Determination of mechanical, physical and micro-structural properties of microcores drilled from concrete beams and reinforced concrete construction systems

Compressive strength of concrete is probably the most important single property of concrete. In-situ strength is the strength of the concrete as it exists in the construction and is the end result of the quality of concrete in the construction. The examination and compression testing of cores cut from hardened concrete is a well-established method for the determination of in-situ strength of concrete. The core diameter affects the test results significantly. Microcores offer considerable advantages in terms of reduced costs and damage. In this experimental study, various concrete mixtures were prepared by using crushed limestone aggregate having the maximum aggregate size of 22 mm. The standard cube and cylinder tests and core tests were performed on the cube, cylinder and various core specimens. The micro-structural properties of different diameter cores were examined by using Scanning Electron Microscope (SEM). On the other hand, lightweight concrete was produced by using pumice aggregate. At the end of this experimental study, 94, 64, and 28-mm (microcore) diameter cores were drilled from the members such as columns and shear walls of 17 different buildings. The in-situ compressive strengths of 94, 64, and 28-mm (microcore) diameter cores were investigated. The equivalent compressive strength values of 28 mm diameter cores drilled from columns and shear walls of the buildings were evaluated by using a statistical software. The distributions suitable for the data were determined. Finally, the probability density function was derived only as a function of the coefficient of variation, for normalized compressive strength values of micro-cores. The established probability density function which is only a function of the coefficient of variation has far reaching use in future studies concerning both applied and fundamental research.