Effects of mineral fillers on bitumen mastic chemistry and rheology

Age hardening of bitumen is one of the key factors determining the lifetime of an asphalt pavement. This study attempts to investigate the effect of different fillers including hydrated lime on mastic ageing. The Thin Film Oven Test (TFOT) was used for short-term ageing, and the Pressure Ageing Vessel (PAV) was used to simulate long-term ageing. The changes due to the ageing are measured by the changes in complex modulus |G*| of the mastics. Chemical changes in the binder were evaluated by the means of Fourier Transform Infrared Spectroscopy (FTIR). Results indicated that different filler mineralogy and properties can significantly affect the rate of oxidative ageing, and this depends mainly on the filler type and concentration. It also showed that hydrated lime reduces the hardening rate more than limestone and granite filler and this correlated with the chemical changes measured by FTIR in terms of rate of change of the carbonyl oxidative products.