Influence of Aggregate Type and Gradation on Rolling Resistance and Functional Performance of Warm Mix Asphalt

Reducing the environmental impact of road transport requires pavements that contribute to lower fuel consumption of vehicles and greenhouse gas emissions throughout their life cycle. Rolling resistance plays a key role in this context, while warm mix asphalt (WMA) technologies offer additional benefits by reducing energy use and emissions during production and construction. This study investigates the combined influence of aggregate type and aggregate gradation on the rolling resistance and functional performance of WMA wearing course mixtures. Ten laboratory-produced mixtures were designed, including dense-graded asphalt concrete (AC 11 VS) and stone mastic asphalt (SMA 8 S) with granite or dolomite aggregates, produced at reduced temperatures using a chemical WMA additive and polymer-modified bitumen PMB 45/80-65. Rolling resistance was evaluated using a laboratory energy loss method with two different tyres, along with assessments of volumetric properties, moisture resistance, surface macrotexture, and resistance to scuffing. The results indicate that aggregate gradation is the primary factor governing rolling resistance, and dense-graded mixtures exhibit lower energy loss due to their smoother surface texture. The aggregate type showed a secondary but consistent effect, with granite mixtures generally demonstrating slightly lower rolling resistance and improved resistance to surface degradation. In general, the findings confirm that WMA technologies can be effectively integrated into low-rolling-resistance asphalt mixtures, achieving reduced rolling resistance without compromising durability and thus supporting energy-efficient and sustainable pavement solutions.