Fresh properties and characteristic testing methods for alkali-activated materials: A review

Alkali-activated materials (AAMs) are increasingly popular as ecofriendly and sustainable construction materials due to their ability to reduce carbon emissions and utilize industrial byproducts. However, their practical application is currently hindered by variability in their intrinsic properties during the early stages, which affects their handling, placement, and early age performance. This study aims to provide an overview of the fresh properties of AAMs, focusing on workability, rheology, setting behavior, and heat flow. The influence of material composition on the workability and setting of AAMs is presented, and characterization methods for workability, heat flow, and early microstructure are highlighted. The workability of AAMs depends on various factors, including mix design, precursor composition, alkali activator concentration, and aggregate size. AAMs exhibit a fast setting time due to enhanced alkali activation, and the heat release during hydration is influenced by the precursor type and curing temperature. This study discusses the current limitations of fresh AAMs and provides future perspectives for research. To address these limitations, the authors propose data fusion from various experimental results and image-based analysis of the microstructure of fresh AAMs. Overall, this study contributes to a better understanding of AAMs and offers valuable insights for sustainable construction applications.