Clay activation: A review

Abstract

Intensive research on alternative cements targets Portland cement’s environmental impact, with clays emerging as prime candidates due to global abundance and compatibility with performant low-carbon binders such as geopolymers and limestone calcined clay cement. However, diverse clay minerals exist and the most widely available clays remain poorly understood, with fragmented data and a lack of integrated knowledge; this hinders their optimal utilisation. This review offers clay activation fundamentals and their key role in developing sustainable cementitious binders. It go through four major pillars: I) Fundamentals of phyllosilicates and common clay impurities, before activation; II) Cutting-edge characterisation techniques for quantifying clay reactivity, spanning micro- and nano-scale experimental methods to standardised protocols, with a critical evaluation of their limitations and potential; III) State-of-the-art clay activation techniques, analysing the evolution of various clay minerals under diverse thermal, mechanical, chemical, and combined treatments from mechanistic and microstructural perspectives; and IV) Current clay activation infrastructures and their performance efficiency. This critical review systematically revisits current knowledge by comparative analyses, identifying key gaps in the field, and examining challenges in scaling activation techniques for industrial adoption, providing a framework for future research and technological advancement.