Reactivity Evolution of Mechanochemically Activated Laterite Used as a Supplementary Cementitious Material

ABSTRACT The use of laterite soil with high Al and Fe content has been investigated as a novel supplementary cementitious material (SCM) to replace traditional mineral materials for clinker substitution. High‐energy ball milling was used to mechanochemically activate laterite and change its reactivity. This reduced the particle size, decreased the amount of crystalline gibbsite and kaolinite found in the soil, and increased the proportion of reactive amorphous phase. Extending the milling time beyond 60 min produced agglomerated particles with reduced surface area. This produced excess reactive aluminum, leading to a rapid formation of a disordered protective Al‐rich layer. This hinders cement phase dissolution during early hydration and slows initial strength development. Adding 5 wt.% of gypsum effectively mitigated these effects, promoting early hydration reactions and enhancing compressive strength. The combination of intermediate milling and additional gypsum produced the optimum laterite‐derived SCM. Finally, the raw gibbsite‐rich laterite soil exhibited pozzolanic reactivity and has the potential to be used as an SCM without additional activation.