Formation of porous calcite mesocrystals from CO2–H2O–Ca(OH)2 slurry in the presence of common domestic drinks

Simple method to synthesize porous calcite mesocrystals by aqueous carbonation of portlandite in presence of common domestic drinks.

The Carbonation of Calcium-Silicate-Hydrate C-S-H in Cement Mortar Studied Using Thermal Analysis and Gas Pycnometer: Determination of the Quantity of Calcium Carbonate Produced and the Increase in Molar Volume

The objective of this work was to examine the microstructural changes caused by the carbonation of normalised cement mortar. Samples were prepared and subjected to accelerated carbonation at 20°C, 65% relative humidity and 20% CO2 concentration. The main contributions of this study were: 1) a new way to determine separately the amount of calcium carbonate CaCO3 produced by the carbonation of portlandite Ca (OH)2 and that associated with the carbonation of calcium-silicate-hydrate C-S-H using only thermal analysis; 2) determination of the increase in the molar volume of the calcium-silicate-hydrate C-S-H due to carbonation using gas pycnometer, which indicated an increase of about 39 cm3 for 1 mole of C3S2H3 carbonated. The results indicated that the amount of CaCO3 produced by the carbonation of C-S-H is higher than that produced by the carbonation of portlandite.

Effects of the Type of Cement and the Concentration of CO2 on the Carbonation Rate of Portland Mortars

The objective of this study was to examine the influences of the type of cement and the CO2 concentration on the carbonation progress of cement materials. Thermogravimetric analysis were used to follow mineralogical changes of standard CEM I and CEM II mortars which were submitted to an accelerated carbonation at 20% and 50% CO2, 20°C and 65% relative humidity. The results indicated that the carbonation of portlandite is complete in the case of CEM II mortar while there is a persistence of residual portlandite in the case of CEM I mortar. In other words, the carbonation rate of CEM I mortar is slower than the one of CEM II mortar, which is not only because of its greater content of portlandite but also because of the coverage of portlandite crystals by newly formed calcite. These results allow us to conclude that the carbonation rate of cement mortars depends especially on the type of cement while the CO2 concentration does not affect it at all.