Cementitious Materials and Pozzolanic Reactions

Cementitious materials encompass a broad class of binders that harden and develop strength through hydration or chemical reaction. Traditional Portland cement, produced by calcining limestone and clay at high temperatures, dominates the construction industry but is responsible for a significant share of global CO₂ emissions. In response, researchers have explored supplementary cementitious materials (SCMs) such as calcined clays, fly ash and slag to replace part of the clinker phase and thus reduce the carbon footprint. The pozzolanic reaction, wherein amorphous silica and alumina react with portlandite to form additional calcium silicate hydrate and related phases, underpins the performance enhancement seen in blended systems. This reaction improves microstructural density, refines pore networks and bolsters long-term durability against chemical attack. Limestone calcined clay cement (LC3) exemplifies the synergistic use of limestone and calcined kaolinite-rich clay, achieving reduced clinker content and comparable mechanical performance. Advances in process control, from calcination temperature optimisation to mechanochemical activation, have sharpened understanding of reactivity and phase evolution. The global significance of such developments lies in scalable routes to lower-carbon cement while maintaining performance and durability targets in diverse climates and applications, from mass concrete to 3D printing materials.

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Cementitious Materials and Pozzolanic Reactions publication trend

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

Technical terms

Cementitious material: A binder that hardens by chemical reaction with water, imparting strength and durability to composites.

Pozzolanic reaction: The chemical interaction of reactive silica and alumina with calcium hydroxide, yielding strength-contributing hydrates.

Clinker: The primary nodular product of cement kilns, composed mainly of calcium silicates, whose proportion determines cement CO₂ intensity.

Portlandite (CH): Calcium hydroxide formed during hydration, which can react with pozzolans to refine the microstructure.

Metakaolin (MK): Dehydroxylated kaolinite produced by calcination, serving as a highly reactive supplementary cementitious material.

Calcium silicate hydrate (C–S–H): The principal binding phase in hydrated cement, responsible for mechanical strength and durability.

Limestone calcined clay cement (LC3): A ternary binder combining clinker, calcined clay and limestone, offering reduced carbon emissions and enhanced performance.

References

1. Reactivity of kaolinitic clays calcined in the 650 °C–1050 °C temperature range: Towards a robust assessment of overcalcination. Cement and Concrete Composites (2024).
2. Hydration and phase assemblage of limestone calcined clay cements (LC3) with clinker content below 50 %. Cement and Concrete Research (2024).
3. Life cycle assessment of limestone calcined clay concrete: Potential for low-carbon 3D printing. Sustainable Materials and Technologies (2024).
4. Clay calcination technology: state-of-the-art review by the RILEM TC 282-CCL. Materials and Structures (2021).
5. Mechanochemical activation of natural clay minerals: an alternative to produce sustainable cementitious binders – review. Mineralogy and Petrology (2019).