Investigation into Gradation Optimization of Hot Mix Asphalt

Abstract

This paper puts forward a new gradation optimization and formulated mixture design method. Aggregate gradation affects nearly all aspects of asphalt design from stability to modulus. Aggregate is expected to provide a strong stone skeleton to resist repeated load applications. Traditionally, asphalt mixtures have been designed by using a trial and error procedure to select the aggregate gradation. This realistic problem perplexes many engineers and technicians. Based on the design parameters of California beating ratio (CBR) and void of concrete aggregate (VCA), the experimental investigation of coarse aggregate is carried out. According to dense filling principle, the method of determining fine aggregate gradation is given in this paper. Test results suggest that the proportion of (16mm~9.5mm) & (9.5mm~4.75mm) between 1/1 and 1/2 should be appropriate to receive dense and stronger framework grade blends. Both the VCA crack density (sub DRC) and CBR should be used to optimize aggregate gradation.