Toward clean cement technologies: A review on alkali-activated fly-ash cements incorporated with supplementary materials

The consistent development of the waste-minimisation and recycling-oriented technologies in the most resource- and energy-intensive industries is crucial for sustainable development. Chemical activation based on a non-fired or low-temperature approach for the production of binders from glassy aluminosilicates, including a wide range of wastes and by-products from different industries, is an intensively developing and promising clean technology that finds application in construction and building materials, management of hazardous and nuclear waste, etc. Blended binders are designed using a mixture of mineral materials as a tool, through the regulation of composition and structure, to obtain materials with controlled performance. The resulting materials in turn improve engineering performance and aid the valorisation of different types of wastes and by-products. This is one of the main trends in the development of the modern cement industry, including the alkali activation technology. Coal fly ash is one of the large-tonnage wastes that is effectively converted by alkali activation in binders and compatible with many mineral supplementary materials. This paper reviews (i) the supplementary mineral materials of natural and waste origin from different industries for alkali activated fly ash (class F) cements (AAFA); (ii) the composition, structure, and properties formation process of AAFA incorporated with blending and modifying materials, and (iii) the feasibility for improvement of the structures and properties of mixed AAFA.