Influence of Air Lime type and Curing Conditions on Lime and Lime-Metakaolin Mortars

Abstract

Air-lime mortars with or without pozzolanic components were largely used in the past. Due to natural or accidental degradation the application of repair mortars it is often necessary. Repair mortars have to be compatible with the masonries of historic buildings and should be as durable as possible (without compromising the previous compatibility condition). Within this context and associating the improvement of mortar characteristics with the necessity of sustainable construction practices, mortars formulated with limes and the addition of pozzolans have been studied. Each type of mortar presents its specificities. In pure lime mortars the setting occurs by carbonation and in lime-metakaolin mortars it occurs both by carbonation and hydration. A crucial question in order to optimize the characteristics of the mortars (and its applicability) is related to the curing conditions, which potentiate differently the reaction and consumption of the calcium hydroxide. This article describes an experimental campaign with different pure air lime mortars and lime-metakaolin mortars, cured under different conditions of relative humidity and CO2 content. Properties of the mortars, mainly in terms of mechanical behaviour and open porosity, capillary water absorption, drying capacity and resistance to chloride contamination, are obtained, compared and discussed. The benefits in some properties revealed by the different mortars are correlated with the laboratorial curing conditions and with in situ application possibilities.