Optimal design and validation of double-layer porous asphalt structure based on thin-layer process

Abstract

Double-layer porous asphalt (DLPA) pavement has been gradually applied in China for its efficient water drainage and noise reduction. However, it also faced the challenge of relatively low overall performance for the large air voids. This paper proposed a method of optimizing DLPA structure into a thinner three-layer porous asphalt (TLPA) structure for achieving lower air voids. Specifically, the optimal thickness of porous asphalt (PA) was determined by analyzing the relationship between PA mixture thickness and the degree of segregation. Then the application rate of tack coat between the middle and bottom layers of the TLPA structure was determined. Thirdly, based on the principle of equal drainage speed in TLPA structure, air voids of each PA layer were confirmed by a prediction model, which considered the relationship of air voids, thickness, nominal maximum aggregate size (NMAS), and drainage capacity. Finally, the feasibility of this thin-layer method was validated. Results indicated that PA mixture thickness exhibited good uniformity at 2.5 times of NMAS. It should have considered the effects of air voids, thickness, and NMAS on PA mixture permeability during functional design processes. Converting a DLPA structure to a TLPA structure was feasible, and it could greatly have reduced air voids of the top layer.