Calcium silcate hydrates (C-S-H) is the main solid phase present in hydrated cements. The composition of C-S-H may change depending on the solution in which it is equilibrated. The silica chain length in C-S-H increases with the silicon concentration and the calcium content in the interlayer space with the calcium concentrations. Sodium and potassium are taken up in the interlayer space, preferentially at low calcium concentrations and thus by low Ca/Si C-S-H. Aluminium uptake in C-S-H increases strongly at higher aluminium concentrations in the solution. At low Ca/Si, aluminium substitutes silica in the bridging position, at Ca/Si &gt; 1 aluminium is bound in TAH. Recently developed thermodynamic models are closely related to the structure of C-S-H and tobermorite, and able to model not only the solubility and the chemical composition of the C-S-H, but also to predict the mean silica chain length and the uptake of aluminium.

Calcium silicate hydrates

253rd National Meeting (2017)

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