Evaluation of Dolomite and Related Aggregates Used in Bituminous Overlays for Indiana Pavements

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Evaluation of Dolomite and Related Aggregates Used in Bituminous Overlays for Indiana Pavements

West, Terry R. / Choi, J. C. / Bruner, D. W. / Park, H. J. / Cho, K. H.

To allow vehicles to stop in a reasonable distance, adequate friction resistance is needed to prevent pavement slipperiness. In stone-masticasphalt surfaces, friction resistance is mainly caused by the interaction between aggregates exposed at the surface and vehicle tires. Performance of aggregates is reduced with time through wear and polishing by vehicular traffic. A method to investigate aggregate performance using physical, chemical, and petrographic factors was evaluated. The objective was to develop a laboratory test for Indiana dolomite, limestone, sandstone, and gravel aggregates to predict field friction resistance and to determine causes for the range of polish resistance of these aggregates. Dolomite and slag are specified aggregates for wearing surfaces for high-traffic roads in Indiana, but some limestones and crushed gravels may prove acceptable. Gravel sources were assessed on the basis of percentages of rock types included in the gravel. Initial friction values and polished values were determined in the laboratory using the British wheel and pendulum procedures, and field values were determined with the towed friction trailer (ASTM E274-97; average friction numbers), which yielded friction number smooth (smooth tire) and friction number ribbed (ribbed tire). Correlations between parameters predict friction resistance from laboratory test data. Also polished values of 25 may be equivalent to a friction number smooth of 27.7 and friction number ribbed of 30.7. Further refinement is required to establish performance specifications for individual aggregate selection.