Cementitious adhesives performance during service life

Abstract

Ceramic tiles have been extensively used on external walls in Portugal for many years. These tiles are often bedded into mortar or into a cement-based adhesive. In the last few years, however, there have been many mistakes, such as adhesion failure, in the use of ceramic wall tiles. A fundamental cause of these failures is an inadequate selection of the cementitious adhesive. Adhesive performance is usually evaluated upon the bases of early age behaviour. The knowledge of this behaviour is essential for classification and labelling, however it gives no indication of long term service life performance. Objective test methods that can evaluate the building system and its components performance throughout its service life are lacking. At Faculdade de Engenharia da Universidade do Porto's (FEUP) Building Physics Laboratory - LFC, about 40 samples were submitted to more than one hundred accelerated aging cycles. This studys main goal was to evaluate the durability of the tile/cementitious adhesives system. This was done in terms of relating the decreasing performance (the influence of types and classes of cementitious adhesives and the tiles absorption coefficients) to the tensile adhesion strength and establish criterion of long-term performance; i.e. the selection of the most adequate adhesive for an external ceramic wall tileing systems.