Modelling and validating the time-temperature-ageing superposition principle in bitumen via molecular dynamics simulations

The durability and performance of asphalt pavements are dominantly determined by the viscoelastic properties of bitumen. Time-temperature-ageing superposition principle (TTASP) theory can effectively reflect the effects of ageing and temperature on the viscoelastic properties of bitumen. However, obtaining the parameters of TTASP experimentally is time-consuming and challenging. Accurate and rapid acquisition of the parameters of TTASP is needed. In this paper, molecular dynamics (MD) simulations are used to explore the volumetric properties of bitumen, verifying the TTASP and obtaining its parameters from a molecular computational perspective. The bitumen molecules were developed in the MD according to the proportion of the lab-measured bitumen. The TTASP parameters were derived and calibrated via fractional free volume theory, considering the model size effect influenced by the number of molecules. The degree of bitumen oxidised ageing was investigated in the MD via the carbonyl groups. The proposed method effectively verifies the rationality of Time-temperature superposition principle (TTSP) and TTASP theories at nanoscale, accurately predicting volumetric and TTASP parameters. This precise and efficient approach can be used to forecasts the viscoelastic properties and ageing behaviour of bitumen, ensuring reliable predictions consistent with experimental results.