Quantitative analysis and phase assemblage of basic oxygen furnace slag hydration.

Area of Science:

• Materials Science
• Civil Engineering
• Environmental Science

Background:

• Basic oxygen furnace (BOF) slag offers a sustainable alternative for building materials, reducing CO2 footprint and solid waste.
• Current use is limited due to poor understanding of its hydraulic activity.
• Industrial waste management and circular economy initiatives can benefit from BOF slag utilization.

Purpose of the Study:

• To systematically characterize the hydration products of BOF slag.
• To investigate the influence of milling on slag reactivity and hydration.
• To understand the role of particle size in slag hydration and immobilization.

Main Methods:

• Hydration of BOF slag.
• Systematic characterization using X-ray Diffraction (XRD), Quantitative XRD (QXRD), and Scanning Electron Microscopy/Energy Dispersive X-ray (SEM/EDX) phase mapping.
• Internal consistency checks between analytical techniques.

Main Results:

• Amorphous hydration products, primarily hydrogarnets and C-S-H gel, were identified and quantified.
• Extended milling significantly enhanced reactivity, engaging all major slag phases like wüstite.
• Brownmillerite transformed into hydrogarnets within 7 days; hydration products immobilized vanadium and chromium.
• Particle size influenced C2S reaction, hydrogarnet/C-S-H gel composition and proportion, and immobilization capacity.

Conclusions:

• Developed an overall hydration reaction model for BOF slag.
• Demonstrated that BOF slag hydration yields valuable products for building materials.
• Highlighted the importance of milling and particle size for optimizing slag reactivity and immobilization properties.