Effect of the Introduction of Reactive Fillers and Metakaolin in Waste Clay-Based Materials for Geopolymerization Processes

Area of Science:

• Materials Science
• Geochemistry
• Sustainable Engineering

Background:

• Geopolymerization offers a sustainable alternative to traditional cement production.
• Clayey wastes from mining operations present a potential precursor for geopolymeric materials.
• Reactive fillers are crucial for enhancing the properties of geopolymeric formulations.

Purpose of the Study:

• To assess the role of reactive fillers (sand, waste glass powder, metakaolin) in the geopolymerization of waste clay materials.
• To evaluate the impact of these fillers on the mechanical and chemico-physical properties of the resulting geopolymers.
• To investigate the potential valorisation of halloysitic, kaolinitic, and smectitic clay wastes.

Main Methods:

• Three types of clayey wastes (halloysitic, kaolinitic, smectitic) were thermally treated at 650 °C.
• Geopolymeric pastes were formulated with 20% reactive fillers (sand, waste glass, metakaolin) and cured at room temperature.
• Analyses included chemical stability in water, microstructural variations (XRD, SEM), and compressive strength.

Main Results:

• Commercial metakaolin (MK) exhibited the highest reactivity, followed closely by sand and waste glass.
• MK and sand promoted geopolymeric gel densification, while waste glass grains induced crack deflection.
• Halloysitic clay showed the poorest chemical stability and mechanical properties; kaolinitic and smectitic clays achieved strengths below 30 MPa.

Conclusions:

• Waste clay materials can be valorised as precursors for geopolymeric materials.
• The choice of reactive filler significantly influences the geopolymerization process and final properties.
• Sand, as a waste product from clay washing, shows promise as a viable alternative to waste glass powder in geopolymer formulations.