Determination of Concrete Strength By Using Small Diameter Cores and Microcores

Abstract

Strength of concrete is an important property for the quality of concrete. Compression testing of cores drilled from hardened concrete is a widely accepted method of strength determination. Estimation of concrete strength may be gained from compression tests conducted on cores having a diameter considerably less than the recommended one of 100 mm. This paper examines the results of tests applied on the 69 and 46 mm diameter small cores and 28 mm diameter microcores. A total number of 1925 cores were tested. The effects of specimen sizes for different length-to-diameter (1/d) ratios on the compressive strength of small diameter cores and microcores were analysed. The core strengths were compared with those of standard cylinder and cubes. Test results revealed that the effect of 1/d ratio of the specimen is more pronounced for small diameter cores and microcores. The coefficient of variation of strength values was noticed to be higher for 28 mm diameter microcores. It was indicated that core strength was affected by specimen sizes. Therefore, it was proposed that the size of specimen should be taken into consideration for the interpretation of the results used to convert the strengths of cores to those of standard cylinders or cubes.