Rheology and Microstructure of Polymer/Asphalt Blends

Abstract

Abstract This work demonstrates the effectiveness of polymers in improving, especially, the high temperature properties of asphalt. The appropriate choice of asphalt, asphalt-grade, polymer type, polymer concentration, and the method of mixing determine if a network-like structure is formed. This morphology significantly improves the creep performance of the binder at elevated temperatures, i.e., the binder has the ability to store deformation energy with subsequent recoil. This is contrary to Newtonian fluids which transform the energy into viscous flow (no recoil). Within the context of dynamic mechanical measurements, the presence of a polymeric network is manifested through the appearance of a plateau modulus. In the case of binders containing block copolymers, we have repeatedly observed that such property improvement in the high-temperature range is generally accompanied by a reduction of the glassy modulus at the low-temperature range as well. It should be noted that by modifying low-viscosity asphalts (i.e., low AC-grades) with polymers, binders can be obtained which exhibit significantly lower moduli at low temperatures and higher moduli at elevated temperatures. This suggests that although using a high AC-grade asphalt may yield satisfactory results at a particular temperature (high temperature), one may instead optimize binders over the entire temperature range (high and low) by starting with a low AC-grade and adding polymer. These results indicate that careful Theological measurements can be a powerful tool in the characterization and design of viscoelastic blends.