A mitigation strategy to improve workability of Na2CO3 or Na2SiO3 activated slag system: Supplementation of calcium salt

Alkali-activated slag (AAS) using Na 2 CO 3 or Na 2 SiO 3 offers less corrosive alternatives to NaOH activation but suffers from severe workability limitations. To address this, we propose calcium supplementation strategy to counteract activator anion-induced Ca 2+ depletion, the primary cause of polycarboxylate superplasticizer (PCE) dispersion failure. Through assessment of workability, hydration kinetics and strength development, the compatible PCE was identified as AA-7HPEG4.5. The optimal calcium supplementation was determined to be a molar ratio of 0.75 (Ca 2+ /CO 3 2− ) for the Na 2 CO 3 -AAS system and 1:1 (Ca 2+ /SiO 3 2− ) for the Na 2 SiO 3 -AAS system. These ratios achieved an optimal balance between workability requirements and mechanical performance. It is hypothesized that this mitigation strategy may extend to other PCEs capable of operating in Na 2 CO 3 or Na 2 SiO 3 systems, provided their dispersing power in NaOH-AAS remains sufficient. However, this extrapolation is pending further experimental validation.