Modified asphalt-rubber green pavement (MARGPave) mixtures: Product development and performance assessment

Abstract

The major objective of this study was to develop “Modified Asphalt-Rubber Green Pavement (MARGPave)” mixtures with dense- and gap-graded aggregate structures to accomplish performance attributes superior to the conventional asphalt-rubber mixtures. The scope encompassed production of one conventional dense-graded, one dense-graded MARGPave, one gap-graded MARGPave, and one gap-graded asphalt-rubber mixtures using the Superpave mix design, conduct of stiffness modulus tests, moisture sensitivity, and fatigue evaluation at varying temperature-frequency combinations, which generated over 300 data points. The dense-graded MARGPave mix exhibited three times higher fatigue life and increased durability than the conventional dense-graded mix. The gap-graded MARGPave mix had lower modulus at all temperatures by more than 50% than the dense-graded MARGPave mix due to 2% higher asphalt content and rubber inclusions. Likewise, the modulus of gap-graded MARGPave mix was higher than gap-graded asphalt-rubber mix across all temperatures and frequencies, indicative of the elastic nature of the MARGPave mix due to higher rubber content. Higher modulus at higher temperatures and lower modulus at lower temperatures were concurrently displayed by dense-graded MARGPave mix, which indicated that the material would be resistant against rutting and low-temperature thermal cracking, thereby able to outperform conventional materials with insignificant rate of change of viscosity with increasing temperatures, and the presence of rubber particles that would render the mix the necessary additional resilience to endure the mix performance for the entire design life. It is noteworthy that the procedure of blending asphalt binder, aggregates, and the modified asphalt-rubber product that replaces some portions of fine aggregates helped create MARGPave mixtures that was found akin to the semi-dry process technology. It is envisioned that the indigenously developed MARGPave mixtures will be best suited as a roadway construction and maintenance strategy that supports the engineering use of end-of-life tires, encouraging the waste-to-wealth concept.