Mechanistic insight into mineral carbonation and utilization in cement-based materials at solid-liquid interfaces

Area of Science:

• Geochemistry
• Materials Science
• Environmental Engineering

Background:

• Understanding CO2 mineralization in alkaline solid waste is crucial for effective carbon capture and utilization.
• Controlling reaction pathways and kinetics at mineral-water interfaces is key to optimizing these processes.

Purpose of the Study:

• To investigate the mechanistic understanding of CO2 mineralization and utilization reactions at mineral-water interfaces using petroleum coke fly ash.
• To characterize mineral phase changes during CO2 mineralization and assess the potential of the modified fly ash as supplementary cementitious materials.

Main Methods:

• High-energy synchrotron X-ray analyses (2D to 1D diffraction patterns) with Rietveld refinement.
• X-ray fluorescence mapping and electron microscopy for qualitative verification of reaction mechanisms.

Main Results:

• Continuous dissolution of calcium oxide (CaO) and calcium hydroxide (Ca(OH)2) in fly ash drives calcium carbonate (calcite) nucleation and growth.
• Dissolution of calcium sulfate (CaSO4, anhydrite) also contributes to calcite formation.
• Calcium sulfate in fly ash mitigates early hydration of tricalcium aluminate, preventing negative impacts on cement strength development.

Conclusions:

• The study elucidates the reaction mechanisms of CO2 mineralization in fly ash, highlighting the role of calcium dissolution.
• Petroleum coke fly ash can be effectively utilized for CO2 mineralization and as a supplementary cementitious material.
• Findings provide a basis for designing efficient reactors and cost-effective processes for CO2 capture and utilization.