Effect of Specimen Size and Shape on Strength of Concrete

ABSTRACT: Testing the mechanical properties (especially compressive strength and tensile strength) of concrete is one of the most crucial stages of construction works. To control the quality of concrete, there are various moulds that are used for casting concrete samples during concreting works according to different standards at different countries. On the other hand, it is known that different shapes and sizes of concrete samples can cause variations in results of compressive strength or splitting tensile strength. This research concentrated on the effect of specimen sizes and shapes on compressive and splitting tensile strength of concrete, cured at different conditions and tested at both early and late ages. At the end of experimental study, hardened density, non-destructive tests (i.e. rebound hammer and PUNDIT), compressive strength and splitting tensile strength for different curing conditions were performed and some analyses were done to obtain conversion factors and relations among these factors and results. The results of analyses indicate that for all testing conditions, there is a strong influence of variation of size and shape of the specimens. In some cases, by changing the curing conditions, the change of trend of experimental results was not significant, for example the results of PUNDIT test. However, by changing testing age, there was a strong alteration in the results and their trends. Keywords: size effect, shape effect, compressive strength, splitting tensile strength, rebound hammer, PUNDIT, curing regime, conversion factors. ……………………………………………………………………………………………………………………………………………………………………………………………………………………