Estimation Model Of Asphalt Content For SAMPAVE Stress Absorbing Layer Mixture

In order to prevent and reduce early reflected crack produced by semi-rigid base or rigid base's temperature shrinkage or dry crack in the overlay of old cement concrete pavement, the new construction, the SAMPAVE Stress Absorbing Layer is developed. This function layer adopts the special modifying asphalt and the specific mineral aggregate gradation, the asphalt content reaches as high as 9%, forms the rich asphalt sand grains type bituminous mixture. The SAMPAVE stress absorbing layer mixture design method is different from other type mixture, and the commonly used Marshall method and the Superpave method for this type mixture design have some shortcomings. Therefore, the research of mixture design method for the SAMPAVE stress absorbing layer should get rid of traditional thought and tries another path. Reasonably determing the asphalt content for the SAMPAVE stress absorbing layer's mixture design has the vital significance for its wide application.This paper has contrasted four theoretical calculation method for specific surface area (including fractal theory method, specific surface area factor method, surface area index method, isolating membrane method), and established the surface area calculation model based on the fractal theory for the SAMPAVE stress absorption layer mixture. Then three measurement methods of specific surface area (BET method, grain size analysis, blaine method) is compared, found that the BET method to test mineral aggregate's specific surface area is more appropriate than others, and the fractal theoretical model predicted value and the actual value are closer. After that, the asphalt film thickness of asphalt mixture influence on the mixture performance is analyzed, considering all of mixture performance index of SAMPAVE stress absorbing layer comprehensively, the reasonable three dimensional film thickness is recommend about 12～13μm. According to determination of mineral mixture's total specific surface area, considering the effective asphalt content and the absorbing the asphalt content by mineral aggregate at the best asphalt film thickness, the asphalt amount estimation velue of SAMPAVE stress absorbing layer mixture is obtained. Through checking calculation on engineering datas of the stress absorbing layer section in Qing-Lan highway and Wu-Huang highway with this model, it is discovered that the prediction model has a good reliability and the applicability.