The effect of testing conditions (hot and residual) on fracture toughness of fiber reinforced high-strength concrete subjected to high temperatures

This paper presents experimental work on the fracture toughness of fiber reinforced high-strength concrete subjected to high temperatures. Bending and fracture energy tests were conducted during and after cooling (i.e. hot and residual tests). It was observed that bending strength for the residual tests is higher than that for the hot tests because of the effect of tensile stresses arising in concrete which occurs in the hot tests but does not occur in the residual tests. Also it was observed that fracture toughness of steel fiber reinforced high-strength concrete in the hot tests is lower than that in the residual tests. However, steel fiber reinforcement is efficient in maintaining bending strength, and is more importantly effective in improving fracture toughness of high-strength concrete during and after cooling. Thus, the hot test should be conducted for evaluating mechanical properties of high-strength concrete due to its severity compared to the residual test.