Análise numérica e experimental de revestimentos argamassados reforçados com tela frente a carregamentos térmicos cíclicos

Abstract

The facades of a building have a considerable influence on its performance, affecting aesthetics, value, and habitability requirements such as watertightness, thermal and acoustic insulation, and fire safety. Composing the so-called building envelope, the facades is characterized as the constructive system most exposed to adverse conditions and aggressive agents, being the most susceptible to the occurrence of deleterious phenomena that impair their performance. The degradation of this system has a direct and extensive impact on the quality of the urban environment, involving excessive costs for maintenance, repair, and cleaning. Mortar plaster is composed of multiple juxtaposed layers of materials with distinct characteristics, whose heterogeneous behavior can generate differential stresses that lead to cracking and loss of adhesion. To combat such occurrences, meshes are used as reinforcement elements, a technique with relatively simple execution and multiple functionalities, resulting in uniformization of stress, increase of the tensile strength and load capacity, and reduced cracking, preventing material fall in case of adhesion failure. However, there is no standardization regarding the design and execution criteria for reinforcements in the literature and regulations, which makes it difficult to use the technique due to the various variables involved in the behavior of the reinforcements, such as the depth in the mortar layer; type of material, format, mesh opening and wire thickness, among others. In this context, the present study experimentally and numerically evaluated the behavior of reinforced plaster panels exposed to cyclic thermal loads. Experimentally, the influence of three types of mesh on the thermal and mechanical properties of industrialized and mixed mortar was assessed on test specimens. The performance of these composites was also evaluated as plaster with a thickness of 3 cm and surface area of 0.50 m², varying the reinforcement depth at 0.5 and 1.5 cm, applied to masonry panels of ceramic bricks placed on concrete beams and exposed to cyclic thermal loading by radiant panel exposure and cooling with water, observing crack occurrence, geometry, and thermal gradient evolution. The numerical analysis was conducted through finite element analysis in both 2D and 3D models, replicating the experimental conditions and observing the thermal evolution, stress state, and orientation of the maximum principal stresses on the plaster surface. The results showed that the main contribution of reinforcements is the uniform distribution of stresses, controlling the initiation, propagation and opening of cracks, both during the thermal cycles and in the occurrence of shrinking. The mesh that best performed was the galvanized welded metal mesh with square opening at a depth of 1.5 cm. Recommendations for the use of mesh reinforcements are presented in the light of the results and the regulatory and technical prescriptions. It is also emphasized that the proposed numerical analysis routine is suitable for future studies in the field, using open-source software.