An investigation on the deterioration behavior of cement paste in CO2-rich water by an LBM-based reactive transport model

Abstract

The deterioration process of cement-based materials immersed in CO2-rich water is induced by several factors, such as the diffusion of CO2and various ions, the reactions between solutes and the dissolution-precipitation of minerals. In order to understand this phenomenon in an efficient way, a new reactive transport model (RTM) is developed in this work, in which lattice Boltzmann method is selected as a solver for solute transport equations. By utilizing this model, both 2D and 3D simulations are conducted and the results show that a reduction in structural dimensionality leads to an underestimated deterioration rate and inhomogeneous mineral distribution. Besides, calculation frequency is proven to be an important parameter for the RTM, which needs to be carefully calibrated to improve computational accuracy and efficiency. The influence of CO2-rich water’s composition, temperature and curing age on the specimen’s deterioration process are investigated as well. It is found that increased CO2concentration and acidity promote the dissolution of hydration products and the inward movement of calcite precipitation zone, while a reduced temperature hinders the ingress of CO2and this results in a decreased deterioration rate. Meanwhile, a significant drop is observed in the porosity of cement paste at a prolonged curing age, resulting in decelerated rates of both carbonation and calcium leaching.