An investigation of asphalt durability: Relationships between ductility and rheological properties for unmodified asphalts

Abstract

Literature reports indicate that the ductility of binders recovered from asphalt pavements correlate with cracking failure. However, ductility measurement is a time and material consuming process, and subject to reproducibility difficulties, as are all failure tests. The purpose of this study was to correlate ductility with DSR properties analogous to the SHRP procedure of using BBR S and m to screen for the thermal cracking. DSR measurements are much faster and consume much less material than ductility measurement. Fourteen unmodified asphalts were oxidized to different levels of aging at temperatures ranging from 60 to 200°C. Experimental data show that the extensional flow of conventional asphalt binders can be qualitatively described with a simple elongation model using a viscoelastic Maxwell element. Based on this model, a map of the dynamic shear modulus G′ vs. η′/G′ was used to track changes in ductility with aging. Also, ductility correlated remarkably well with G′/(η′/G′) for different binders aged at different conditions.