Experimental study on the humidity in aerial lime mortar

Abstract

A significant part of the historical heritage around the world consists of masonry structures, with joints filled with mortar. In these structural systems, mortar usually represents a small/moderate portion of the total volume of the structure. However, the mortar is recognized as the main source of deformations/displacement in the structure, this fact justifies the necessity of an appropriated knowledge of its behavior. In ancient mortars, aerial lime is one of the earliest and recurring binders around the world. In these mortars, the hardening of the material is gradual from the surface, in correspondence with the carbonation and drying processes. For these mortars, these two cited processes affect various properties of the material. For aerial lime mortars, the study of carbonation is widespread in the literature, diverse authors already study the topic. However, for the moisture diffusion processes, the number of studies is still quite reduced. During the mortar preparation, some of the water applied during the mixing is evaporated by the exothermic reaction of hydration. However, an elevated moisture content remains. In this work, studies are carried out to investigate the internal humidity fluxes in aerial lime mortars. The experimental program begins with the characterization of the materials, as well as the definition of the mortar composition. Experimental work was carried out on specimens stored in a controlled environment, with geometries simulating uniaxial and axisymmetric flows. The monitoring of internal moisture of specimens at various depths was carried out. The results indicated an accelerated diffusion, with a rapid decrease of humidity when compared with usual values observed in cement-based materials.