Effect of Ethanol-diisopropanolamine on the Hydration and Mechanical Properties of Steel Slag-cement Composite System

Abstract

Steel slag as a solid waste during steel-making has potential cementitious activity, and its use as supplementary cementitious material is an effective way to improve its resource utilization. Ethanol-diisopropanolamine (EDIPA), as an organic admixture, affects the hydration of the steel slag-cement composite system. In this paper, the effect of EDIPA on the hydration and mechanical properties of the steel slag-cement composite system was investigated by using mortar strength tests and combining with heat of hydration, X-ray diffraction (XRD), thermogravimetry/differential thermogravimetry (TG/DTG), scanning electron microscope (SEM) and other testing methods. The results show that EDIPA can improve both early and late compressive strength of steel slag-cement mortar at low dosing (0.02%). However, at high dosing (0.06%, 0.10%), EDIPA is unfavorable to early strength, but enhanced late strength more strongly than low dosing. Low dose of EDIPA can promote the hydration of steel slag-cement composite pastes, and can also improve the hydration degree in the early and late stages. At low dosing, EDIPA can promote the formation of ettringite (AFt) and facilitate the transformation from AFt to monosulfoaluminate (AFm). In addition, EDIPA affects the crystal structure and morphology of Ca(OH)₂ prepared by co-precipitation method. And the morphology of Ca(OH)₂ gradually changes from long hexagonal column to short hexagonal column and then to irregularly radiating lamellar with the increase of EDIPA dosing. This indicates that EDIPA inhibits the vertical growth of Ca(OH)₂ and has the reference sig-nificance for the change of Ca(OH)₂ morphology in the composite paste.