EVALUATION OF THE RELATIONSHIP BETWEEN COMPRESSIVE STRENGTH AND UPV OF HSC EXPOSED TO HIGH TEMPERATURES

Abstract

An experimental program was adopted in this study to investigate the degree of dependency on the using of ultrasonic pulse velocity (UPV) to evaluate the residual strength of concrete exposed to high temperatures as in the case of fires. This experimental program focus on the relationship between compressive strength and UPV of high strength concrete (HSC) after high temperature exposure. The tests were carried out using 100mm cubes. Three concrete mixes were used with target compressive strengths of 40 MPa, 60 MPa and 80 MPa. Totally fifty four concrete cubes were tested in this study. The specimens were divided into three groups according to their original compressive strength. Four temperature levels of 150oC, 350oC, 500oC and 700oC were adopted. Three specimens from each group were heated to each temperature level, cooled and then tested. While, six specimens from each group were tested as reference specimens without heating. The test results show that both concrete compressive strength and UPV decreased after high temperature exposure. Another observation is that at temperatures (150oC and 350oC ), the normal strength concrete (NSC) suffered higher percentage loss in strength than HSC, while the opposite stands at 700oC. Also it is observed that the UPV showed higher percentage loss than in compressive strength for both NSC and HSC at temperatures of 350oC and higher. Finally, it was found that the UPV-temperature behavior differs than the compressive strength-temperature behavior