Regulating the workability of NaOH-activated blast furnace slag pastes by considering the mutual inhibition between calcium-sodium aluminosilicate hydrate and hydrotalcite during precipitation

Regulating the workability of NaOH-activated blast furnace slag (NAS) pastes is essential for their effective application. Based on the mutual inhibition between calcium-sodium aluminosilicate hydrate (C-N-A-S-H) and hydrotalcite (LDH) during precipitation (MICL), a novel strategy for regulating paste workability was developed. The workability losses, including the slump loss and the setting time, occurred through hydrate formation and was controlled by the MICL mechanism. The inhibition of the LDH formation by C-N-A-S-H caused the formation of Ca-containing LDH by replacing Mg²⁺ with Ca²⁺. With moderate NaAlO₂ addition, C-N-A-S-H and Ca-containing LDH slowly formed because the difference in the degree of mutual inhibition between C-N-A-S-H and LDH during precipitation (DMICL) was minimized. Therefore, workability losses occurred slowly. However, at relatively high (low) NaAlO₂ addition amounts, the DMICL was large, and Ca-containing LDH (C-N-A-S-H) quickly formed; thus, workability losses occurred rapidly. A moderate addition of NaAlO₂ with 1 % Al₂O₃ decelerated the workability losses and increased the compressive strength.