Influence of aggregate minerals hardness and quartz content on long-term pavement friction and wear: An experimental analysis

This study investigates the factors influencing the long-term friction performance of pavement aggregates, focusing on the roles of Average Hardness (AH), Contrast Hardness (CH), and the selection of minerals in the Aggregate Hardness Parameter (AHP). Through experimental analysis, we explored how the mineralogical composition of aggregates, particularly the presence of quartz, affects their friction retention under traffic-induced polishing. Our findings show that while AH provides useful insights, it does not fully predict long-term friction. In contrast, CH, which accounts for differential polishing between hard and soft minerals, plays a crucial role in maintaining surface texture and friction. Aggregates with a well-adjusted mix of hard and soft minerals, especially those with optimal CH at intermediate quartz content levels, exhibited superior friction retention over time. This study highlights the importance of considering both AH and CH, as well as the significance of minerals constituting more than 5 % of the aggregate content, in predicting and enhancing the long-term frictional properties of pavement materials.