Design method for aggregate gradation of porous asphalt mixture based on target air voids

The air voids is a critical indicator in the design of porous asphalt mixture (PA). Currently, aggregate gradation design for PA uses air voids solely as a verification indicator, rather than integrating it directly into the gradation design process, which may lead to PA design tedious and time-consuming. The objective of this study was to present a method for designing the aggregate gradation of PA based on the target air voids. Initially, using the volume composition of compacted asphalt mixtures and the formula for estimating asphalt-aggregate ratio, a physical model was established to link air voids with the content of fine materials (i.e. passing percentage of key sieves). Subsequently, a determination method for the critical parameter of the percentage voids in coarse aggregate (VCA) within the physical model was provided based on the skeleton stability of coarse aggregate using a penetration test. Finally, a procedure for designing the aggregate gradation of PA based on target air voids was proposed employing the established physical model. Additionally, an applied case study on the gradation design of PA-13 was presented, verifying the effectiveness of the method. The design method proposed in the paper can serve as a reference for aggregate gradation design of PAs with various requirements for air voids, significantly reducing the experimental workloads and time.