Acid resistance of alkali-activated binders: a review of performance, mechanisms of deterioration and testing procedures

Acid resistance is an increasingly important property for cementitious materials due to the wide range of applications where they are exposed to aggressive acidic environments. These include sewage systems, agricultural environments, food industries, oil wells, acidic precipitation and many more. Conventional Portland cement-based binders are known to be susceptible to acid attack due to the chemical nature of their main hydrated phases (i.e. C-S-H, Ca(OH)₂, AFm and AFt). Alkali-activated binders are low carbon alternatives and have the potential to reduce the carbon footprint of the cement and concrete sectors. To date, wide scale uptake of alkali-activated binders has been limited. One area where they have appeared to demonstrate superior performance to traditional PC-based binders is that of acid attack. This paper critically reviews recent advances with regards to the acid resistance of alkali-activated binders. The mechanism of attack by a wide range of organic and inorganic acids is also compared. The effect and relevance of the adopted test procedures are also examined. Finally, some future research opportunities in the area are identified.