Texture and Skid Resistance of Asphalt Concrete Surface Course Incorporating Geopolymer Artificial Aggregates

Skid resistance is required to prevent vehicle wheels from slipping on a road surface. The skid resistance is influenced by surface texture of the road, which is a function of aggregate properties and grading characteristics. This study aimed to examine the effect of using artificial aggregates on the texture depth and the skid resistance of two asphalt concrete surface course (ACSC) mixtures (dense and open graded). The artificial aggregate, which was made from a mixture of a locally sourced fly ash geopolymer paste and an alkaline activator, was used to partially substituting the coarse aggregate in these ACSC mixtures. ACSC slab samples, without and with 25% artificial aggregate, were produced in laboratory. The texture depth and skid resistance characteristics were subsequently determined. This study found that the differences in texture depth and skid resistance of the two ACSC mixtures were contributed by the difference in gradation of the mixtures and the properties of the coarse aggregate in the mixtures. The ACSC mixture containing 100% natural coarse aggregate (crushed stone) has a deeper and rougher texture depth than those containing 25% rounded artificial aggregate. Post-wheel track loading, the texture depth and skid resistance of open graded ACSC were found to be higher than those of dense graded ACSC. These trends were consistent regardless the type of aggregates used in these ACSC samples. Overall, all tested samples showed skid resistance values meeting the requirements for heavily trafficked roads in urban areas where the traffic speed does not exceed 95 km/h.