Utilization of Waste Catalysts in Cementitious Materials

Industrial processes such as petroleum refining generate vast quantities of spent catalysts rich in aluminosilicate and zeolitic phases. Rather than consigning these residues to landfill, researchers have demonstrated their value as supplementary cementitious materials or as components in alkali-activated binders and geopolymers. When finely milled and appropriately pretreated, waste catalysts can exhibit significant pozzolanic reactivity, consuming calcium hydroxide and forming additional calcium silicate hydrate (C–S–H) and related gels. The net effect is twofold: reduction of Portland cement demand and immobilisation of potentially harmful metals within a stable cementitious matrix. Applications span low-carbon blended cements, multi-component binders with rapid early strength gain, and non-sintered bricks activated with alkali salts. Advances in thermal or chemical activation—such as NaOH or Na₂CO₃ fusion—further enhance the dissolution of silica and alumina, promoting denser microstructures and improved mechanical properties. On a global scale, this approach contributes to circular economy objectives, mitigates the environmental footprint of construction, and offers novel routes for valorising petrochemical by-products.

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Utilization of Waste Catalysts in Cementitious Materials publication trend

The graph below shows the total number of articles in utilization of waste catalysts in cementitious materials across all publications each year (not limited to Nature Index journals).

Technical terms

Fluid catalytic cracking (FCC) catalyst: A zeolite-based aluminosilicate residue from petroleum refining, valued for its pozzolanic behaviour when finely ground.

Pozzolanic reactivity: The chemical affinity of silica- and alumina-rich materials to react with calcium hydroxide, forming cementitious hydrates such as C–S–H gel.

Alkali activation: A cement manufacturing route in which aluminosilicate precursors are activated by high-pH solutions (e.g., NaOH, Na₂SiO₃) to generate binding phases without traditional clinker.

Calcium silicate hydrate (C–S–H) gel: The primary binding phase in hydrated cement, responsible for strength and durability in cementitious composites.

References

1. Potential of spent fluid cracking catalyst (FCC) waste for low-carbon cement production. Effect of treatments to enhance reactivity. Cement (2023).
2. Hydration Processes of Four-Component Binders Containing a Low Amount of Cement. Materials (2022).
3. Assessment of the Rheological and Mechanical Properties of Geopolymer Concrete Comprising Fly Ash and Fluid Catalytic Cracking Residue as Aluminosilicate Precursor. Applied Sciences (2021).
4. Utilization of Spent FCC Catalyst as Fine Aggregate in Non-sintered Brick: Alkali Activation and Environmental Risk Assessment. Frontiers in Chemistry (2021).