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Coupled Thermal-Hydraulic-Mechanical-Chemical (THMC) approaches may be important for assessing the long-term durability of cementitious materials. We present a multiphysics approach to overcome past limitations of THMC modelling and validate it based on experimental results of accelerated carbonation tests. Our numerical approach rests on a sequential coupling between Hytec and Cast3m. Hytec computes the evolution of hydraulic and mineralogical fields allowing to compute the micromechanical properties (e.g. Young's modulus). The mineral reactions generate tensile stresses and Cast3M computes the associated strain tensors and the damage evolution represented by the opening or sealing of cracks, impacting subsequent reactive transport processes. Our approach manages to qualitatively represent the crack patterns and non-uniform degradation depths observed on microtomographic images of carbonated cement samples, which can only be explained by the coupled dynamics of chemical and mechanical processes. Our approach can be extended to a wide range of cement-concrete pathologies and contexts. [ABSTRACT FROM AUTHOR]

Durability predictions of concrete structures are derived from experience-based requirements and descriptive exposure classes. To support durability predictions, a numerical model related to the carbonation resistance of concrete was developed. The model couples the rate of carbonation with the drying rate. This paper presents the accelerated carbonation and moisture transport experiments performed to calibrate and verify the numerical model. They were conducted on mortars with a water-cement ratio of either 0.6 or 0.5, incorporating either a novel cement CEM II/C (S-LL) (EnM group) or commercially available CEM II/A-S cement (RefM group). The carbonation rate was determined by visual assessment and thermogravimetric analysis (TGA). Moisture transport experiments, consisting of drying and resaturation, utilized the gravimetric method. Higher carbonation rates expressed in mm/day−0.5 were found in the EnM group than in the RefM group. However, the TGA showed that the initial portlandite (CH) content was lower in the EnM than in the RefM, which could explain the difference in carbonation rates. The resaturation experiments indicate an increase in the suction porosity in the carbonated specimens compared to the non-carbonated specimens. The study concludes that low clinker content causes lower resistance to carbonation, since less CH is available in the surface layers; thus, the carbonation front progresses more rapidly towards the core. [ABSTRACT FROM AUTHOR]

The behavior upon exposure to CO 2 of novel cementitious materials prepared with a low clinker cement CEM II/C-M (S-LL) is investigated in this paper. A simplified carbonation model considering the dissolution of a combined Ca-containing hydrate phase (CH, C-S-H, ettringite, monocarbonate, and Si-hydrogarnet) and the precipitation of calcite according to the evolution of phase assemblages calculated with thermodynamic modeling is applied to simulate accelerated carbonation tests in the laboratory. The dissolution rate of the Ca-containing hydrate phase is assumed to be determined by the water saturation degree, the partial pressure of CO 2 , and the fraction of its remaining volume compared to the initial one, which provides a way to predict the precipitation rate of calcite. Two mass conservation equations are considered in the model: water migration through the connected pores and diffusion of carbon dioxide in gaseous phases. Selected physical variables representative of the reactive transport properties are quantified from experimental measurements, including dynamic vapor sorption tests and drying experiments. The model response is compared to experimental data in terms of portlandite profiles from thermogravimetric analysis, and carbonation depth measurements using a pH indicator after specific times of accelerated carbonation. These experiments were also performed on a reference mortar prepared with the CEM II/A-S cement. All experimental results were simulated with the simplified carbonation model and the results compared to the response of the novel material. • Carbonation response of a novel low clinker CEM II/C-M (S-LL) cement is studied. • A simplified carbonation — drying model is coupled with thermodynamic calculations. • Transport properties are identified via DVS tests and drying experiments. • Model is validated against experimental portlandite profiles and carbonation depth. • Performance of the novel CEM II/C-M (S-LL) is compared to existing CEM II/A-S. [ABSTRACT FROM AUTHOR]