Biaxial flexural strength of concrete by two different methods

The biaxial flexural strength of a concrete panel can be evaluated by two different methods: the centrally loaded round panel test (ASTM C 1150) and the recently proposed biaxial flexure test (BFT). Twenty-six tests, with 13 specimens for each test method, were performed to verify the effect of the different test methods on the biaxial flexural strength of concrete. A finite-element analysis of the specimens of two test methods showed that the biaxial flexure test set-up allows a larger area with a uniform biaxial stress on the bottom surface around the centre of the specimen than the ASTM C 1550 set-up, indicating that the difference in the test results is attributable to the volume effects. The test results showed that the biaxial flexure test method gives a more reliable biaxial flexural strength with a 25% lower coefficient of variation than that from the ASTM C 1550.