CRACKING RESISTANCE OF LIME COATINGS WITH POLYSACCHARIDE

Lime compositions are widely used for finishing and restoration of buildings and structures of historical development. To increase the durability of lime coatings, various modifying additives are introduced into the formulation. Excavations of ancient structures indicate the presence of organic additives (sticky rice, egg white, plant extracts or animal blood) in lime solutions. The purpose of this work is to study the effect of synthetic polysaccharides on the resistance of lime coatings to cracking. To assess the cracking of lime coatings, a technique was used based on the relationship between the crack length, the Vickers indenter imprint and the fracture toughness. It was found that the introduction of synthetic polysaccharides into the formulation of lime compositions helps to accelerate the gain in plastic strength of the compositions and increase the frost resistance of the finishing layer. Due to the water-retaining effect of the additive, more favorable conditions are created for lime carbonation. It was found that coatings based on the composition with the addition of the synthetic polysaccharide Atren Cem LV are characterized by a higher value of the critical stress intensity factor, amounting to K1c = 0.074 MPa m, which indicates their higher crack resistance. The average length of cracks formed in the coating with the addition of polysaccharides Atren Cem LV is less compared to the control compositions. This indicates a higher crack resistance of lime coatings with polysaccharide additives.