Effect of fatty acid soap on microstructure of lime-cement mortar

Different additives based on Na oleate, Na oleate - Ca stearate and Al stearate were used in two different quantities (0.15 %w/w and 0.30 %w/w of the solid amount) to enhance the waterproofing effect of mortars. From capillary water absorption test, Na oleate showed the better performance with a reduction of water absorbed of 86% in comparison with the reference mortar. The microstructure showed the presence of microcavities ranging between 0.01 mm and 0.2 mm, due to air bubbles trapped during the mortar preparation for the surfactant effect of Na oleate. The presence of a higher amount of pores (210 mm3/g vs. 175 mm3/g) was confirmed by the Hg porosimetry. Moreover a reduction of the carbonation rate for the presence of additive was verified.