of Aggregates Gradation for High-Performing Asphalt Composites
Strategic Highway Research Program (SHRP) developed a rational volumetric mix design procedure called Superpave mix design. It requires aggregate gradations which pass through selected number of control points, and recommends to avoid a restrict zone. However, it has been reported that the effect of Superpave gradation on asphalt pavement performance has been contradictory and/or inconclusive. Also, some agencies have been experiencing difficulties to meet the new gradation requirement and to adjust the gradation in the field. In addition, gradation requirement introduced in Superpave mix design, plotted on 0.45 power chart, has not considered about aggregates structure fully. Therefore, there was a need to modify the Superpave Mix-Design and/or to develop a new procedure to design proper aggregate structure for various types of aggregates.
The present study utilized various existing methods including the Bailey method. The bailey method provides a systemic approach to determine aggregate structure considering its aggregate packing properties. After evaluating procedure of Rhode Island Department of Transportation (RIDOT), Superpave Mix Design, and Bailey method, a systemic procedure has been developed to optimize mineral aggregates for high-performing asphalt composites. It is anticipated that volumetric properties of mixture could be adjusted by controlling Bailey aggregate ratios.