First cycle of desorption and sorption isotherms of carbonated and non-carbonated mortars and concretes using accelerated protocol

Abstract

When a cementitious material is in contact with ambient air, CO₂ enters the material by the porous network and through the cracks, reacts with the CSH hydrates and Ca (OH)₂. These carbonation reactions depend on saturation degree of the material, it does not occur in a fully saturated or totally dry material. Thus, knowledge of isotherms, both for water sorption and desorption, is of interest in modelling the long-term behaviour of these materials. The objective of this paper is to obtain desorption and adsorption isotherms in a short time, and to study the influence of carbonation on the isotherms using an accelerated experimental protocol using thin disc materials of 37.5 mm of diameter and 2 mm thick. The results show that isotherms can be obtained in a significantly reduced time, on the basis of near equilibrium state for each relative humidity levels. The analysis of the distribution of pore radii obtained from the isotherms shows that carbonation causes an increase of the volume of capillary pores while dramatically decreasing the connected porosity of hydrates.

Keywords:

• Cementitious materials
• carbonation
• sorption and desorption isotherms
• pore size distribution