Abstract
In recent years, the construction industry has striven to promote environmentally friendly materials. A growing body of literature has recognised fly ash-based geopolymers as a promising alternative to Portland Cement. However, a detailed and in-depth review specifically concerning high-temperature exposure and fire resistance of fly ash-based geopolymers is still missing. This review provides a comprehensive summary on the recent research progress concerning mix design, curing and their effects on thermal and fire resistance of Class F fly ash geopolymers. Due to the wide variety of characteristics, the performance of class F fly ash is recommended to be assessed in terms of its reactive phases. The influence of different alkali sources and their effects on thermal resistance are discussed, showing that potassium-based activators contribute to better performances. By applying Factsage calculations, the role of minor elements in controlling melting temperature and phase formation as well as the mechanisms behind the initial strength increase of fly ash-based geopolymers during heating are discussed. Moreover, the evolution of material properties during high-temperature exposure and the key parameter pore interconnectivity to avoid damage such as spalling is reviewed. Finally, recommendations for further investigations are provided.
Highlights
Increasing attention is being paid to the issue of fire resistance of building materials and the associated safety aspects, which are espe cially motivated by the numerous fires in residential buildings and public infrastructure
This review summarizes the comprehensive studies conducted dur ing the last decades regarding Class F fly ash geopolymers for hightemperature and fire- applications
The research on the suitability of FA-based geopolymer for high-temperature application should be based on the reactive phases of fly ash
Summary
Increasing attention is being paid to the issue of fire resistance of building materials and the associated safety aspects, which are espe cially motivated by the numerous fires in residential buildings and public infrastructure. Geo polymers, often described as anti-spalling materials [8], are produced from the reaction of an alkali source with inorganic precursors con taining alumina and silica [9]. Geopolymers for high-temperature applications have been widely investigated owing to the growing awareness of the importance of passive fire protection of buildings and structures, as well as the demand for cost-effective and environmentally friendly con struction materials [11,12,13,14,15,16,17,18]. A new comprehensive review with the focus on these items may help in understanding the interdependence of factors, the sensitivity of the geopolymer system to the action of high temperature and fire, and provide insight on the mix design for such applications. Apart from highlighting the unique properties of fly ash geopolymers for high-temperature ap plications, perspectives on features that could be enhanced, and areas of research still need to be explored are provided
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