Effect of post-fire lime-saturated water and water-CO2 cyclic curing on strength recovery of thermally damaged high-performance concrete with different silica contents

Abstract

This study investigates the effects of lime-saturated water and water–CO2 cyclic recuring on strength recovery of thermally damaged high-performance concretes (HPC). The HPC samples were subjected to elevated temperatures up to 1000 °C in 200 °C increments and underwent recuring. Phase assemblage and distribution, microstructure evolution, and pore structure of the HPC samples were identified. According to the results, recovered compressive strength of the HPC samples with low silica content can surpass their original strength after 600 and 800 °C exposure and recuring. In contrast, HPC with high silica content is unfavorable for strength recovery at temperatures above 800 °C because the low-calcium phases formed have low reactivity. After 1000 °C exposure, only water–CO2 cyclic recuring coalesces the disintegrated microstructure and recovers the compressive strength. Strength recovery primarily depends on healing the microcracks and large pores rather than the coarsened cement paste.

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ORCID for Ye Li: orcid.org/0000-0002-2379-5497

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