Enhancing the rheology, reaction kinetics and early-age strength of limestone calcined clay cement (LC³) with sodium silicate addition

The effect of small-dose sodium silicate (SS) solutions with varying compositions on the rheology and early-age strength of limestone calcined clay cement (LC³) was evaluated. SS addition reduced colloidal interactions in LC³, leading to significant reductions in initial yield stress and viscosity, depending on composition. All SS-added systems met the initial setting time requirements of EN 197–1. A solution containing 1 % Na₂O and a silicate modulus of 0.4 notably accelerated silicate and aluminate reactions in cement clinker, as well as synergistic reactions between calcined clay and limestone. This resulted in 1-day strength gains of 120 % and 13 % compared to LC³ and CEM I, respectively. Microstructural analysis revealed a denser matrix and refined pore structure at 1 day, consistent with accelerated phase evolution. These results demonstrate that well-formulated SS solutions can significantly enhance both rheology and early-age performance of LC³, supporting their use as effective accelerators in sustainable cement systems.