Abstract

Abstract

Research has clearly shown that as the skid resistance of a road surface decreases, the road-based transport crash rate increases. In recognizing the importance of providing safe pavement surfacings for travel during wet weather, most highway controlling authorities in developed countries have skid resistance standards. However, recent research has demonstrated that there is significant variation in performance between natural aggregates where supposedly high-quality surfacing aggregates (as measured by the Polished Stone Value Test) have not performed well or predictably over an economic asset life in areas of high demand for friction. A comparison is made between the performance of six natural aggregates (greywackes, felsic volcanic rocks and basalts) used in New Zealand as road surfacing dressing. The comparison includes surface friction test results of prepared samples that have undergone accelerated polishing using a new laboratory test method. The coefficient of friction is measured at various stages of polishing by the Dynamic Friction Tester. Scanning electron microscope (SEM) photographs show the characteristics of the microtexture of the aggregate surface before and after accelerated polishing, correlating the degree of surface polishing to the measured skid resistance performance and relating this to the aggregate mineralogy, grain size, and degree of lithification and diagenesis.

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