The physics of cement cohesion: from soft colloidal gels to hardened cement hydrates

Cohesive forces develop in cement from the accumulation of multivalent ions in the water-based solution between the charged surfaces of cement hydrates and drive the setting of an initial soft colloidal gel into a progressively harder solid, a mineral glue that glues together concrete and determines its mechanics. I will discuss how the interlocking of ions and water in confinement determines the net nanoscale cohesion and links cement hydration chemistry to the emerging physical properties of the material. The resulting changes in the shape of the nanoscale forces determine the morphologies of the cement hydrate gels and ultimately the mechanics of the hardened material. I will analyze the role of spatial gradients in the development of the microstructure, similarities or differences with clay based materials and structural features that control durability and interactions with the environment of the hardened gels. Finally, I will discuss the implications for other hardening gels and for more sustainable construction materials.

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K. Ioannidou, K. J. Krakowiak, M. Bauchy, C. G. Hoover, E. Masoero, S. Yip, F.-J. Ulm, P. Levitz, R. J. M. Pellenq, and E. Del Gado, PNAS 113, 2029 (2016)
A. Goyal, K. Ioannidou, C. Tiede, P. Levitz, R. J-M Pellenq, E. Del Gado, J. Phys. Chem. C 124, 15500 (2020)
A. Goyal, I. Palaia, K. Ioannidou, F.-J. Ulm, H. Van Damme, R. J-M Pellenq, E. Trizac, E. Del Gado, preprint 2020.