Evaluation of the moisture influence on compressive strength of concrete hollow blocks

Abstract

This project proposes to conduct a study on the degree of moisture influence on the concrete block at the moment of compressive strength test. The concrete hollow blocks are masonry elements broadly used in Brazil, and it is essential to have quality control of the material, especially when it is used for structural masonry. This quality control is carried out through standardized procedures, which aim to obtain reliable estimates of the actual characteristics of the material. To ensure that the procedures are adequate, there should be no uncertainty about the theoretical basis of such standards, especially regarding the repeatability of the tests. Therefore, they should be based on results from multiple sources, performed under similar conditions, which point to the same result. The series of changes in the Brazilian standard NBR 12118 in the last years, caused by changes in interpretation on the subject of the influence of block moisture in the result of compression test, motivated the development of this project. To evaluate the influence of moisture in concrete blocks, they will be tested under different relative humidity ranges and through different methods of drying. Finally, there will be a statistical analysis to evaluate the possible dependencies between the test parameters. In addition, recently it has been proposed the use of a dry capping made of wood fiber plate for compressive strength tests of concrete blocks, greatly facilitating the test. In this project, it is also proposed the use of this dry capping, beyond the usual cement paste capping and the use of grinding, to a final validation. It is noteworthy that the Bloco Brasil association supports this project, having committed to the donation of the concrete blocks. (AU)