Study On The Volumetric Parameters And Mix Design Method Of SMA

SMA has been used for over ten years in China, but there are still some disadvantages in SMA gradation design and construction technics.The objective of this study was to research the mix design procedure and pavement performance and construction technics of SMA to suit the climate and traffic level and material properties of Simao-Xiaomengyang expressway.The shortcomings of SMA design procedure used in China were firstly presented. Laboratory testing was then performed to evaluate the volumetric parameters and performance properties of SMA mixtures with different aggregate gradations.Analyses of variance (ANOVA) were conducted to evaluate the effect of aggregate gradation and asphalt content on the volumetric properties and performance of SMA. The results showed that the gradation and asphalt content significantly affected VMA and VCA_mix.And it was easier to meet the minimum VMA requirement and the aggregate skeleton requirement for the coraser gradation SMA.But SMA mixture with excessive coarse aggregate would be more probably to have rutting or water damage problems.Based on the theoretical analysis of SMA mixture, a formula indicating the relationship between VMA and VCA_mix and a formula for predicting the optimum asphalt content of SMA were put forward.Further more, a gradation design procedure based on theoretical calculation was presented.Combining with the construction of Simao-Xiaomengyang expressway, the construction technics of SMA are discussed.