Estudo do comportamento de alvenaria estrutural com juntas finas de composto polimérico

Abstract

This research aimed to evaluate the behavior of concrete block structural masonry built with thin polymer composite mortar. The construction of structural masonry with thin joints has been used for some years in Europe, and some countries already have design standards considering its application. However, there are still no standards for the design of structural masonry with thin joints made of polymeric compounds, due to the lack of knowledge about the behavior of masonry laid with this type of material. This research was developed to evaluate the behavior of masonry in compression through tests carried out on prisms, small walls and walls. A step was also developed to evaluate the influence of filling the vertical joint on the shear behavior of the masonry. The flexural behavior of the masonry was also evaluated through bending resistance tests carried out on prisms according to the procedure described in ABNT NBR 16868-3 (2020) and also using the lever method provided for in the Australian standard AS 3700 (2017). Three types of concrete blocks with a nominal size of 140x190X290 mm were used, with different values of compressive strength and also two polymeric compounds from different producers. Procedures were proposed for performing tests to characterize the mechanical properties of polymeric compounds. When performing compressive strength tests, it was possible to notice differences between the compounds from the two producers. This difference would not be perceived just by carrying out the characterization tests specified in NBR 16590-2 (ABNT, 2017); therefore, they can be used to differentiate the properties of different polymeric compounds with greater precision. The use of plastic wedges can assist in the laying process, to ensure the alignment of the rows. NBR 16590-1 (ABNT, 2017), points out filling the vertical joint as optional, however, shear resistance tests indicate that there is a decrease of around 60% in shear resistance for samples built without filling the joint vertically, indicating the need to fill it out. The tests show that the equations and expressions used for conventional masonry cannot describe the behavior of thin-joint masonry laid with polymeric compounds. For conventional masonry there is a considerable increase in the modulus of elasticity of the masonry as the compressive strength of the block used increases, however, in the case of thin joint masonry this behavior was not observed, and the modulus did not vary much with the use of blocks of different resistance levels. An equation was proposed to predict the modulus of the masonry based on the characteristics of the blocks and polymeric compounds, enabling greater precision in estimating the modulus of this type of masonry. Performance tests were carried out on wall specimens without the presence of rendering mortar or any other surface coating. The results showed satisfactory behavior for the suspended load and hard body impact tests. For the thermal shock test, moisture was observed passing to the opposite side of the wall during water spraying, indicating the need to apply a coating so that this type of masonry is capable of guaranteeing watertightness.