Artificial alkali-activated aggregates developed from wastes and by-products: A state-of-the-art review

Natural resources depletion is gradually becoming a critical burden on the environmental and ecological balance, pushing the development of artificial aggregates forward. In order to curb the shortage issues of natural aggregates and minimize the destruction of land topography, alkali-activated aggregates (AAA) have gradually become a hot topic in recent years as a new application of alkali-activated materials (AAM) with the benefits of utilizing industrial by-products and waste materials. This article provides an overall review of the manufacturing process and engineering properties of two types of artificial aggregates, cold-bonded AAA (CB-AAA) and sintered AAA (ST-AAA). Their applications in concrete, besides the mechanical evaluation, durability performance, and leaching behavior, are summarized based on the existing research outcomes. Finally, the future perspectives and challenges of artificial aggregates development are also proposed.