Effect of post-fire curing and silica fume on permeability of ultra-high performance concrete

This paper investigates effects of post-fire curing and silica fume on permeability recovery of ultra-high performance concrete (UHPC). UHPC samples were heated to 200, 300, 600, and 900 degrees C. After cooled to ambient temperature, the samples were recurred in water for 28 days. Permeability, chemical composition, pore size distribution, and microstructure were measured and analyzed to reveal the post-fire curing mechanism. The results showed that permeability of the UHPC mixtures with and without silica fume decreased after 200 degrees C heating and increased after higher temperature exposure. The increase of permeability was mainly due to coarsening of microstructure and formation of microcracks. Permeability of the samples was recovered after 600 and 900 degrees C exposure and post-fire curing. The mixture without silica fume showed greater permeability recovery due to the newly formed Portlandite and C-S-H filled the fire-damaged microstructure effectively. However, with addition of silica fume, the loose Ettringite formed did not contribute to significant lowering of permeability. (c) 2021 Elsevier Ltd. All rights reserved.