A review on the effects of chemical admixtures on alkali activated concrete

Abstract

Alkali activated concrete (AAC) is a cement-free concrete and widely accepted as a construction material by researchers due to its high strength, durability, raw material availability, low construction cost and energy cost. Nevertheless, the main issues associated with the practical implementation of AAC are high shrinkage, low workability and quick setting behaviour. The use of chemical admixtures is the only solution for improving the workability of AAC, and it modifies the properties of concrete. The behaviour of admixtures in conventional concrete and AAC are different. Hence it is essential to conduct a detailed literature survey for finding the suitability of chemical admixtures in AAC. This review paper shows the trend of admixtures used in AAC and describes how they affect AAC's rheological characteristics, setting time, and mechanical properties. From the review, it is clear that the use of admixtures in AAC mainly depends on the activator solution used, type of binder, type and dosage of admixtures and the need for the admixtures in concrete. The investigations related to the effects of admixtures in AAC are continuing globally. PCE and SNF- based superplasticizers are generally recommended for AAC, with PCE suited for low alkaline AAC and SNF for high alkaline AAC. Lignosulphonates also show good compatibility with AAC, but their effects for improving the mechanical behaviour in AAC are lesser than SNF.