Concrete structures are affected by various environmental factors, such as changes in temperature and humidity, external loads, etc., which cause micro-cracks or damage of different shapes and sizes. This greatly reduces the durability of concretes1. The autogenous self-healing mechanism is one of the methods to effectively extend the lifespan of concretes. This work aims to investigate the autogenous self-healing process of small cracks with a width of less than 0.2 mm in concrete using the numerical method. Autogenous self-healing is consist of the calcium hydroxide dissolution and the precipitation reaction of calcium carbonate. A phase-field model is developed by incorporating the chemical reaction kinetics, diffusion and thermodynamics, and numerically implemented by the finite element method (FEM) within the MOOSE framework. In order to investigate the evolution of the chemistry of the system, a 1D reaction-diffusion model is employed by means of geochemistry PHREEQC calculation code. In this model, the carbon dioxide is added to water at a logarithmic partial pressure of -3.4 in order to model a situation with unlimited supply of calcium hydroxide to the water phase. The simulation results in PHREEQC was used to feed parameters of the phase-field model. We further investigate the microscopic crack morphology by performing multiple simulations with the parameter informed from the experimental tests.

The intention of this project is to work on multiscale modelling to obtain the mechanical properties computation between nano and micro levels of Geopolymer microstructure. Therefore, in this way, we do the simulation of the coarse grained of geopolymer/CNTs from available LAMMPS (Large- Scale Atomic/Molecular Massively Parallel Simulator) trajectory file, which has been computed by molecular dynamics simulation approach. Then, mechanical properties computation through Monte Carlo approaches is defined as the next step, which can be performed by LAMMPS package.

Modelling of a mineral dissolution front propagation is of interest in a wide range of scientific and engineering fields. The dissolution of minerals often involves complex physico-chemical processes at the solid–liquid interface (at nano-scale), which at the micro-to-meso-scale can be simplified to the problem of continuously moving boundaries. In this work, we studied the dif-fusion-controlled congruent dissolution of minerals from a meso-scale phase transition perspec-tive. The dynamic evolution of the solid–liquid interface, during the dissolution process, is nu-merically simulated by employing the Finite Element Method (FEM) and using the phase–field (PF) approach, the latter implemented in the open-source Multiphysics Object Oriented Simula-tion Environment (MOOSE). The parameterization of the PF numerical approach is discussed in detail and validated against the experimental results for a congruent dissolution case of NaCl (taken from literature) as well as on analytical models for simple geometries. In addition, the effect of the shape of a dissolving mineral particle was analysed, thus demonstrating that the PF approach is suitable for simulating the mesoscopic morphological evolution of arbitrary geom-etries. Finally, the comparison of the PF method with experimental results demonstrated the importance of the dissolution rate mechanisms, which can be controlled by the interface reaction rate or by the diffusive transport mechanism.