Optimization design and verification of Large Stone Porous asphalt Mixes gradation using Compressible Packing Model

Abstract

As a unique gradation type of asphalt mixtures, Large Stone Porous asphalt Mixes (LSPM) has advantages in promoting pavement performance including cracking resistance, rutting resistance, and moisture susceptibility. The gradation design is a critical determining factor for the LSPM performance. Therefore, this paper aims at optimizing the gradation design of LSPM, as well as testing its mechanical performance and microstructural characteristics. Firstly, a new gradation of LSPM is designed and optimized on basis of the Compressible Packing Model (CPM) theory. Then, the basic pavement performance of the new LSPM are verified, and compared to an existing LSPM. The cracking resistance of the new and existing LSPM is measured by the Overlay Tester. Meanwhile, the pore structure characteristics are analyzed for further elaborating the differences between the two mixes. The result shows that the CPM model can simulate packing state. The new LSPM gradation is proposed using the CPM and correction coefficient k. The first cycle load loss rate P1 and loading cycles of 50% load loss rate N0.5 can evaluate the anti-reflection cracking performance more effectively. Air void content of LSPM in vertical direction is heterogeneity distribution. The macropores and extra-macropores are major components of pores, above 80% of all. It indicates that the CPM method is applicable in LSPM gradation design. Moreover, performance of the optimized LSPM have been significantly improved.