Sodium--alumina and related phases

Kummer, Prog. Solid State Chem. 7, 141-75 (1972). J. H. Kennedy, Topics in Applied Physics 21, 105-41 (1977). 

The important compounds in Portland cement are dicalcium silicate (Ca2Si04) 26%, tricalcium silicate (CasSiOs) 51%. tricalcium aluminate (Ca3Al206) 11% and the tetracalclum species CaaAbFe Oio (1%). The principal constituent of moistened cement paste is a tobermorite gel which can be represented schematically by the following idealized equations  

The adhesion of the tobermorite particles to each other and to the embedded aggregates is responsible for the strength of the cement which is due, ultimately, to the formation of -Si-O-Si-0 bonds. 

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