one of the most noteworthy chapters of pavement engineering. It is due to the fact that there is a high correlation between low skid resistance (especially in wet weather conditions) and the accident rates. It has been shown, that friction at the interface of the vehicle tire and the pavement surface play a significant role in reducing crashes (Hall et al., 2009), and that, most of the skidrelated accidents and injuries occur when the road surface is wet (Flintsch et al., 2012). So, it can be said that the pavement surfaces with low skid resistance have had much more accident rates and casualties when compared with the pavement surfaces with high skid resistance. Studies by Kamel and Musgrove (1981) revealed that some 54 percent reduction of accidents in wet weather and about 29 percent reduction on total were possible when a pavement of high skid resistance was used. This fact was seconded by Masad et al. (2007). It is also known from the studies, that the skid resistance of a pavement surface is associated with two main characteristic properties, and they are the microtexture and the macrotexture of the pavement. Briefly, it can be said that microtexture depends mainly on the aggregate shape, its characteristics, mineralogy, and the macrotexture is dependent on mix properties, aggregate gradation, etc. (Masad et al., 2007). The Macrotexture of the pavement surface is held as one of the prominent contributory Abstract: One of the most important factors contributing to road traffic accidents in today’s busy world is lack of adequate skid resistance on roads. Adequate friction at road-tyre interface reduces skidding in both wet and dry weather conditions. As typical maintenance policies are costly and disruptive, the situation cries out to construct pavements sufficiently skid resistant in the first place. This thesis analyses the influence of Mean Texture Depth (MTD), aggregate size, spacing between aggregates (edge-to-edge), on Skid Resistance. Finally, the effect of friction on Braking Distance was investigated. Additionally, the influence of varying void contents is considered. British Pendulum Test and Sand Patch Test were performed to account for micro and macrotexture of the samples respectively. The research used asphalt concrete slabs manufactured in the laboratory with varying void content and cores from a certified engineering company. The results are presented and analyzed. In most of the cases, the cores produced justifiable results, where Skid Resistance in terms of both MTD and friction coefficient decreased with increasing spacing (edge-to-edge) and decreasing aggregate size. But, the results obtained in some cases while studying the slabs were not as expected. Nevertheless, through this study, economically and technically, the optimal choice of asphalt mix, gradations, aggregate size, spacing and MTD could clearly be recommended considering the UK specifications for minimum skid resistance on roads.