Using steady shear rate sweep protocol to determine zero shear viscosity of unaged and aged unmodified bituminous binders

Abstract

Rutting is one of the most significant distresses occurring in bituminous pavements at higher pavement temperatures. Researchers have been focusing on developing bitumen binder parameters that can be used to predict the rutting resistance of bituminous mixtures, and zero shear viscosity (ZSV) has proven its efficacy as a binder rutting parameter. A stepwise steady shear rate sweep test with two cycles of forward and backward sweeps was conducted at very low shear rates to determine the ZSV of unaged, short-term aged, and long-term aged unmodified bitumen binders. Convergence of the steady-state viscosities was observed at different shear rates in the first forward sweep. The response of the binders was independent of the shear rate, time, and the effect of shear history was negligible. As the shear rates corresponded to the ZSV regime, the ZSV was determined from the first forward sweep. The ZSV correlated well with the three existing rutting parameters.