Ageing effects on the linear and nonlinear viscoelasticity of bituminous binders

The paper investigates the effects of ageing on the linear and nonlinear viscoelastic properties of bituminous binders for paving applications. Four neat binders were analysed in their unaged state and after long-term ageing, which was simulated in the laboratory with the Rolling Thin Film Oven (RTFO) and the Pressure Ageing Vessel (PAV). Amplitude sweep tests and frequency sweep tests were performed to explore the response in the linear domain. Repeated strain sweep tests were carried out to isolate nonlinearity from other mechanisms related to damage. The time–temperature superposition principle and the generalised Maxwell model with a Prony series discretization were used to describe the overall viscoelastic response of binders, introducing strain-dependent shift factors to account for nonlinearity. Results indicate that the adopted experimental and modelling approach allows a proper assessment of the effects of ageing on viscoelasticity.