Influence of natural hydraulic lime content on the properties of aerial lime-based mortars

Blended mortars are commonly used in conservation practices with the purpose of reducing the disadvantages presented by both lime-based and cement-based mortars. However, there is a lack of knowledge concerning the behaviour of such mortars. This paper evaluates the influence of hydraulic lime content on the properties of blended lime-hydraulic lime mortars. For this purpose, mortars composed of aerial lime and different percentages of natural hydraulic lime were tested. Their properties on the fresh state; mechanical strength at early age (28 days) and pore structure, water absorption, drying behaviour and water vapour permeability at long term (3 years) were studied. Blended mortars with hydraulic lime contents higher than 25% showed higher initial mechanical strength and higher water absorption and desorption rates than the aerial lime mortar, with slight reduction of water vapour permeability. As so, these mortars revealed to be more promising to be used as repair mortars than the hydraulic lime one. (C) 2014 Published by Elsevier Ltd.