Behaviour of alkali-activated concrete at elevated temperatures: A critical review

Abstract

Alkali-activated concrete (AAC) is recognised as a novel sustainable construction material to substitute Portland cement concrete with superior thermal and mechanical performance. However, AAC would suffer significant deterioration when subjected to elevated temperatures due to different damage mechanisms, including thermal incompatibility caused by different thermal coefficients between matrix and aggregates, pore pressure build-up and phase transformation. This paper presents a systematic and comprehensive review on the behaviour of different types of AAC such as alkali-activated fly ash, alkali-activated slag, alkali-activated metakaolin and alkali-activated fly ash-slag systems at elevated temperatures in terms of phase stability and microstructural evolution as well as thermal and mechanical performance. The effective strategies for improving the high-temperature resistance of AAC are reviewed and discussed from the perspectives of AAC matrix, aggregates and fibre incorporation, with special focus on how these strategies can tackle different damage mechanisms. This paper summarises the recent advances in the field and identifies the remaining challenges and opportunities for future research.