Effect of select warm-mix additives on thermo-viscoelastic properties of asphalt mixtures

In this paper, the thermo-viscoelastic properties of hot and warm asphalt mixtures from South Dakota, USA, were determined from direct measurements of thermally induced stress and strain. The approach to determine the relaxation modulus, viscous flow, viscous-glassy transition, glassy hardening, crack initiation, and fracture stages was described and used to assess the influence of select warm-mix additives on low-temperature properties. The evaluated warm-mix additives as well as the aggregate source were found to have inconsistent effects on the thermo-viscoelastic properties of the mixtures. It was observed that mixtures with similar thermal stress build-up can have significantly different relaxation modulus values depending on the coefficient of thermal contraction of the respective mixture. In summary, the proposed methodology was able to discern the slight differences caused by the warm-mix asphalt treatments on the same binder and two aggregates.