Comportamento de argamassas de revestimento quanto à retração, fissuração e mecanismo de descolamento em substratos de concreto

Abstract

This research aims to evaluate the retraction, by the mortar superficial movement, occurrence of cracking and detachment of the mortar. Were choosed two types of substrate, one with a 30 Mpa resistance and other with 40 MPa resistance, also were used two types of mortar, one with additive and other lime based, two thicknesses of coating layer, from 15 mm and 30 mm, and was simulated the exposure condition that the region has.For this, tests were performed to characterize the mortar in the fresh state (consistency, water retention, air entrainment and mass density) and in the hardened state (compressive strength, tensile strength in bending, specific gravity, water absorption, voids and density). After preparation of the samples for evaluation, were taken the measures of superficial movement of the mortar for 28 days and the occurrence of cracks and detachment, as well as the verification of the bond strength of the coating and also the loss of water by evaporation of mortars. As a result of this research, it was observed that the variation of the resistance of the substrate analysis not showed a significant difference in the shrinkage, as well as the thickness of the layer to some series. It was also found that the type of mortar, or the material composition, has a direct influence on retraction. With regard to water loss by evaporation from the mortar, it can be seen that the additive achieved greater success in water retention materials. In the test of bond strength, was found that the most significant influence was in relation to the composition of the mortars and that they had values above the minimum allowed by regulatory norm.