Alkali-Activated Calcined Clay for Sustainable Construction

The cement industry is undergoing a profound transformation in response to the urgent demand for sustainable binders. Alkali-activated materials (AAMs) offer a promising pathway for manufacturing low-CO 2 concrete, demonstrating favorable mechanical and durability characteristics. However, supply chain concerns over conventional precursors have led to significant interest in calcined clays. To date, most research on alkali-activated calcined clays (AACCs) has focused on high-purity metakaolin, providing fundamental insight on its performance. Yet, the high cost and water demand of metakaolin-based AAM concrete limit commercial use. Calcined lower-grade kaolin clays are uniquely positioned to serve as AAM precursors due to their intrinsic reactivity and the widespread abundance of kaolin clay. This review explores recent developments in AACC technology with a focus on calcined lower-grade kaolin clays, highlighting key research gaps in the areas of minimum amorphous content, rheology, efflorescence, and admixture compatibility. Addressing these gaps is essential to advancing calcined clay-based AAMs for next-generation infrastructure.