Synthesis and use of different CaCO3 in Portland cement

Xu, Yaowen, Chua, Guan Feng, Zhao, Mingshan, Mo, Liwu and Jin, Fei ORCID: https://orcid.org/0000-0003-0899-7063 2025. Synthesis and use of different CaCO3 in Portland cement. Presented at: RYS2025 1st RILEM Youth Symposium, Online, 20-21 October 2025. Item availability restricted.

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Abstract

Calcite has been extensively used in blended cement, whereas the effects of other CaCO3 forms remain underexplored. Due to their distinct thermodynamic properties, different forms of CaCO3 may influence the reaction mechanisms and hydration behaviour in blended cement systems. This study synthesised various forms of calcium carbonate (CaCO3), including calcite, aragonite, vaterite, and amorphous calcium carbonate (ACC), and investigated their dispersion behaviour in Portland cement (PC) pastes, as well as their effects on cement hydration. The drying method was found to critically influence the phase stability of the synthesised CaCO3: oven drying at 50 °C preserved calcite and aragonite, whereassolvent exchange with acetone was required to retain vaterite and ACC. Dry CaCO3 powders exhibited a tendency to agglomerate during mixing, resulting in visible deposits in hardened pastes. To address this, a wet-mixing method using the freshly synthesised CaCO3 slurry was developed, significantly improving homogeneity. Isothermal calorimetry revealed that all crystalline forms of CaCO3 accelerated early-stage cement hydration, while ACC induced a retardation effect. Moreover, the use of fresh calcite slurry led to enhanced hydration compared to dried powders, likely due to increased calcium ion availability. These findings highlight the importance of CaCO3 form, processing conditions, and incorporation method in optimising the performance and sustainability of blended cement systems.

Item Type:	Conference or Workshop Item (Paper)
Status:	In Press
Schools:	Schools > Engineering
Funders:	EPSRC
Date of First Compliant Deposit:	7 October 2025
Date of Acceptance:	5 October 2025
Last Modified:	10 Oct 2025 13:30
URI:	https://orca.cardiff.ac.uk/id/eprint/181507

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