Studying the effect of contaminated asphalt pavement surfaces on skid resistance

Skid resistance and road conditions are common road safety indicators; therefore, providing adequate skid resistance enhances road safety. The main concern of evaluating pavement friction is in the wet conditions and the presence of surface contaminants. Thus, it is important to find proper methods for measuring the skid resistance of the pavement surface. Rapid maintenance (removing surface contaminants) plays a major role in restoring surface friction and enhancing road safety. This research aims to evaluate the skid resistance of various types of flexible pavement mixtures at different ages subjected to different contaminants. It also studies the effect of surface maintenance on skid resistance using portable skid resistance testers (the British Pendulum Tester, BPT and sand patch). Three types of asphalt mixes were evaluated; the first was a dense-graded mixture (Control Mix), the second was a dense-graded mixture containing Reclaimed Asphalt Pavement materials (RAP Mix) and the third was an open-graded asphalt mixture (Open-Graded Mix). The selected contaminants were water, lube oil, and sand (sand dust). Laboratory tests were performed on all mixes determining British Pendulum Number (BPN) values during the testing period (75 days). The results showed that the reduction in BPN values for water contaminant was slightly lesser than that of sand and oil during the testing period. For all contaminants, the open-graded mix has the highest values of BPN compared to the other two mixes. Always, the highest contaminant effect was observed in the case of oil compared to water and sand. Also, it was observed that the BPN values were affected and enhanced by conducting the surface maintenance. The BPN values (before and after maintenance) changed by aging the pavement surface. The values of BPN decreased with an increase in the testing period due to aging effect. Finally, field measurements were conducted to verify the BPN values measured in laboratory and field for control and Rap mixes for two constructed sections. Also, sand patch test was carried out to identify mean texture depth (MTD) for the two mixes. The results demonstrated that a high correlation between BPN values for laboratory and field was found for the two sections. The value of MTD for the RAP mix was higher than the value of the control mix.