Compressive strength of core specimens drilled from concrete test cylinders

Abstract

The compressive strength of concrete is highly influenced by the properties oftest specimens, such as size and moisture content. This paper presents theresults of compression tests on more than 650 test specimens made with fourdifferent concrete types, which are mainly air-entrained. The differences incompressive strength between different types of concrete specimens wereinvestigated with similar compaction and curing conditions. The tested speci-mens were 50×50 mm, 80×80 mm, 100×100 mm, and 150×300 mm cores,which were drilled from the cast cylinders. In addition, 150-mm cubes,100×100 mm and 150×300 mm cylinders were included in the test pro-gramme. The ratios of compressive strength between different core sizes andcore strength comparability to the cast specimens were found to be stronglydependent on the concrete type. Drilling was found to have a clear weakeningeffect on obtained compressive strength. The conversion factors for the com-pressive strength between the core and the same size cast specimen was pro-posed for 150×300 mm and 100×100 mm specimen sizes.