Further understanding of cement complexation activation: Synergistic interaction between diethanol-isopropanolamine and thiocyanates

This study investigates the synergistic interaction between diethanol-isopropanolamine (DEIPA) and thiocyanates (NaSCN, Ca(SCN) 2 , NH 4 SCN) in enhancing the compressive strength of cement mortars through multi-scale analyses, including hydration calorimetry, XRD, TG-DTG, MIP, and ICP-AES. Results show that the combination of thiocyanates (0.05%-0.50%) with 0.015% DEIPA significantly improves the 3 d and 28 d strength of cement mortars. The optimal enhancements are observed with 0.50% NaSCN (8.4 MPa increase at 3d) and 0.05% NH 4 SCN (11.2 MPa increase at 28d) in the presence of DEIPA. Strength enhancement correlated positively with dosage of thiocyanates at 3 d but negatively at 28 d. The enhancement mechanism involves accelerated hydration and pore structure refinement, as indicated by higher bound water, CH contents, and reduced capillary porosity. Thiocyanates are found to enhance clinker dissolution through metal ion complexation without hindering hydration products formation. However, co-precipitation experiment confirms that thiocyanates synergize with DEIPA to strongly inhibit AFt formation, while exerting a negligible influence on C‑S‑H precipitation. Therefore, precise dosage control is essential when utilizing thiocyanates as cement additives or concrete admixtures. The findings advance the mechanistic understanding of the synergistic effect between thiocyanates and DEIPA in enhancing cement strength, paving the way for enhancing the mechanical performance of cement-based materials.