Degradation Prediction Model for Friction of Road Pavements with Natural Aggregates and Steel Slags

Steel production wastes (steel slags) are used more often in asphalt concrete pavements as a valuable replacement for natural aggregates, which are becoming increasingly rare. In this paper authors investigate the polishing characteristics of aggregates, and in particular of steel slags, used in bituminous road surfacing, are a major factor in determining the resistance to skidding. The main purpose of the study is the identification of a suitable degradation model, based on friction indicators, in the laboratory, as well as the comparison of in-situ pavement skid resistance with the cumulative number of passing vehicles over the years. The model predicts the expected resistance to skidding of the road surface based on the knowledge of the polished stone value (PSV) of the aggregates and the expected traffic on the road. In this study, several types of aggregates were compared: steel slag, limestone, limestone and slag mixture, diabase, Criggion stone and basalt. Using a standard PSV test, it was found that the aggregates did not reach the lower value of skid resistance (equilibrium value). The analysis of the British Portable Number (BPN) data versus polishing time allowed to empirically derive a regression model for each investigated aggregate. Hence, it appears possible to define both an investigatory level and threshold level to predict the actual residual life of the pavement from the examination of skid resistance.