Pore structure and carbonation in blended lime-cement pastes

Abstract

The present study aims to gain a fuller understanding of the curing process in lime pastes (100, 90, 80, 70, 60, 50 and 40% lime) blended with cement by analyzing carbonation in these materials. A hydrated, air slaked lime powder and CEM II A/L 32.5 Portland cement were used for the blends. These materials were singled out for research primarily because they may be used in the restoration of heritage monuments. Variation in weight was used as an indicator for carbonation. A new parameter, A, was found to vary inversely with the percentage of the cement because of the prevalence of Knudsen diffusion in the paste, in turn due to the characteristics of the pore structure, which was studied by mercury intrusion porosimetry (MIP). The hygroscopic study conducted on the different pastes provided information on water content at a given humidity and its location, i.e., adsorbed on the surface of the pores or condensed inside them, obstructing the diffusion of CO2 . The conclusion drawn from this study of the curing process was that neither drying nor C3 S hydration retarded lime carbonation.