Aggregate Microtexture: Profile Measurement and Related Frictional Levels
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1981-10-01
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Edition:Staff Study
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Abstract:Reduction of skidding accidents is an ongoing objective of the highway community. Since skid resistance depends, in part, on the frictional characteristics of the pavements surface, improvements in pavement friction are constantly sought. In order to have adequate wet-weather friction, a pavement must have surface relief or texture. This texture may be divided into two size ranges: macrotexture, those features over 0.5mm in size; and microtexture, those features less than 0.5mm in size. In this study microtextural profiles were measured using an optical image analysis system. The profiles were characterized by three parameters: average asperity (peak) height, average asperity density (peaks per unit length of profile), average asperity shape factor (peak height to width ratio). These measurements were correlated with test results (polish values or PVs) using the British Pendulum Tester, which measures the friction of a pavement surface mainly due to microtexture. The resulting correlation coefficients indicate that the shape factor measurement correlates the best with the British Pendulum Tester. Optimal (highest corresponding PVs) asperity shape factor values appear to be in the range of 0.16-0.20. Aggregate types measured included both natural and synthetic material, as well as natural aggregate treated with an impregnant.
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Content Notes:This staff study done by the Paving and Structural Materials Group (HRS-22) is a work unit of FCP Project 4G, "Substitute and improved Materials to Effect Materials and Energy Conservation in Highways"
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