Lime-earth mortars: characteristics and applications

Abstract

Earth-lime mortars probably result from professional practices from the time when economical conditions enabled the addition of air lime to vernacular earth mortars, which are not durable when in contact with water. Previous studies have shown that the addition of low contents of air lime on earth mortars with dark colour, while turning the mortars water resistant, makes their colour lighter and weakens their mechanical characteristics. This study examines the partial weight replacement of lime by a local earth in air lime mortars with a 1:2 lime: sand volumetric proportion, corresponding to mortars with a 1:8 weight proportion, with replacements from 10 to 50%. The embodied energy of mortars is reduced by their formulation, and they are adequate for use as render in old buildings and also on new constructions with compatible characteristics. The results of the mechanical and physical characteristics, as well as on the reaction to sulphates attack, were particularly positive for a 10% lime replacement by earth, with variations between the assessed properties. Nevertheless, further research is still needed for a deeper knowledge of the characteristics of lime-earth mortars, widely used in the past, in order to optimise formulations to be applied in the present day.

Keywords:
Air lime; Clayish earth; Masonry; Render; Repointing