Effect of Polyphosphoric Acid on Stress Sensitivity of Polymer-Modified and Unmodified Asphalt Binders: Fid-Bau Portal

Effect of Polyphosphoric Acid on Stress Sensitivity of Polymer-Modified and Unmodified Asphalt Binders

Rani, Shivani / Ghabchi, Rouzbeh / Zaman, Musharraf / Ali, Syed Ashik

Polyphosphoric acid (PPA) is known to improve the rutting resistance of asphalt binders by bumping their high-temperature performance grade (PG). However, the stress sensitivity of PPA-modified binders, as an important parameter contributing to rutting, is not thoroughly studied. In the current study, multiple stress creep and recovery (MSCR) test was conducted on three types of neat asphalt binders (PG 58-28, PG 64-22, and PG 70-28), and those modified by 1.0% PPA. Binder blends were subjected to 0.1 kPa and 3.2 kPa stress levels, as well as a higher stress level of 10 kPa, to evaluate their stress sensitivity. The non-recoverable creep compliance and percent recovery values were determined at different test temperatures and the stress levels. The results indicate an increase in the percent recovery and a decrease in the non-recoverable creep compliance due to PPA modification for both non-polymer-modified and polymer-modified binders. However, the increase in the percent recovery is found to be more significant for polymer-modified binder than that for non-polymer-modified binders. It is also found that using PPA reduced the stress sensitivity of polymer-modified binders. Based on the findings of this study, it is anticipated that an increase in traffic level will increase the rutting potential of mixes containing PPA than a polymer-modified asphalt binder of the same high-temperature PG grade. The outcomes of this study are expected to help pavement engineers gain a better understanding of the effect of PPA on the mechanical properties of asphalt binders.