Comparative evaluation of laboratory and field ageing of asphalt binder using a non-linear differential model

Abstract

Aging of asphalt binders leads to evolution of pavements’ mechanical performances. To study the ageing process and ageing behaviour of asphalt binder, a rolling thin film oven test (RTFOT) and a self-designed ventilation oven test at 60°C (VOT) were conducted on five regular asphalt samples in the laboratory, and aged asphalt was extracted from six pavement sections of different service lives. Viscosity of asphalt samples was fitted with a non-linear differential dynamic model by numerical analysis software, and two parameters of L and r for different ageing approaches are obtained. With the two parameters, the ageing process of these asphalts under different ageing conditions was discussed, and the relationship between simulation ageing and field ageing was investigated. The results indicate that the non-linear differential dynamic model can effectively evaluate the asphalt ageing process in the laboratory and in the field. The model parameters (L and r) can be used to quantify the ageing state and ageing rate. Asphalt has its ultimate ageing state corresponding with different ageing temperatures. The ultimate ageing degree of RTFOT and field ageing is about 4–5 times that of VOT. The ageing effect shift factor is approximately 60 min of extended RTFOT ageing to represent 1 year of field ageing. Thus time-extending RTFOT can simulate the long-term ageing of pavement asphalt. And the parameter L or r may be used to predict the extent of ageing in lab-aged materials.