A study on rutting susceptibility of asphalt binders at high stresses using MSCR test

Abstract

Recently multiple stress creep recovery (MSCR) test is recommended to evaluate rutting performance of asphalt binders. The non-recoverable creep compliance (Jnr) parameter, an indicator of rut resistance of an asphalt binder is estimated at 3.2 kPa stress from the MSCR test. Further, Jnr is used to rank asphalt binders for different loading conditions. However, many studies reported that maximum stress of 3.2 kPa in the current MSCR protocol may not capture high stress scenario resulting from heavy loading. Thus, evaluating performance under high stresses may help to better characterize asphalt binders for excessive loading conditions. Therefore, the present study was undertaken to evaluate rutting potential of three different asphalt binders: unmodified (VG 30), SBS polymer modified asphalt binder (PMB 40), and crumb rubber (ground tire rubber) modified (CRMB60) at different levels of stress: 3.2, 6.4, 12.8 and 25.6 kPa, tested at 52, 64 and 76 °C.The paper presents effects of high stresses on Jnr, percent recovery (R), percentage difference between Jnr at two stress levels (Jnr,diff), and ranking of asphalt binder. It was found that combined effects of stress and temperature can have significant impact on performance of asphalt binders. The results show that an increase in stress results in high Jnr, decreased R, and increased Jnr,diff for all the asphalt binders. The plot between Jnr and R gives a better picture of performance of asphalt binders. The R and Jnr values should be coupled together to evaluate potential of asphalt binder suitable for different traffic loading and temperature conditions.