Comparisson between damage development on composite and standardized mortar specimens exposed to soluble salts

Abstract

Salt crystallization of lime-based rendering mortars is one of the most common reasons for their deterioration. Still, testing of the resistance to soluble salt action has not yet been standardized for this type of material. Lime-based renders are usually placed in several layers, each of them having a specific role and composition. Nevertheless, tests used in the literature are commonly performed on standardized prismatic or cylindrical mortar specimens. This paper presents a comparison between damage development on the composite samples, prepared on porous stone substrate with two types of rendering mortars, and standardized prismatic mortar specimens. Samples were prepared with pure putty lime mortars and lime-putty based mortars with the addition of natural zeolite. Two types of composite samples and four types of prismatic samples were used during the test. The testing was conducted at the age of 90 days using two types of salt solutions (NaCl and Na2SO4). Damage development was followed visually during five cycles of wetting and drying. Salt distribution using XRF analysis was measured at the end of the test on composite samples. It was shown that damage development greatly depends both on sample and mortar types.