Effect of chelation via ethanol-diisopropanolamine on hydration of pure steel slag

The low cementitious activity of steel slag (SS) limits its application in cement-based materials. The effects of ethanol-diisopropanolamine (EDIPA) on the hydration and mechanical properties of pure basic oxygen furnace SS were investigated. The hydration kinetics and pore structure of SS pastes incorporated with EDIPA and the chelation of EDIPA were analyzed to reveal the working mechanism of EDIPA. The results show that EDIPA improves the compressive strength of the hardened SS paste and greatly shortens the setting time of SS paste, which is related to the chelation of EDIPA. EDIPA could chelate with Ca2+, Al3+, and Fe3+ to form metal chelates, and the chelating ability of EDIPA to Al3+ and Fe3+ is stronger than that of Ca2+. The chelation of EDIPA simultaneously promotes the hydration and carbonation of aluminate and ferrite phases (C3A, C12A7, and C2F), resulting in a large amount of monocarboaluminate (C(A, F)CH), thus improves the hydration degree of SS paste. EDIPA could refine the pore structure of hardened SS paste, which is mainly manifested as the decrease in the amount of macropores and pore size, and the increase in the amount of small pores. The chelation of EDIPA changes the crystal structure and morphology of Ca(OH)2, which is potentially helpful to weaken the negative effect of Ca(OH)2 on strength. This study reveals the effect of chelation of EDIPA on the hydration of SS, which is a valuable guide for the resource utilization of SS.