Effect of specimen and crack sizes, water/cement ratio and coarse aggregate texture upon fracture toughness of concrete

Synopsis Tests were performed on cement mortar and concrete beams, in two stages, with a view to studying the influence of several specimen and mix variables upon the fracture behaviour of concrete. On the basis of the results from the first stage of tests, in which a single water/cement ratio and type of coarse aggregate were used, a simple formula was established to estimate the fracture toughness of concrete in terms of specimen dimensions, maximum aggregate size and notch depth, together with the mix compressive strength and modulus of elasticity (determined from separate standard cylinder tests). It was found to predict, with sufficient accuracy, the results from the second stage of tests in which, besides variation of the type of coarse aggregate and water/cement ratio, some of the specimen sizes were outside the range used in the first series.