Size Effects in Model Concretes?

The paper reviews current research on the effect of specimen size on compressive, indirect tensile and flexural tensile strengths, the stress-strain characteristics, and related quantities. The measured compressive and tensile strengths were observed to increase with a decrease in specimen size in all investigations. The nondimensional stress-strain curves in compression tests were noted to be homologous for prototype and model concretes. A higher tensile-compressive strength ratio is observed in smaller specimens. The effects of duration and conditions of curing compactions, shape of specimen, and other factors are reported. Techniques are suggested to select the cylinder size to evaluate the concrete compressive strength in a model specimen. To assist with the determination of size effects and standardization, the ACI Committee 444 on Models of Concrete Structures has recommended that model investigations should include compression tests on 2-in.×4-in. (50-mm × 100-mm) cylinders along with any other cylinder sizes used.