Mechanical Evolution of Lime Mortars during the Carbonation Process

Lime mortar is one of the most ancient and durable building materials. It is characterized by a slow carbonation during which Ca(OH)(2) reacts with CO2 present in air and forms calcite, giving rise to a stronger and more compact material. This process takes place from the surface to the interior of the material and it is strongly affected by the reaction conditions. The aim of this study is to quantify the increase in strength and elasticity of different lime mortars according to their carbonation degree. For that, six types of mortars were elaborated, with different lime/aggregate proportions and aggregate mineralogy and grading. Mineralogical and textural studies were carried out to follow the carbonation process. Each mortar was tested in a uniaxial compression press after 15, 28, 60 days from the elaboration. In order to differentiate the mechanical behaviour of the external and internal parts of the mortars, two micro-samples (10x10x10 mm) were obtained from the first 10 mm and from the core of each prism. Results show that an increase in strength and especially in the elastic modulus is associated to the carbonation process, but it is different depending on the composition and compactness of the mortars.