Multi-criteria optimization of aggregate gradation based on thermal, surface, and mechanical properties of the asphalt solar collector

The aggregate gradation of asphalt concrete for a road pavement is a critical element since it influences its strength and mechanical properties, and also has a major role on the thermal properties. An experimental study was set up to develop a multi-criteria optimization of AC12 dense-graded asphalt mixtures designed for asphalt solar collector layers according to the Bailey method (fine, middle, or coarse gradation). Samples were tested in terms of thermal potential, surface properties, and mechanical performance. It was found that a coarser gradation increased the heat concentration within the asphalt (more efficient mixture for asphalt solar collector), thanks to lower specific surface area, thicker asphalt films, and fewer interconnected internal voids. The surface and mechanical performance of all asphalt systems matched the common technical prescription limits for surface road layers. Overall, the multi-criteria evaluation was effective in optimizing the characteristics of the solar collector asphalt concrete.