Effects of specimen sizes and loading rates on compressive strength of concrete

Abstract

Concrete can arguably be attributed as the most commonly used material in the building construction industry. It is crucial that the concrete properties can be measured accurately in order to confirm the consistency in quality of a specific concrete batch mix. Compressive strength tests provide a good and straightforward indication of determining the property of the concrete in its hardened state. Specimens of concrete of various shapes and sizes are used for determining the compressive strength of the concrete. Conformance to the national standards predominantly dictates the shape and size of the specimen used to determine compressive strength of concrete. In research and teaching laboratories, the availability of specimen moulds may also have an effect on the size and shape used for determining various properties of concrete. These comparisons may also be beneficial in demonstrating and reinforcing properties of concrete in lab conditions to students undertaking engineering programmes. As part of an inter-related series of studies, an experimental study was done to determine the effects of differences in concrete properties using specimens of different sizes and at different loading rates. Compressive strengths at various ages were determined for concrete specimens of different sizes. Results obtained to date show significant differences in the compressive strength results due to specimen size and minor differences due to different loading rates. The differences were attributed to various factors including concrete strength, mix proportions and loading rate. This paper presents the results of findings of this part of the study, as well as a literature comparison with studies of similar nature.