Comparison of Single Stage and Multistage Permanent Deformation Test for Recycled Asphalt Pavement as a Flexible Pavement Base Layer Material

Abstract

Abstract Recycled asphalt pavement (RAP) has been shown to be a viable material as an aggregate replacement for flexible pavement base layers. Resilient modulus testing shows the potential of the material to perform comparably to virgin aggregate with moisture content, stress history, fines content, and RAP content shown to be influential testing factors. The resilient modulus test provides a quantifiable comparison between materials based on measureable stiffness, but further research must expand testing to determine deformation characteristics for traffic loadings using permanent deformation testing. This paper presented an analytical summary of testing results of multistage and single stage permanent deformation testing of RAP blended with a typical granular fill material. Multistage repeated triaxial loading was used to assess the development of strain in RAP blends under increasing stress loads. This testing method allowed for the study of strain response and permanent deformation with varied stress applications by simpler and shorter methods than single stage testing and the resilient modulus test. The basis of comparison between material samples and test methods of RAP blends was by (1) the strain, stress, and number of cycles where multistage strain is equivalent to single stage strain, (2) the early deformation during each 5,000-cycle loading stage, and (3) the state of stress and the point of failure. RAP blends were less susceptible to strain, and failed after longer testing and higher stresses than class 5 material. The multistage test method provided a single test to display the short- and long-term strain response at varying stress levels to provide further classification methods for RAP.