Water resistance of tile adhesive mortars formulated with various binder technologies

The paper presents the results of water and cyclical freeze – thaw resistance tests of cementitious mortars based on 3 different binders: Portland cement, calcium sulfoaluminate cement and belite-ye’elimite-ferrite cement, modified with organic additives: methylcellulose and redispersible polymer powder based on vinyl acetate-ethylene copolymer. The tests of mechanical strength were conducted in 2 modes: compressive strength of prisms and pull off strength of samples applied as a thin layer on the concrete substrate. The mechanical tests were complemented with phase composition analysis by the means of X-ray diffractometry. The evidently negative effect of organic admixtures on the water resistance of all mortars was found, whereas the scale of strength decrease depends on the cement type used. It was also shown that adverse impact of organic additives on water and frost resistance is more pronounced in case of pull off strength measurements than in case of compressive strength of prisms. The mechanical results could not be explained on the grounds of mineral matrix compositions traced by XRD method. In the further parts of the paper possible alternative explanations of the described observations were discussed.