Assessing the Relationship between the Compressive Strength of Concrete Cores and Molded Specimens

There is no universal relation between the compressive strength of cores drilled from concrete elements and molded cylinder and cube concrete specimens. The strength of concrete cores depends on several parameters. The strength correction factors account for these parameters. In this study, the effects of diameters, length to core diameter ratio (λ=L/D), test age, and coring orientation on the compressive strength of cores were analyzed with respect to the molded cylinder and cube concrete specimens. According to the test results; the compressive strength changes in 100 and 75 mm diameter cores were found to be more significant and reliable compared to those of 50 mm diameter cores. The strength decreased by 10% and 6% in 100 and 75 mm diameter cores drilled perpendicular and parallel to the direction of casting due to drilling damage. The compressive strength of cores with λ=1.0 was equivalent to 92% of that of cores with λ=2.0. Furthermore, it was found that the cores drilled perpendicular to the direction of casting and having a λ=2.0 ratio was 83% and 71% of that of 28-day standard cylinder and cube, respectively. The correction factors between cores and standard cylinder and cube specimens were determined to assess the in-site compressive concrete strength.