Rheology of alkali-activated materials: A review

Many alkali-activated materials (AAMs) exhibit poor workability in mixing owing to great viscosity of the paste and fast setting. Chemical admixtures commonly used in Portland cement-based materials, such as rheology control additives and superplasticizers, show lower efficiency in AAM systems. Understanding the rheological features of various AAMs and their control can lead to a valuable guidance for their application in large-scale, especially in the field of pumping and placement, grouting and 3D printing, etc. This paper aims to deliver a comprehensive review of the effects of composition factors including activators, precursors, admixtures, additions, aggregates and fibers on the rheology of AAMs, as well as models for describing their rheological behavior. The current progress has shown that the large knowledge gap needs substantial research from scientific mechanisms to robust formulations of paste, mortar and concrete to meet both workability and mechanical requirements.