Linear and Nonlinear Rheological Properties of Bituminous Mastics under Large Amplitude Oscillatory Shear Testing

Abstract

This paper studies the linear viscoelastic behavior under small strain amplitudes and the nonlinear behavior using large amplitude oscillatory shear (LAOS) tests performed at strains beyond the linear viscoelastic regime of bituminous mastics. Four types of mineral fillers—blast-furnace slag (BFS), silica fume (SF), fly ash (FA), and hydrated lime (HL)—with particle sizes less than 75 μm are used to prepare the asphalt mastics with proportions of .7 and 1.15 based on the mass of base binder. For the linear rheological measurements, small strain oscillatory shear testing is carried out within the linear regime of the materials. The nonlinear viscoelastic properties are investigated using the LAOS test performed at 4°C and 1 Hz to examine Lissajous-Bowditch plots and by analyzing the elastic and viscous nonlinearities of the mastics at strains of .5, 1, 2, 3, and 4%. The linear viscoelastic region (LVER) of the mastic and base binder depends not only on the strain amplitude but on the testing frequency and temperature as well. The filler type and concentration have an obvious influence on the linear viscoelastic properties of their mastics. The HL and SF fillers outperform the linear viscoelastic properties of the BFS and FA in terms of the complex shear modulus. The Lissajous-Bowditch plots become progressively distorted with the increase of strain amplitude and show an increase in the exerted stress with the addition of mineral fillers. The local nonlinear measures of an oscillatory LAOS cycle are able to quantitatively differentiate between the properties of studied mastics at different strain amplitudes. The mastic that shows the best performance in the linear regime is not guaranteed to perform superiorly in the nonlinear regime. The results can be used to differentiate or rank the properties of mastics and/or asphalt binders at different strain amplitudes in a quantitative manner.