Mechanistic study of early hydration and strength development in lithium slag cement with c-s-h-pce nanocomposites

In a high-volume (50 wt.%) spodumene lithium slag (LS)-blended cement system, a polycarboxylate ether (PCE)-stabilized C-S-H nano-seeding accelerator (C-S-H-PCE) was introduced to improve the early-age mechanical properties. The effects of C-S-H-PCE on workability, early strength, and hydration behavior were systematically investigated. The results showed that C-S-H-PCE significantly improved the early compressive strength while maintaining good workability. At a dosage of 3 wt.%, the compressive strengths at 8 h, 16 h, and 24 h increased by approximately 363%, 143%, and 65%, respectively, compared with the blank sample. Isothermal calorimetry and hydration kinetics analyses demonstrated that C-S-H-PCE accelerated early hydration, increased the heat evolution rate, and reduced the nucleation energy barrier, thereby mitigating the dilution and hydration delay effects caused by high LS content. XRD and 29Si NMR analyses further confirmed that C-S-H-PCE promoted the formation of C-S-H and C-A-S-H gels. The findings reveal that C-S-H-PCE accelerates early cement hydration, leading to higher compressive strength. Meanwhile, the increased alkalinity of the pore solution promotes dissolution of the chain-like aluminosilicate framework of LS, allowing the pozzolanic reaction to occur at an earlier age. The resulting formation of C-A-S-H gel and subsequent refinement of the pore structure further contribute to the mechanical enhancement.