Experimental and Numerical Investigation of Fatigue in Base-Rendering Mortar Used in Façades Undergoing Thermal Cycles

Abstract

Ceramic tile coating systems are widely used on building façades. Such façades generally consist of a few layers of materials such as rough cast, base-rendering mortar, adhesive layer for tiles, ceramic tiles, and grout between the tiles. Building coatings, in general, are subject to a variety of hazardous weather conditions including temperature variations which, combined with different mechanical properties of the façade material layers, produce thermal expansions and stresses in façades. Currently, studies of façade fatigue produced by such stress variations are not reported in the technical literature but it is a very important issue for construction companies and property owners. The purpose of this research is to evaluate the fatigue of the base-rendering mortar layer and estimate the life cycle of ceramic tile façades traditionally used in South American cities. The paper also presents a practical methodology based on experimental and numerical evaluations to estimate the fatigue life of base-rendering mortar under temperature transients of typical building façades. The Wöhler diagram of the base-rendering mortar is experimentally obtained and the thermal stress assessment done with finite-element models. With the alternating stress and the Wöhler diagram, it was possible to evaluate the lifetime of the base-rendering mortar layer in some façades. A case study is presented, showing critical situations where fatigue life can be just a few years, as observed in practice.