Evaluation of Cracking Resistance of Tire Rubber–Modified Asphalt Mixtures

Abstract

Cracking is an expensive asphalt concrete (AC) pavement distress to repair. Fatigue and reflective cracking are the two primary types of cracking that impact AC pavement service life. Fatigue cracks initiate at the bottom of an AC layer due to repetitive bending under traffic loads, whereas cracks in the existing AC pavement tend to reflect through the AC overlay quickly. The objective of this study was to evaluate the impact of rubber-modified binders on the fatigue and reflective cracking resistances of AC mixtures. This research evaluated the resistance of unmodified, polymer and tire rubber–modified, and tire rubber–modified AC mixtures to fatigue and reflective cracking. The AC mixtures were designed following the Superpave volumetric mix design method, and dynamic modulus master curves were developed for each mixture. The performance characteristics of the mixtures were evaluated in terms of their resistance to moisture damage, rutting, fatigue cracking, and reflective cracking. Mechanistic analysis of a typical AC pavement was then conducted to assess the impact of the three mixtures on pavement performance life. The mechanistic analysis indicated that the combination of tire rubber and polymer modification offers slightly better resistance to fatigue cracking than tire rubber alone. Both tire rubber mixtures showed superior fatigue performance compared to the unmodified mixture. In the case of reflective cracking, the tire rubber–modified mixtures showed superior resistance to reflective cracking compared to the unmodified and polymer and tire rubber–modified mixtures while maintaining similar resistance to moisture damage and adequate resistance to rutting.