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Zhang, Hanyu (2025) Coupled oxidative ageing and mechanical multiphysics modelling of asphalt pavements. PhD thesis, University of Nottingham.

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Abstract

Predicting the long-term pavement performance is one of the most significant challenges in pavement engineering, as it is closely related to pavement design strategies and maintenance decision-making. Pavement oxidative ageing must be considered in the long-term performance prediction, as it predominantly influences the viscoelastic properties and damaging behaviours of road materials throughout their life cycles. To couple the oxidative ageing into the long-term pavement performance predictions, a Multiphysics finite element (FE) modelling framework is developed in this thesis to fundamentally investigate and model the interplay between pavement ageing and performance prediction.

First, a Multiphysics pavement ageing model was developed and validated using measured pavement temperature profiles and ageing products. This model generates variables (temperature and index of carbonyl functional group) that lead to changes in material properties. Second, a time-temperature-ageing shift model was proposed based on free volume theory and validated using the modulus master curves of laboratory-aged materials and the modulus evolution of field asphalt cores. This model links the ageing model with the subsequent mechanical model by producing an intermediate variable, namely, a time-temperature-ageing shift factor. Third, a viscoelastic-continuum damage model under cyclic loading was developed and validated using the strain responses from cyclic indirect tensile (IDT) fatigue tests. This model serves as the material constitutive model for asphalt concrete. Fourth, a temporal homogenisation-based high cycle fatigue model was developed and validated by comparing the model predictions with the traditional cycle-by-cycle simulation results. This model is employed to accelerate the prediction of the pavement performance under long-term loading cycles. Finally, the models described above were integrated into a pavement structural model to investigate how oxidative ageing affects the long-term pavement performance.

Results indicate that the pavement ageing model can capture the spatial distributions and temporal evolutions of temperature profiles and ageing products, effectively reflecting the influence of bitumen ageing sensitivity and asphalt concrete air void content on pavement ageing gradients and evolutions. The time-temperature-ageing shift model simultaneously accounts for the effects of temperature and ageing on the viscoelastic property changes of bituminous materials, serving as a coupling tool between the pavement ageing and mechanical models within the FE modelling of the pavement responses and performance. The developed viscoelastic-continuum damage model for asphalt concrete under cyclic loading can predict the responses and performance at both non-destructive and destructive loadings, successfully identifying the critical numbers of load cycles for the onset of final stage damage evolution. The high cycle fatigue model provides accurate predictions of pavement response and damage conditions with an acceptable computational time (25 min), compared with traditional cycle-by-cycle simulations (209 min).

Pavement oxidative ageing increases the modulus of asphalt concrete and reduces the strain response at the bottom of asphalt layer, which has been validated by the falling weight deflectometer (FWD) measurements at different pavement service years. A modulus gradient along the pavement depth is introduced by the pavement oxidative ageing, leading to the localisation of high stress regions at the road surface. After 16 years of field ageing, more than 50% additional damage would occur at the road surface comparing to the unaged scenario, and the extra damage mainly localises at the edge of the loading area. The pavement remaining fatigue life is reduced by up to 1.6 years due to oxidative ageing in the case study of this thesis, and the top-down cracking is more likely to develop because of the pavement ageing gradient.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Airey, Gordon Thom, Nick
Keywords:	Asphalt Pavement, Oxidative Ageing, Finite Element Modelling, Multiphysics Modelling, Viscoelastic-Continuum Damage Model, High Cycle Fatigue Modelling
Subjects:	T Technology > TE Highway engineering. Roads and pavements
Faculties/Schools:	UK Campuses > Faculty of Engineering > Department of Civil Engineering
Item ID:	81317
Depositing User:	Zhang, Hanyu
Date Deposited:	29 Jul 2025 04:40
Last Modified:	29 Jul 2025 04:40
URI:	https://eprints.nottingham.ac.uk/id/eprint/81317

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