Abstract:Based on the volume relationship of aggregate,asphalt, air voids (Va) and voids in mineral aggregate (VMA)in stone mastic asphalt (SMA),the relationship between VMA and asphalt content is discussed and an optimum asphalt content(OAC)equation is deduced.Besides,the influence of VMA on the gradation of SMA is analyzed.According to the deduced relationship of VMA,OAC and gradation,a modified SMA design procedure is proposed.First,VMA is determined as the technology required,and then both the OAC and a more accurate gradation range based on the determined VMA are obtained.Finally,three trail gradations are selected according to the narrowed gradation range;accordingly,specimens using the OAC are compacted.Of the three gradations,the one of the closest Va to 4% is selected as the optimum gradation.A case study is conducted and results show that the modified design procedure for SMA is quicker,simpler and more reliable than conventional design procedures for SMA.
