Who on Earth would not like a concrete subject? The Concrete Sustainability Hub (CSH) at MIT studies fundamentals to improve on concrete use. CSH also stands for calcium silicate hydrate, the binder phase of concrete. The Great Dome at MIT, shown below in an architectural draft, contains a "cement liner" on sandstone overlay. This image shows, at the top right corner, the CSH model that was proposed by A realistic molecular model of cement hydrates in Proceedings of the National Academy of Sciences on September 22. Submitted by Roland Pellenq et al. the paper is free online through the PNAS open access option.
Basically, a group of MIT researchers used computational techniques to determine the three-dimensional structure of CSH. Their perspective includes: (1) crystalline minerals tobermorite [Ca5Si6O16(OH)2.7H20] and jennite [Ca9(Si6O18)(OH)6.8H2O] are not strict structural analogs; (2) the chemical composition of CSH is the most essential property in formulating a realistic molecular description. In fact, they propose (CaO)1.65(SiO2)(H2O)1.75 ; (3) once the carbon to silicon (C/S=1.7) ratio is described correctly, a number of structural features and physical properties are obtained in atomistic simulations.
Crystal structure of jennite. (Credit: Wikipedia)
The authors mention that a separate publication will present the thermodynamic and dynamic properties of CSH and the state of water in the model: "A file containing all of the atomic coordinates is available upon request to RJM Pellenq (firstname.lastname@example.org
) or FJ Ulm (email@example.com
The Great Dome at MIT, showing the proposed CSH structure in the top right corner. (Image created by KJ Van Vliet; architectural drawing supplied by M. Parkin; CSH generated by R. Shahsavari.)