Hydration Modeling of Calcium Sulphates

The CEMHYD3D model has been extended at the University of Twente in the last ten years [1,2]. At present the cement hydration model is extended for the use of gypsum. Although gypsum was present in the model already, the model was not suitable for high contents of gypsum and did not include the transitions between the different calcium sulphate phases (anhydrite, hemihydrate and gypsum). Besides that gypsum was seen as intermediate phase instead of a final phase. The presented model addresses these problems and has the possibility to simulate the microstructure development of gypsum, including reaction kinetics (dissolution, diffusion and precipitation) and the formation of gypsum needles. The model enables multi-time modelling which means the possibility to zoom in and out on the hydration process with respect to time. Multi-time modelling enables the user to study the hydration in more detail in both the early phase (hours) and on the long term (years). This modelling is needed, since the hydration of calcium sulphates is very short compared to that of cement.