Hydraulic Activity and Microstructure Analysis of High-Titanium Slag

Area of Science:

• Materials Science
• Geochemistry
• Civil Engineering

Background:

• High-titanium slag is a byproduct of titanium production.
• Understanding its hydration activity is crucial for potential applications, such as supplementary cementitious materials.
• Blast furnace slag is a known material with significant hydration activity.

Purpose of the Study:

• To elucidate the relationship between the hydration activity and microstructure of high-titanium slag.
• To compare the hydration characteristics of high-titanium slag with blast furnace slag.

Main Methods:

• Hydration activity determination.
• Mineral phase and microstructure analysis using X-Ray Diffraction (XRD), Scanning Electronic Microscope (SEM), Fourier Transform Infrared spectroscopy (FTIR), Raman spectroscopy, and Nuclear Magnetic Resonance (NMR) spectroscopy.
• Characterization of glass phase and blast furnace slag microstructures.

Main Results:

• Slow-cooled high-titanium slag contains approximately 98% hydration inert minerals and less than 2% glass phase, resulting in hydration activity less than 25% of blast furnace slag.
• Water-quenched high-titanium slag has 98% glass phase, but its microstructure differs from blast furnace slag.
• The glass phase in high-titanium slag features stable TiO4 monomers, O-Ti-O units, and some 6-coordinated Ti4+, leading to more stable silicate structures (disilicates, chain middle groups) and a relative bridge oxygen number of 0.2, limiting its hydration activity to less than 37% of blast furnace slag.

Conclusions:

• The microstructure of the glass phase in high-titanium slag, particularly the presence of stable titanium-oxygen units, significantly hinders its hydration activity.
• Both slow-cooled and water-quenched high-titanium slags demonstrate considerably lower hydration activity compared to blast furnace slag.
• The findings suggest limitations for direct use of high-titanium slag as a standalone supplementary cementitious material without further processing.