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Abstract: The objective of this study is to analyze the frictional properties of mineral aggregates after conducting a comprehensive experimental program. A total of 15 aggregate sources from five different regions in China were selected and tested using a specially-designed device stationed at the State Key Laboratory of Tribology in Tsinghua University. A total of 4 groups of experimental tests were performed to measure the aggregate frictional coefficients under different testing conditions. In the first group, a total of 25 tests were performed to study the impact of loading levels and rotational velocities of the rolling shafton the measured frictional coefficients. The second and third groups of tests were conducted to study the dry and wet friction at the surfaces between the aggregate specimens and the outer ring of the rolling shaftwith the milled sands pretreated. The fourth group of tests was performed to measure the dry friction at the surfaces between the aggregate specimens and the outer ring with the car tire rubber pretreated. From the experimental test results for most aggregate sources, it was observed that: 1) in the second and third groups of tests, both wet and dry frictional coefficients sharply increased at the beginning, then after their peak values the dry frictional coefficients kept constant while the wet frictional coefficients decreased smoothly over the testing time; 2) the wet frictional coefficients were lower than the dry frictional coefficients; 3) the dry frictional coefficients at the surfaces between aggregates and the milled sands were smaller than those at the surfaces between aggregates and the car tire rubber. However, the second and third observations above were not true for several individual aggregates tested.
Key words: Aggregate; Friction coefficient; Tribology; Pavement.
Introduction
The skid resistance of a road surface is one of the fundamental requirements in pavement engineering. Pavement surface friction is a measure of pavement riding safety and plays an important role in reducing wet-pavement skid accident. According to the reference [1], 2,766 people died and 222,455 people were injured on Canadian roads in 2003 from a total of 156,904 police reported crashes, while 42,643 fatalities and about 2.9 million injuries were reported in 2000 from about 6.3 million traffic crashes in the United States. Researchers [2] concluded that uncontrolled skidding due...
