Re-examination of cement hydration: sol–gel process

Hydration reactions and the resulting nano-structures are responsible for the fundamental properties of Portland cement and concrete. Recent advances in cement hydration and nano-characterisation techniques for Portland cement have started to unravel the basic cement hydration phases (calcium silicate hydrate (C-S-H) gel in particular) at the nano scale. It is likely that Portland cement and several others can be classified as ‘inorganic cements', since they share many common characteristics at the nano-scale structure level; still, each system possesses its own unique reaction mechanisms attributable to specific reaction environments. In this paper, such similarities are discussed and highlighted, when possible, in terms of inorganic polymerisation and sol–gel processes. The ability to tailor chemical structures of Portland cements at the nano-scale level can not only render improved mechanical properties but also possibly create unique microstructures.