Ternary phase diagrams applied to hydrated cement
2015
The phase assemblages that form from the hydration of portland cement
over time, or from changes in composition, can be predicted by thermodynamic modelling (Lothenbach 2010), or simply by mass balance calculations with some knowledge of the relative stability of the hydrate phases.
Thermodynamic modelling can deal with the complexity of cementitious
systems and is well suited to predicting the effect of changes in single or
several components at once as, e.g. discussed by Damidot et al. (2011). To
successfully apply thermodynamic modelling, some knowledge of geochemistry (e.g. which phases can reasonably precipitate or dissolve under the
conditions of equilibrium) as well as practical knowledge of the modellingCONTENTS11.1 Introduction 485
11.2 Ternary diagrams in the CaO-Al2O3-(Fe2O3-MgO-)SiO2-SO3-CO2-H2O system 488
11.3 The CaO-Al2O3-SiO2 and C3A-CaSO4-CaCO3 subternaryphase diagrams 489
11.3.1 The CaO-Al2O3-SiO2 subternary phase diagram 490
11.3.2 The C3A-CaSO4-CaCO3 subternary phase diagram 49111.4 Examples of the application of the CaO-Al2O3-SiO2 and C3ACaSO4-CaCO3 diagrams used in conjunction 492
11.4.1 Portland-pozzolan-limestone cements 492
11.4.2 Comparison with thermodynamic modelling 494
11.4.3 Thaumasite formation 495
11.4.4 Chloride-containing systems 49511.5 Further components 496
11.6 Excel files for plotting subternary diagrams of hydratedportland-pozzolan-limestone cements 498
11.7 Conclusions 500
References 500software being used is needed. For a general overview of the effect of different chemical compositions, ternary phase diagrams provide an effective
means of graphical representation of the thermodynamic predictions. The
present chapter gives an introduction to how these ternary diagrams are
constructed, illustrates their usefulness in predicting the phase assemblage
of hydrated cements and offers access to an interactive excel file for performing this in practice.
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