Estudo do ensaio de flexão em quatro pontos como método para avaliação da tensão de aderência entre chapisco e substrato de concreto

Abstract

ABNT NBR 13528 (2019) specifies the requirements for executing tensile bond strength test on inorganic mortars, both on site and in laboratory, through the test known as pull-off. This test has been subject of studies by the scientific community since it shows a high coefficient of variation in its results - around 35% - in addition to being susceptible to variations inherent to the application of the test by the operator. The research seeks to evaluate the four-point bending test as a method for obtaining the tensile strength at the interface between roughcast mortar and concrete substrate. Roughcast was applied with a water/cement ratio of 0.65 on the lateral faces of concrete prisms and standard mortar substrate plates, which were submitted to the bending test and, with the load value in the moment of detachment of the mortar layer, adhesion strength was calculated with equations from resistance of materials. Despite the values found being higher than those found in the literature, the method proved to be effective in obtaining adherence values. Plates proved to be more suitable than prisms when evaluating adhesion due to their greater deformation potential. However, conducting more accurate tests is necessary, analyzing other factors that influenced these results.