Investigation of synergistic effects of lithium slag and granulated blast furnace slag from the perspectives of physics and hydration

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The combined use of granulated blast-furnace slag (GBFS) and lithium slag (LS) as supplementary cementitious materials (SCMs) within the ordinary Portland cement (OPC) improves the 28-day mechanical property. This study investigated the interaction between the two SCMs to reveal their synergistic effects, focusing on aspects such as packing density, hydration space, and hydration reaction. A novel method that combined the water film thickness (WFT) theory and particle size analysis, has been developed to characterize the pre-hardening hydration space of the paste. The hydration reaction was elucidated through phase analysis, ion dissolution, microstructure of hydration products, and micro-pore structure. The synergistic effects can be attributed to the filler effect, optimal hydration space availability, and changes in the quantity and microstructure of C-(A)-S-H gel products. With increasing LS content in the ternary system, there was an augmentation in Al3+ dissolution, facilitating the transition from C–S–H to C-A-S-H, and curtailing Ca2+ dissolution. Concomitantly, the microstructure of C-(A)-S-H gels shifted from fibrous forms to spherical clusters. Incorporating both GBFS and LS not only increased gel pore porosity but also complexified the spatial configuration of gel pores. A peak in 28-day compressive strength was observed at an OPC/GBFS/LS blend ratio of 70 %:15 %:15 %. This was attributed to the peak of WPD, an appropriate unit initial interparticle void volume, increased gel products, and the intricate spatial reticulation of C-(A)-S-H gels.