A novel meso-scale numerical implementation of the carbonation kinetics of cementitious materials

Carbonation tests of hardened cementitious materials are time-consuming even under accelerated conditions, presenting significant challenges for the design of experiments. It is widely acknowledged that utilizing a low CO https://www.w3.org/1998/Math/MathML" display="inline"> 2 concentration ( https://www.w3.org/1998/Math/MathML" display="inline"> < 3 % ) is critical to accurately replicate natural carbonation conditions. Hence, a model is called for to estimate the carbonation front during accelerated carbonation tests of the designed composition a priori . In this paper, we first introduce a Finite Element Method (FEM) implementation in COMSOL Multiphysics that models a one-dimensional (1-D) reactive-transport process for OPC-based materials. Secondly, an equivalent FEM model is implemented in MARS (Modeling and Analysis of the Response of Structure). After benchmarking this model against the COMSOL model, we establish a novel three-dimensional (3-D) meso-scale model using the dual-lattice Multi- physics Lattice Discrete Particle Model (M-LDPM) framework. A CO https://www.w3.org/1998/Math/MathML" display="inline"> 2 concentration of 1 % is applied in both implementations, with a constant temperature field of 20°C and a relative humidity of 65 % to simulate accelerated carbonation tests in an environmental chamber. It is shown that the meso-scale model can predict the average carbonation depth while retaining the heterogeneity of concrete and, thus, the spatial variability in the carbonation front. Advantages and disadvantages of both implementations are discussed, providing insights into their applicability in simulating real-world carbonation processes that can help researchers in their design of experiments.