Changes in Water Adsorption Desorption Isotherms of Cement Mortars Caused by Carbonation Coupled with Humidification-Drying Cycles

Abstract

The objective of this work was to examine the influence of carbonation on the water vapor adsorption desorption isotherms of cement materials. Two types of Portland mortars, which were CEM I and CEM II, were carbonated at 20°C, 65% relative humidity and 20% of CO2concentration. The pore size distributions were determined from the water adsorption method. We also studied the coupling effect between carbonation and humidification-drying cycles. The results showed a reduction in microporosity and a small increase in the mesoporosity. The pores clogging due to formation of calcium carbonate was highlighted by the reduction of the quantity of adsorbed water and the decrease in the hysteresis isotherms. The results of this study also indicated that the humidification-drying cycles coincide only from the second cycle because of a difficult evacuation of water during desorption, even at low humidity.