Ultrasonic sound speed of hydrating calcium sulphate hemihydrate; part 2, the correlation of sound velocity to hydration degree
In this article the sound velocity through a mix is correlated to the hydration degree of 
the mix. Models are presented predicting the sound velocity through fresh slurries and 
hardened products. These two states correspond to the starting and finishing point of the 
hydration process. The present research shows that a linear relation between the amount 
of hydration-product (gypsum) formed (Smith et al., 2002) and sound velocity can be 
used to describe this process. To this end, the amount of hydration-product formed is 
determined by the using the equations of Schiller (1974) for the hydration process and 
of Brouwers (2010) for the volume fractions of binder, water and hydration products 
during the hydration process. The presented model shows that the induction time and 
gypsum growth rate are linear related to the water/gypsum-ratio.
The course of hydration: Its practical importance and theoretical interpretation
The practical usefulness of plaster is due to the solidification (set) which accompanies the chemical process of hydration. The paper exposes the mathematical relationship between the time it takes to hydrate (completely or to any incomplete extent) and such physicochemical parameters as the rates of dissolution and growth of the hemi- and dihydrates respectively, the solubilities, the number of dissolution and growth nuclei, particle shapes, etc. Possible modes of action of impurities, retarders and accelerators are suggested by implication. The basic principles from which this relationship is derived are mentioned. The various very different shapes which the hydration curve (extent of conversion versus time) can take are shown. A simple method is indicated to express mathematically the hydration curve of any given plaster. Reference is also being made to the relation between set and water gauge. Finally, the limitations of the theory are indicated.
Contribution to the study of the kinetic mechanism of aluminous cement setting II - Release of the factor resposible for breaking the latent period by the dissolution of a fraction of the initial cement
Abstract The comparison of Wells (W) and filtrate development (B) curves, published in the first article (1) led us to conclude that there is no heterogeneous nucleation during the latent period either for the aluminous cement (Fondu) or for pure monocalcium aluminate (CA). This new study aims to supply new experimental data showing clearly that the factor responsible for instant hydrate precipitation, i.e. for breaking the latent period, is related too the dissolution of a fraction of initial cement, this factor being liberated by such dissolution.