The Influence of Natural Organic Materials on the Properties of Traditional Lime-Based Mortars

This article investigates the influence of natural organic materials on the properties of traditional mortars. Mortar specimens produced with two binders (natural hydraulic lime and aged lime putty) with the same sand and three different organic additives (linseed oil, brown sugar, and cow’s milk, with different percentages) were created. The color variations (colorimetry), waterproofing behavior (water capillarity test), permeability (water vapor permeability test), mechanical properties (maximum resistance to compression test), mineralogical composition (X-ray diffraction), and optical properties of mortars (transmitted light microscopy, UV fluorescence microscopy), and carbonation using a phenolphthalein indicator, were evaluated after 28 days, 3, 6, and 12 months. In this article, we highlighted a series of transformations induced by the additives: a strong modification of colorimetric parameters, a general hydrophobic effect of milk and oil not linked to a total occlusion of porosity, a decrease of mechanical parameters in the specimens prepared with hydraulic lime with respect to the specimen without additives, a different distribution and shape of macropores, a different level of carbonation. This article also describes the role of the preparation methods in the influence of natural organic materials on the properties of traditional mortars.