Optimal bitumen-aggregate ratio selection method of hot mix asphalt based on closest compaction condition

An optimal bitumen-aggregate ratio selection method for hot mix asphalt, based on aggregate closest compact condition, was introduced. According to research, high correlation within dry density, voids in mineral aggregate (VMA) and voids in coarse aggregate (VCA) versus bitumen-aggregate ratio was discovered. Dry density increases with increase of bitumen-aggregate ratio until it reaches a peak, and then decreases. VMA and VCA have the inverse trend. The advantage of the unique extreme point rule of the conic is the relationship of bitumenaggregate ratio versus dry density and that the VMA and VCA can be indicated by conic regression analysis, and the corresponding bitumenaggregate ratio can be achieved as well. In this paper, the new design method was adopted for hot mix asphalt in various gradations and the differences from the previous design method were also illustrated. The inaccurate bitumen-aggregate ratio due to previous design criterion can be avoided through setting the closest compact condition. This can also be recommended as the design criterion.