====== Cement ======

[[http://en.wikipedia.org/wiki/Cement|Cements ]] of various types have been in more or less constant use since at least Ancient Roman times. However, the ways in which cements set (via a complex series of chemical hydration reactions) have still not been fully described.

>The hydration of cement is an extremely complex reaction involving chemo-physical phenomena spanning from a nanometer to micrometers in length and from seconds to decades in time."\\ \\ Source : [[http://www.sciencedirect.com/science/article/pii/S0022509616305919|Journal of the Mechanics and Physics of Solids,]] //(paywalled)// Volume 99, February 2017, Pages 211–224

Although several chemical models give a good //approximation// of how a cement will set, they have limitations, particularly in view of the extremely long setting time of some cements which continue to harden over several decades.

>[...] the molecular compositions, structures and changes that occur as a result of hydration are poorly understood, because cement has a composition that is partially crystalline, partially disordered, and holds multiple components that also change with time" \\ \\ Source : [[https://www.scientificamerican.com/article/bp-halliburton-deepwater-cement/| Scientific American]]