Estudo da resistência de aderência à tração e ao cisalhamento de revestimentos de argamassa em substratos de concreto

• Autor(a) principal: Campos, Marina de Oliveira
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tede/6843
• topic: Revestimento; Aderência; Cisalhamento; Bond; Rendering; Shear; ENGENHARIAS::ENGENHARIA CIVIL

Bond is the crucial property of a rendering system. It is the combining result of several mortar and concrete substrates`s properties. Then, isolated studies about this subject, with single variables are insuficient. The ideal perfect understanding of the stresses, of the materials and of the tensile and shear bond sthength properties can lead to advances in the rendering system`s quality. Most of the stresses acting in rendering systems are shear stresses and, however, there is a large gap in shear bond strength knowledge. There is no standard method for the evaluation of this property. Thus, the main objective of this dissertation is to propose a laboratory method to evaluate the shear bond strength of rendering mortar in a rendering system, by the adaptation of the standartized method ASTM D 3080, used for direct shear tests in soil. Furthermore, this study aimed to evaluate the substrates`s characteristics (water cement ratio and surface roughness) and the rendering mortar`s characteristics (mix proportion) in the tensile and shear bond strength, along with doing the correlation between the two properties. In order to do so, the experimental programme included studies of tensile bond strength (Rat), using the ABNT NBR 13528 and shear bond strength studies (Rac), using the ASTM D 3080 adaptation. To the Rat tests it was prepared 10 concrete substrates that was coated with rendering mortar with 3 mix proportion (1:2:9, 1:1:6 and 1:0,5:3,4). For the concrete substrates, it was varied the water cement ratio (0,35, 0,50, 0,65 and 0,80) and the surface roughness (a smooth R1 and a roughened R2 one). For the Rac studies it was prepared 160 concrete substrates, with a smaller dimension, using the water cement ratio of 0,65. In the Rac tests the studied variables were the surface roughness (R1 and R2), the mortar mix proportion (1:1:6 and 1:0,5:3,4) and the applied normal tension (0,01 MPa, 0,06 MPa, 0,09 MPa and 0,15 MPa). Besides, it was performed an extensive characterization of the rendering mortars and the substrate`s concrete. As conclusions, the research proved that the proposed shear bond method for rendering mortar was apropriate, with low deviation coefficient of the results (6%) and with sensibility to the imposed variables (diferent mortars and substrates). The mortar mix proportion and the roughness surface of the substrates do influence in Rat and Rac, and the first one is the most influent one. The water cement ratio of the substrates concrete also influences the Rat. Besides, it was found a logarithmic correlation between Rat and Rac, with R2value of 0,87.