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.
Net Spaces in Categorical Topology a
In the paper we introduce the notion of S‐nets, S a nonempty construct, as a generalization of the usual nets. S‐net spaces and continuous maps between them are then defined in a natural way. For S‐net spaces we introduce a number of axioms and study the categories obtained. We find some topological and Cartesian closed categories of S‐net spaces and describe their relations to certain known topological categories.