Measurement of CO2 effective diffusion coefficient of cementitious materials

The CO2-effective diffusion coefficient is a key parameter in the modelling of carbonation of cementitious materials. It is usually deduced from empirical relationships determined by tests on mixtures made with OrdinaryPortland Cement (OPC). These relationships are a priori non-valid for materials with high content of mineral additions, such as ground granulated blast furnace slag (BFS). In order to better understand the effect of composition on the CO2 effective diffusion coefficient, a device was developed to measure this property. This study presents the developed protocol and the study carried out on dried cement pastes and limestone samples. The influence of several parameters was investigated: material nature, water/binder ratio, binder type (OPC or BFS). BFS pastes were found less diffusive than OPC pastes for the same porosity. CO2 diffusion is strongly affected by the pore structure properties. Comparison with literature results is mixed. Effective diffusion coefficients determined in the present study are only of the same order of magnitude than coefficients measured through CO2 diffusion tests.