Parameter optimisation of a 2D finite element model to investigate the microstructural fracture behaviour of asphalt mixtures

To mitigate the risk of asphalt degradation of pavement surfaces and to increase the durability, there is a need to investigate the fracture behaviour of asphalt mixtures at low and intermediate temperatures. The indirect tensile test (IDT) is widely used to characterise the fracture resistance in terms of tensile strengths of the asphalt mixtures. This paper presents an optimised method for two-dimensional (2D) finite element (FE) modelling of the IDT to simulate crack initiation and propagation within the asphalt mixtures on the microscale. X-ray computed tomography (X-ray CT) scanning and digital image processing (DIP) techniques were applied to detect and reconstruct the microstructure of asphalt specimens. Cohesive zone modeling (CZM) techniques were applied in the FE simulations to represent the fracture behaviour. The procedure of the FE modelling and parameter optimisation are described comprehensively. Four important parameters governing the numerical solutions during the simulation process were optimised based on counts of accuracy as well as computational efficiency. The optimised models were also validated based on experimental results. As a case study, the influence of the loading orientation on the fracture behaviour of asphalt mixtures was investigated. The validation and case study prove the reliability and applicability of the proposed FE modelling algorithm; further improvements will be carried out to facilitate the development of the pavement design process.