Abstract
Effective mitigation of alkali-silica reaction (ASR) is critical for producing durable concrete. The use of alumina-rich supplementary cementitious materials (SCMs) and chemical admixtures such as lithium salts to prevent expansion caused by ASR was first reported 70 years ago, shortly after the discovery of ASR in 1940s. Despite numerous investigations, the understanding of the mechanisms of Al and Li for mitigating ASR remain partially inexplicit in the case of Al, and hardly understood in the case of Li. This paper reviews the available information on the effect of Al and Li on ASR expansion, the influencing factors, possible mechanisms and limitations. The role of Al in mitigating ASR is likely related to the reduction of dissolution rate of reactive silica. Moreover, the presence of Al may alter the structure of crystalline ASR products to zeolite or its precursor, but such effect seems to be not that significant at ambient conditions due to the slow kinetics of zeolite formation. Several mechanisms for the lithium salts in mitigating ASR have been proposed, but most of them are not conclusive primarily due to the lack of knowledge about the formed reaction products. Combination of Al-rich SCMs and lithium salts may be used as an economic solution for ASR mitigation, although systematic studies are necessary prior to the applications.
Highlights
Alkali-silica reaction (ASR) is an important durability issue world-wide, which causes significant expansion and deterioration of various concrete infrastructures including dams, pavements, bridges, walls, barriers, and nuclear/power plant structures (Rajabipour et al, 2015; Sims and Poole, 2017)
Recent successful synthesis of ASR products at different temperatures resembling to those formed in concrete aggregates under accelerated and field conditions, provide a new opportunity to re-investigate the mechanisms of Al and Li in mitigating ASR (Shi et al, 2019; Shi et al, 2020a; Shi et al, 2021)
These studies confirmed the role of sole Al in mitigating ASR as previously suggested by other studies based on comparison of the ASR mitigation efficacy between Al-rich supplementary cementitious materials (SCMs) and silica fume (Aquino et al, 2001; Ramlochan et al, 2004)
Summary
Alkali-silica reaction (ASR) is an important durability issue world-wide, which causes significant expansion and deterioration of various concrete infrastructures including dams, pavements, bridges, walls, barriers, and nuclear/power plant structures (Rajabipour et al, 2015; Sims and Poole, 2017). The nature of the ASR products varies significantly depending on the composition of the pore solution, stage of ASR, and temperature (Shi et al, 2019; Shi et al, 2020a; Shi et al, 2020b) It remains unclear at which steps and by which mechanisms ASR expansion is generated (Shi et al, 2020b). Recent successful synthesis of ASR products at different temperatures resembling to those formed in concrete aggregates under accelerated and field conditions, provide a new opportunity to re-investigate the mechanisms of Al and Li in mitigating ASR (Shi et al, 2019; Shi et al, 2020a; Shi et al, 2021). This review article summaries and critically discusses the available investigations on the effect of Al and Li on ASR expansion, the influencing factors, possible mechanisms and limitations
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