Effects of moisture on strength and permanent deformation of foamed asphalt mix incorporating RAP materials

Abstract

Based on literature review on moisture susceptibility of hot-mixed asphalt and foamed asphalt (FA) mixes, a 24-h-soaking preconditioning method was selected to evaluate moisture effects on the strength and permanent deformation of FA mixes incorporating RAP materials in this study. Two grades of bitumen and two types of aged RAP materials were considered. Indirect tensile strength (ITS) test and dynamic creep test of FA mixes incorporating different RAP contents and stabilized by the two bitumens were tested under dry and soaked conditions. As well as ultimate strain, creep strain slope and secant creep stiffness modulus under two conditions were analyzed to evaluate moisture susceptibility of FA mixes in permanent deformation. Retained ITS results were evaluated to investigate moisture effect on property of indirect tensile strength of FA mixes. Bitumen grade and RAP content significantly affect ITS result of FA mixes, ITS will decrease with an increase of RAP content under both dry and soaked conditions. Bitumen grade and ageing of RAP material significantly affect moisture susceptibility of FA mixes in permanent deformation. Lower-grade bitumen and less aged RAP material help FA mixes to improve their moisture susceptibility in permanent deformation.