Peridynamic and discrete multiphysics for modelling the mechanical and fracture properties of pavement materials

Sanfilippo, Danilo ORCID: 0000-0003-3938-5756 (2023). Peridynamic and discrete multiphysics for modelling the mechanical and fracture properties of pavement materials. University of Birmingham. Ph.D.

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Abstract

Asphalt pavement experiences different degradation mechanisms under several solicitations. The asphalt mechanical and fracture properties of asphalt mixtures have been investigated using experiment and X-ray CT scan to improve the quality of design. These methods are limited by the number of samples required and high cost. The development of numerical methods provided a powerful tool to investigate the asphalt mixture performance at macro and micro scale, requiring lower number of sample and cost. A key challenge of the numerical method is the reliable modelling of the cracks under different conditions.

In this thesis, Peridynamics and Discrete Multiphysics model is used to simulate the mechanical properties and fracture characteristics of pavement materials. The simulations were carried out on the open-source software LAMMPS and visualised on Ovito. Initially, the capability of Peridynamics and Discrete Multiphysics was explored to assess micro-crack formation and propagation in asphalt mixture at low temperatures and under freezing conditions. The results showed the cracks form at the interface and propagate from one void to another along the direction of load. In addition, the water expansion increases the pressure within the voids which adversely has a detrimental effect on the asphalt mixture performance. Experimental studies on three different asphalt mixtures with voids content of 3%, 10%, and 14% were performed at low temperature and freeze-thaw cycle to establish a correlation between the asphalt mixtures’ properties and the voids’ topology. The asphalt mixtures were scanned using Computer Tomography scan to determine the internal structure that evolves during freezing cycles. Semi-circular bending test was used to determine mechanical properties at low temperatures. The results show that asphalt mixture with 3% void content has the lowest and steady degradation rate with the lowest water retention during all cycles. The asphalt mixtures with a 3 high void content have the highest concentration of water in the pores and decay faster during the initial cycles, but slower during the later cycles because there is less water inside the pores which are fully open and do not retain it. A 3D model was used to simulate the asphalts mechanical and fracture properties discussed in the previous chapter at -10 °C. In addition to the previous chapter, asphalt mixtures mechanical and fracture properties at 20 °C were simulated. The results showed that the asphalt mixture performance is reproduced with 23.08% error for the asphalt mixture at -10 °C and 6.9% for the asphalt mixture at 20 °C compared to the experiments. The damage at low and high temperatures such as cracking was reproduced like the real sample. In addition, higher stress occurs in the area where damage was formed.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):