The influence of carbonation on the microstructure of normalised CEM II mortar was studied using nitrogen adsorption and porosity accessible to water. Samples were prepared and subjected to accelerated carbonation at 20°C, 65% relative humidity, and 20% CO2 concentration. Conflicts in results were observed because while the pore size distributions calculated by BJH method from nitrogen adsorption provided evolution of the micro- and mesopores during carbonation, the porosity accessible to water showed changes in all three porous domains: macro-, meso- and micropores. Furthermore, the porous domains explored by water and nitrogen molecules are not the same because of the difference in the molecular sizes. These two techniques are therefore different and help to complementarily evaluate the effects of carbonation. We also examined the evolution of macrophysical properties such as the solid phase volume using helium pycnometry, gas permeability, thermal conductivity, thermal diffusivity, and longitudinal and transverse ultrasonic velocities. This is a multiscale study where results on microstructural changes can help to explain the evolution of macro physical properties.
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