Early-age reactivity of calcined kaolinitic clays in LC³ cements: a multitechnique investigation including pair distribution function analysis

Abstract

Limestone Calcined Clay Cements, LC³, allows CO₂ emissions savings up to 40%. The resulting binders have competitive mechanical performances after a week. However, the reactivity of LC³ at early ages is slow and should be improved. Here, we use a multitechnique approach to help in the understanding of early age reactivities which were measured by calorimetry, Frattini assay, and mechanical strengths. The disorder in the kaolinites was quantified by powder diffraction. Some footprints of the local disorder in the resulting metakaolin have been investigated by synchrotron pair distribution function (sPDF). It is concluded that Al-O interatomic correlation position and intensity in the sPDF of the calcined kaolinitic clays could be an additional good descriptor to follow early age reactivity. The results were complemented by ²⁷Al MAS-NMR studies. The rate of the pozzolanic reaction at early ages is governed by the particle size, surface area, and local disorder of metakaolin.

Keywords:

• Kaolinitic clays
• blended cements
• local structure
• total scattering
• pozzolanic reaction

Acknowledgements

CELLS-ALBA (Barcelona, Spain) is thanked for providing synchrotron beamtime at BL04-MSPD and Dr. Oriol Vallcorba for his help and support during the experiment.

Disclosure statement

No potential conflict of interest was reported by the authors.

Authors’ contributions

I.M.R Bernal: Formal Analysis, Investigation, Writing – review, & editing. M.A.G. Aranda: Conceptualization, Investigation, Writing - original draft. I. Santacruz: Investigation, Writing – review, & editing. A.G. De la Torre: Investigation, Writing – review, & editing. A. Cuesta: Conceptualization, Supervision, Funding acquisition, Investigation, Formal analysis, Writing - original draft.

Data availability

All synchrotron X-ray powder diffraction patterns, laboratory X-ray powder diffraction patterns, Thermal analysis, isothermal calorimetry, NMR, and PSD data analyzed in this article can be freely accessed on Zenodo at https://doi.org/10.5281/zenodo.5136556, and used under the Creative Commons Attribution license.

Additional information

Funding

PID2019-104378RJ-I00 from the Spanish government and P18-RT-720 from Junta de Andalucía are acknowledged by the financial support.