Nonlinear rheological behaviors of epoxy asphalt binder compared to base asphalt binder and SBS modified asphalt binder at above ambient temperatures

Abstract When heavy vehicles load at high temperatures, the mechanical responses of asphalt binders are probable in the nonlinear viscoelastic regions. However, the nonlinear viscoelasticity of asphalts at above ambient temperatures is seldom studied. In this paper, large amplitude oscillatory shear was used to characterize the nonlinear rheological behaviors of three typical asphalt binders including base asphalt (BA), thermoplastic styrene–butadiene–styrene modified asphalt (SBA) and thermosetting epoxy asphalt (EA) at temperatures of 25, 45, 65, 85, 100 °C, respectively. The inter-cycle yielding behaviors of BA, SBA and EA were observed by strain sweep tests at relatively low temperatures. And the strong intra-cycle yielding and intra-cycle stiffening behaviors were detected for EA at 25 °C, while slight intra-cycle yielding behaviors were observed for BA and SBA through the shape of Lissajous curves. With temperature increasing, nonlinear responses of the three asphalt binders gradually disappear at different rates, which were validated by strain stiffening index S. To some extent, the strain and temperature dependence of nonlinear behaviors displayed in Lissajous curves can be manifested in strain sweep tests. The dissipation ratio φ indicates that with the increase of temperature BA and SBA gradually transform from viscoelastic solids eventually to Newtonian fluids at 100 °C, while EA nearly behaves purely elastic at 100 °C originated from the crosslinking networks. These results could be responsible for the differences of nonlinear characteristics and practical performances among the three kinds of binders.