Laboratory study on permanent deformation of foamed asphalt mix incorporating reclaimed asphalt pavement materials

For the purpose of investigating the effects of bitumen grade, content of reclaimed asphalt pavement (RAP) material and ageing of RAP, this paper presents the evaluation of permanent deformation of foamed asphalt (FA) mixes by using the dynamic creep test. The mix design of WC-20 was conducted based on the gradation requirement of FA mix and RAP aggregate size. Three parameters, creep strain slope (CSS), Intercept and secant creep stiffness modulus (SCSM), were used to analyze the test results. Mean comparison and multiple analysis of variance (MANOVA) reveal that bitumen grade significantly affects CSS, whilst content and ageing of RAP would have insignificant effect on CSS. High bitumen grade may help FA mixes on the reduction of susceptibility to permanent deformation. Test results reflect that variances of CSS, Intercept, and SCSM are large. There is a good exponential relationship between CSS and SCSM, however no correlation between CSS and air void is found. Comparison of test results between FA mixes and hot asphalt mixes exhibits that susceptibility and creep strength of FA mixes are better than those of selected hot asphalt mixes.