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This paper investigated whether residual bond strength between GFRP reinforcement and concrete stabilizes immediately after cooling from elevated temperatures or continues to evolve over time. Pull-out tests were conducted on sand-coated vinyl ester bars embedded in concrete cubes exposed to 100, 200 and 300°C. Specimens were tested 24 hours, 7 days and 14 days after cooling to assess elapsed time effects. Results showed elapsed time effects depended on temperature. At 100°C, no immediate reduction was observed: 9.91 MPa (control) and 9.90 MPa after 24 hours, increasing to 11.04 MPa after 7 days. At 200°C, strength dropped from 9.91 to 7.81 MPa, then recovered to 8.87 MPa (7 days) and 9.64 MPa (14 days), approximately 87% recovery of initial loss. At 300°C, values remained stable between 7.77-7.98 MPa over 14 days. These findings indicate residual bond strength depends on both maximum temperature and time after cooling. They do not contradict existing literature on detrimental effects of elevated temperature on GFRP-concrete bond performance, but suggest reported residual strength may represent a transient post-cooling stage rather than a fully stabilized condition. Accordingly, timing of post-fire bond assessment is critical.
| Topic Area | Fatigue, Corrosion and Structural Integrity of Engineering Structures and Mechanical Systems |
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