Скачать или смотреть The Materials Science of Sustainable Cement

NCI-SW/¡MIRA! Colloquium 4 November 2021.

Dr. Claire White is an associate professor of civil and environmental engineering at Princeton University.

Abstract: With the world facing a climate crisis due to increasing CO2 emissions, there is pressing need to develop and implement sustainable construction/engineering materials across the globe. Alkali-activated materials (AAMs) are one such sustainable alternative to conventional Portland cement concrete; yet questions remain regarding the long-term behavior of AAMs. Furthermore, for Portland cement, the use of extensive clinker substitution to reduce CO2 emissions has led to changes to the underlying chemistry of the main binder gel (calcium-silicate-hydrate, C-S-H, gel), where it is uncertain how these novel supplementary cementitious materials augment the long-term behavior (e.g., gel stability and pore structure) of the cement binder. In this talk, I will outline how fundamental materials science research is being used to address the long-term behavior unknowns of AAMs and certain Portland cement-based systems, where we are linking key experimental techniques with atomistic and larger length scale simulations. In particular, to assess gel stability in calcium-rich AAMs, we have used density functional theory (DFT), synchrotron-based X-ray pair distribution function (PDF) analysis and nuclear magnetic resonance (NMR) to investigate the influence of alkali and alumina incorporation on the structure and thermodynamics of C-S-H gel. The DFT results point toward a clear upper limit for sodium incorporation, beyond which the stability of the phase is compromised, while the experimental results show how alumina can be utilized to combat the destabilizing effects of sodium. We have also used DFT to uncover the early stage formation behavior of C-S-H gel and the influence of sodium and alumina, which has led to a tentatively proposed formation mechanism of the gel.