Three-Stage Evolution of Air Voids and Deformation of Porous-Asphalt Mixtures in High-Temperature Permanent Deformation

Abstract

The objective of this paper was to investigate the evolution of air voids (AV) and deformation and the failure mechanism of porous asphalt (PA) mixtures under high temperatures. An advanced repeated loading permanent deformation (ARLPD) test was used to investigate the high-temperature permanent deformation of PA mixtures. A staged ARLPD test (first stage test, secondary stage test, and third stage test) and a staged X-ray computed tomography (CT) scanning test were designed to evaluate the three-stage evolution of the AV and deformation in the ARLPD test. Total AV content (AVtotal) and interconnected AV content (AVinterconnected) decrease in the first stage, and AVtotal, AVinterconnected, and the number of AV (AVnum) increase in the secondary stage. AVtotal and AVinterconnected decrease and AVnum increases in the tertiary stage. Based on the changes of AV and intuitive image analysis, the failure mechanism of PA mixtures was discussed. The first stage is a densification stage, during which radial deformation develops faster than vertical deformation. Densification failure was observed in the tertiary stage, which shows that vertical deformation develops faster than radial deformation.