effect of fiber on mechanical properties and toughness of self-compacting concrete exposed to high temperatures

The weakness of concrete in tension and its brittleness under various types of loadings has resulted in using different and convenient fibers, including steel and poly propylene, which in addition increasing of ductility and improvement in post-cracking behavior of concrete, have a major role in minimizing shrinkage and thermal cracks. in this study, the effects of high temperatures (200, 300, 400 and 600 ͦ c) on compressive strength, splitting strength, flexural strength and energy absorption capacity or toughness of self-compacting concretes containing steel, polypropylene and polyethylene terephthalate (pet) fibers were evaluated. the test results on fresh concrete imply that the increase in fibers make some criteria of self-compacting concrete unachievable. compared to the unheated non-fiber specimens (scc2), increasing temperature up to 600oc decreased compressive strength at steel, polypropylene and pet fiber containing specimens 30, 37.5 and 34.5%, respectively. however, residual strengths were 22, 8 and 13% higher than the heated non-fiber specimens. at 600 oc, flexural toughness and maximum flexural load were 5 and 1.8 times higher than control specimens. adding fibers had a positive effect on specimens’ explosive spalling so that spalling threshold was shifted to higher temperature levels. the proposed relationships and models at the elevated temperature are compared with experimental results. these results are used to predict more accurate and general compressive and splitting strengths, flexural strength, elasticity modulus, flexural load peak-point and flexural deflection relationships.