Post-fire behavior of bond between high strength pozzolanic concrete and reinforcing steel

This paper investigates the post-fire bond between high strength concrete (HSC) with natural pozzolan (NP) and reinforcing steel. Pullout and cube specimens were cast and cured in water at 23 degreesC for 40 days before subjected to temperatures at 600 and 800 degreesC. These were used to evaluate bond behavior and compressive strength, respectively. Post-fire cracking extent on the surface Of pullout specimens was also evaluated. In addition, empirical models were developed (based on present results) to predict the percentage reduction in bond strength. The findings indicated severe bond strength reduction of up to 24 and 74% at temperatures of 600 and 800 degreesC, respectively, accompanied by dramatic changes in the pullout load-slip behavior. HSC without NP gave the best bond performance under fire followed by HSC at NP of 10, 15 and 25% (by cement weight). Use of NP at a content of 25% had significantly improved resistance against cracking without detrimentally affecting bond strength, especially at exposure temperatures of up to 600 degreesC. (C) 2004 Elsevier Ltd. All rights reserved.