Pore pressure build-up and explosive spalling in concrete at elevated temperature: A review

Explosive spalling is a major threat to fire safety of reinforced concrete structures. A deep understanding of pore pressure build-up is important for evaluating and mitigating this unfavorable phenomenon. This paper presents a critical review on pore pressure build-up of concrete under elevated temperature. It was found that different setups were used for pore pressure measurement, which led to inconsistent results. Pore pressure build-up and explosive spalling have a positive correlation with concrete compressive strength and moisture content, heating rate, and lateral confinement. Inclusion of synthetic fiber or plant fiber increases concrete permeability and thus reduces pore pressure build-up at elevated temperature. While the addition of steel fibers alone shows limited effect on pore pressure build-up, fiber hybrid shows strong synergistic effect and results in permeability increment and reduction of pore pressure build-up. Further development on standard test method for pore pressure measurement and quantitative contribution of pore pressure on explosive spalling are necessary. Furthermore, advanced numerical model should be established to better understand fire safety of reinforced concrete structure.