Effects of Triethanolamine-Gallate on the workability, hydration and microstructure of steel slag supplementary cementitious materials

Abstract

Widely used hydration promoters primarily improve the early strength of steel slag supplementary cementitious materials (SCMs) but offer limited enhancement to later strength and fail to mitigate early hydration inhibition by steel slag (SS). This study introduces a novel organic hydration promoter, Triethanolamine-Gallate (TG), synthesized by modifying gallic acid with triethanolamine. TG imparted hydrophobicity to the SS composite cement powder, enhanced fluidity and increased initial and final setting times, and moderated hydration rate but improved overall hydration efficiency of SS composite cement. At 28d, the compressive strength of PS-TG-0.05% (PS was 70% PC and 30% SS) mortar was 21.1% and 13.3% higher than that of PS-Control and PS-TEA-0.05% mortar, respectively. TG promoted the transformation of C₃S, C₂S, C₄AF, Ca₂Fe_xAl_2-xO₅ and CaCO₃ into more C-S-H and Mc (monocarboaluminate), especially the new iron-containing Mc. TG also significantly refined the pores and reduced the cumulative pore volume of the SS composite cement.