Modelling of the evolving contributions of gas transport, cracks and chemical kinetics during atmospheric carbonation of hydrated C3S and C-S-H pastes

A coupled hydro-chemo-mechanical approach to model the degradation and appearance of cracks in cementitious materials subject to carbonation

“…As carbonation proceeds, Portlandite (Figure 4a) and C-S-H (Figure 4b) are progressively dissolved and replaced by calcite (Figure 4c) and amorphous silica (Figure 4d). A more detailed analysis of the amorphous silica precipitation and C-S-H decalcification obtained with our reactive transport model is provided in our previous work 57 . These reactions result in a decrease of the pore-water (Figure 4e) pH and porosity from 0.4 to 0.3 (Figure 4f) in accordance with experimental results 63 .…”

“…Parameters for the reactive transport model (porosity, thermodynamic constants for the liquid-gas-solid equilibrium, water retention parameters, diffusion coefficients and permeability) are described in 57 . The poroelastic parameters of the cement paste (Biot coefficient and bulk modulus k cp ), and the localisation coefficient A CSH of the C-S-H phase, are estimated using the Mori-Tanaka scheme 5,110 and the material properties described in 81 .…”

“…The simulation of the cylindrical sample by a chemical unilateral loading is modeled through a 2D axisymmetric simulation with a 30 mm diameter and a length of 110 mm (Figure 3). For the RT simulation, atmospheric cells are used to model gaseous exchange (CO 2 and water vapor) 57 , while the other boundaries do not allow any mass transfer. No external mechanical loading is applied on the sample, but internal stresses are induced by carbonation shrinkage and the variation of pore-pressure associated to the release of water and porosity changes.…”

“…In practice, carbonation is one of the most detrimental degradation phenomenon for concrete durability as it induces uniform corrosion of the reinforcing steel bars [53][54][55] . This degradation involves the coupling of several processes: gaseous migration and dissolution; mineral dissolution and precipitation as well as porosity evolution 56 ; release, evaporation and transport of water 57 ; solid phase shrinkage [58][59][60] and tensile stresses leading to the appearance of cracks [61][62][63] . 57 have shown that reactive transport modelling alone was not able to reproduce the observed degradation depths and the reaction fronts as soon as a crack pattern was observable.…”

“…This degradation involves the coupling of several processes: gaseous migration and dissolution; mineral dissolution and precipitation as well as porosity evolution 56 ; release, evaporation and transport of water 57 ; solid phase shrinkage [58][59][60] and tensile stresses leading to the appearance of cracks [61][62][63] . 57 have shown that reactive transport modelling alone was not able to reproduce the observed degradation depths and the reaction fronts as soon as a crack pattern was observable. The development of microcracks is attributed to shrinkage induced by both carbonation reactions and drying processes.…”