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

Air-lime mortars with or without pozzolanic components were largely used in the past. Due to natural or accidental degradation it is often necessary the application of repair mortars, durable and compatible with the masonries of historic buildings. Within this context and associating the improvement of mortars characteristics to 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 with 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 chlorides 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.