Rheological analysis of asphalt binders modified with Elvaloy® terpolymer and polyphosphoric acid on the multiple stress creep and recovery test

Abstract

This study presents the results of a series of creep-recovery experiments that were conducted on asphalt binders modified with polyphosphoric acid (AC+PPA) and Elvaloy® terpolymer combined with polyphosphoric acid (AC+Elvaloy+PPA) at the temperatures of 52, 58, 64, 70 and 76 °C. The multiple stress creep and recovery (MSCR) test was used to determine the percent recoveries (R), the non-recoverable compliances (Jnr) and the percent differences in non-recoverable compliances (Jnr, diff) of these modified asphalt binders and the ones of the 50/70-penetration grade base material. The base material is graded as PG 64-xx and the formulations with PPA and Elvaloy+PPA are graded as PG 76-xx. Two pairs of loading–unloading times were used in the MSCR tests, namely, 1/9 s and 2/18 s. The AC+Elvaloy+PPA shows not only the highest R values and the lowest Jnr values, but also the lowest sensitivity to a sudden increase in the stress level inside the asphalt mixture. Although the results are not as promising as the ones found in the AC+Elvaloy+PPA, the AC+PPA may be taken as an alternative to replace the unmodified asphalt binder when the loading and/or the climate conditions are more severe.