Alkali-activated materials without commercial activators: a review

Alkali-activated materials (AAM) are crafted to address escalating environmental concerns by utilizing low-carbon industrial waste, thus satisfying the need for innovative alternatives to conventional Portland cement (PC). However, the sustainability profile and cost-effectiveness of AAM depends significantly on the choice of commercial activator, with the high carbon footprint and cost of the activator serving as significant obstacles that limit the utilization of the AAM large-scale construction projects. Some locally available agricultural or industrial alkaline wastes have been researched as activators to activate other materials for AAM preparation, fundamentally eliminating AAM's activator-related drawbacks. All-waste alkali-activated materials (AWAAM) not only solve the issue of alkaline waste disposal but also exhibit satisfactory mechanical properties, along with environmental and economic advantages. This paper provides a comprehensive overview of the current phase of cementitious materials that do not require additional commercial alkali sources and are prepared entirely from waste materials, which is AWAAM. It describes the sources of alkaline wastes, elucidates the principles of synergistic interactions between these materials, explores the enhancement of AWAAM, and evaluates the cost, environmental impacts, and ionic leaching behaviors of AWAAM. Nevertheless, numerous studies have not examined the durability, leaching of hazardous materials, and workability of AWAAM.