Abstract
The objective of this work was to examine the changes in the microstructure and macro physical properties caused by the carbonation of normalised CEM II mortar. Samples were prepared and subjected to accelerated carbonation at 20°C, 65% relative humidity and 20% CO2 concentration. On the microstructure scale, the evolutions of the cumulative pore volume, pore size distribution, and specific surface area during carbonation were calculated from the adsorption desorption isotherms of nitrogen. We also examined the evolution of macro physical properties such as the solid phase volume using helium pycnometry, porosity accessible to water, gas permeability, and thermal conductivity. The conflict between nitrogen porosity and water porosity results indicated that the porous domains explored using these two techniques are different and help to complementarily evaluate the effects of carbonation. This is a multi-scale study where results on microstructural changes can help to explain the evolution of macro physical properties.
Highlights
Under the action of carbon dioxide from the air and with the presence of water in the pores, several constituents of the cement material are carbonated and form calcium carbonate
The carbonation of calcium silicate hydrate C-S-H: CaSbHc + aH2= CO3 aCaCO3 + bSiO2 ⋅ dH2O + (a − d + c) H2O. The progress of these carbonation reactions causes a change in the microstructure, which is highlighted by various parameters such as variations in porosity, specific surface area and pore size distribution
We propose to investigate the evolution of the microstructure caused by the carbonation in a cementitious matrix using nitrogen adsorption, which is suitable for meso pores with radii of 2 nm to 32 nm
Summary
Under the action of carbon dioxide from the air and with the presence of water in the pores, several constituents of the cement material are carbonated and form calcium carbonate. How to cite this paper: Pham, S.T. The carbonation of calcium silicate hydrate C-S-H: CaSbHc + aH2= CO3 aCaCO3 + bSiO2 ⋅ dH2O + (a − d + c) H2O (2). The progress of these carbonation reactions causes a change in the microstructure, which is highlighted by various parameters such as variations in porosity, specific surface area and pore size distribution. These microstructural evolutions during carbonation lead obviously to changes in macro physical properties such as the solid phase volume, the gas permeability, and the thermal conductivity
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