Recent advances in chemical admixtures for improving the workability of alkali-activated slag-based material systems

The early reaction process of alkali-activated slag (AAS) systems is much faster than that of Portland cement systems, resulting in rapid setting. Therefore, fluidity control and setting adjustment are two critical issues for practical applications of AAS; these issues are usually addressed using chemical admixtures. This paper reviews the current research progress in the field of chemical admixtures to improve the workability and setting time of AAS systems. The stability of different superplasticizers, including vinyl copolymers (V), melamine (M), lignosulfonate (LS), naphthalene (N) and polycarboxylate (PCE), in different alkaline activator solutions is summarized and is important in terms of their dispersion performance in AAS systems. The nature of alkaline activators has a significant influence on the performance of the polymers. Moreover, the effects of different superplasticizers and retarders on the workability, setting time and mechanical properties of the AAS systems are discussed. This review provides guidance for improving the AAS performance by superplasticizers and retarders to promote the application of AAS in construction engineering.