Study on the performance of cement composites using composite-activated coal gangue

Area of Science:

• Materials Science
• Civil Engineering
• Geochemistry

Background:

• Portland cement production has significant environmental impacts.
• Industrial solid wastes like coal gangue and red mud present disposal challenges.
• Utilizing these wastes in cementitious materials offers a sustainable solution.

Purpose of the Study:

• To investigate the feasibility of using thermally activated coal gangue as a partial Portland cement replacement.
• To evaluate the effects of composite activation using red mud and sodium silicate on cementitious properties.
• To understand the hydration behavior and microstructural development of these novel materials.

Main Methods:

• Orthogonal experimental design.
• Isothermal calorimetry, low-field nuclear magnetic resonance (LF-NMR), X-ray diffraction (XRD), and scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS).
• Compressive strength testing at various curing ages.

Main Results:

• Sodium silicate delayed hydration kinetics and broadened exothermic peaks.
• LF-NMR indicated sustained water consumption in sodium silicate systems.
• Red mud helped regulate hydration and partially offset strength loss from coal gangue.
• Combined red mud and sodium silicate activation yielded lower compressive strength than sodium silicate alone.
• Co-activated systems showed heterogeneous microstructures and less compact formations.

Conclusions:

• Composite activation with red mud and sodium silicate influences hydration and microstructure.
• The combined activation strategy resulted in reduced mechanical performance compared to sodium silicate activation alone.
• This research provides insights into optimizing activation strategies for coal gangue-based cementitious materials and promotes industrial solid waste utilization.