Influence of the preparation of the cylindrical specimen surface and approach analysis on the test value of compressive strength

Abstract

The worldwide use of the axial compressive strength test makes it fundamental to identify the concrete class. However, this test presents dispersion of results which, consequently, reduces the reliability of the test. The surface of the tops of the specimens influences the values of strength measured, since the lack of flatness impairs the uniform application of the load. Different types of procedures can be used to ensure the flatness of the surfaces. Besides, there are different approaches for data analysis, namely to detect outliers. Thus, this research aimed to study and evaluate, the influence of sulfur capping, capping with confined neoprene sheet and noncapping of the test specimens, and the influence of the approach to detect outliers in order to understand the interference in the results. The sulfur cap presented the lowest dispersion values and the cap with confined neoprene sheet obtained the highest strength. In addition, the results showed that the lack of regularization of the tops of the specimens increased dispersion as it causes an important decrease of the resistance in the concrete.