Effect of High Elevated Temperatures on the Compressive Strength and Ultrasonic Pulse Velocity of High Strength Concrete

Abstract

In this study, the effect of fire on the compressive strength of high strength concrete (HSC) is investigated. Two different tests, one of them is the non destructive test which is the ultrasonic pulse velocity (UPV) test and the other is the destructive compression test, are carried out using (10cm) cubes. Forty-five cubes (one third of them are of normal strength concrete (NSC) with original strength of (52.67 MPa) and the other two thirds are of (HSC) with original strength of (61.04 and 72.33 MPa), respectively, are heated to temperature levels of (200, 400, 600, and 800°C). Then after specimens are air cooled and (UPV) test is done, the specimens are destructively tested. The results indicated that, the residual compressive strength after high temperature exposure of the (NSC) is higher than that of (HSC),for example, the residual compressive strength after exposure to temperature level (800°C) for the former is (39.5%) while for the later is(19.5%) at worst case from their original strength. Also, the compressive strength reaches its peak value in the (NSC) earlier than the (HSC). Statistical analysis is made to find mathematical relationships to relate the results of the destructive test with that of non destructive test for both the (NSC) and (HSC), also to relate the results of (HSC) with that of (NSC).