Permanent Deformation Behavior of Foamed Bitumen Stabilized Mixes

Abstract

This paper investigated the deformation (dynamic creep) behavior of foamed bitumen stabilized mixes (BSM-foam) that incorporates recycled asphalt pavement (RAP) material. The influence of temperature and stress level on the deformation behavior of these mixes was studied. The permanent deformation indicators that were determined using the laboratory tests on BSM were also compared with those of the conventional hot mix asphalt (HMA). From the comparative studies using dynamic creep tests, it was noted that the three-stages (primary, secondary and tertiary) of the creep curve that are usually seen for HMA were also observed for BSMs. The mathematical models that are commonly used to fit the different stages of the creep curve of HMA were found to be applicable to predict the creep behavior of the BSMs. In general, it was found that the BSMs behave similarly to that of HMA in terms of permanent deformation in that a steady-state strain rate was achieved before failure. From the repeated load axial test (RLAT) tests, it was noticed that the BSMs are less temperature-sensitive to deformation compared to HMAs. BSMs showed 20%–45% less of an increase in permanent deformation compared to HMA when test temperature increased from 30°C to 50°C. This study also investigated the applicability of the time-temperature superposition (TTS) principle for secondary stage permanent strain data obtained from RLAT tests. The RLAT tests were conducted at three temperatures and three stress levels to develop the dynamic creep master curve. It was observed that the TTS principle is applicable for secondary creep data of BSMs.