Investigation of viscoelastoplastic behavior of asphalt mastic: Effects of shear strain rate and filler volume fraction

•Asphalt mastic shows properties of Bingham fluid at 40 °C.•Maximum stress of mastic can be predicted by filler-asphalt interaction, filler volume fraction, maximum stress of asphalt and strain rate.•Shear stress-strain behavior of mastic can be expressed by the stress-strain curve and the peak stress prediction equation. This paper presents the results of a study that used the constant shear strain test to characterize the strain rate dependence of asphalt mastic’ shear stress. A set of shear strain-stress tests was conducted using the dynamic shear rheometer of the Peak Hold program, which can apply constant shear strain to a specimen at a fixed rate throughout testing. The laboratory specimens consisted of two asphalt binders with four different filler volume fractions, respectively. The stress and corresponding strain were measured under various shear strain rates at 40 °C. The relation between the peak stress and strain rate was analyzed to identify the fluid type of asphalt mastic, and a regression model between the peak stress of asphalt bitumen and mastics was derived to predict the peak stress of mastics from bitumen. Then, by combining the regression model with a simple expression of the stress-strain curve, a prediction model was established to predict the shear strain-stress properties under different strain rates and filler volume fractions. Tests on mastics fabricated from a third asphalt binder and another mineral filler were carried out to obtain the shear stress-strain under different strain rate, and these tested results were compared with the results predicted from the equation to show the validity of the prediction model. Finally, the derivation of the prediction model with respect to the strain at different strain rates was used to characterize the damage of mastics during deformation. The results showed that peak stress increased linearly with strain rate, and asphalt mastic could be assumed to be Bingham fluid at 40 °C. The reliability analysis of the prediction model showed that the average error in peak shear stress between the value calculated and measured was 9.8%. The peak shear stress prediction equation, together with the simple expression of the stress-strain curve, provided a reasonably good prediction of asphalt mastic shear stress-strain behavior. Asphalt mastic at higher strain rates had a greater value of dσ/dε, but its decrease was aggravated by increased strain rate.