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.
Correlation between hydration mechanism and ultrasonic measurements in an aluminous cement: effect of setting time and temperature on the early hydration
Abstract Early hydration (0–24 h) of Secar 71, a calcium aluminate cement, has been examined in-situ by ultrasonic testing for pastes prepared at 20 °C (W/C=0.33, 0.38 or 0.40) and at 5 °C, 40 °C and 60 °C (W/C=0.33). The ultrasonic measurements consist of following the velocity of the longitudinal ultrasonic wave, V L (frequency=1 MHz), transmitted inside the specimen and also the reflection coefficient, R , at the interface between the cement and the container of the paste, which is a polymethylmethacrylate mould. The variations of V L as a function of setting time can be described by a dissolution-precipitation mechanism. Lastly, the changes in R can be linked with morphological changes occurring inside the cement paste, especially the progressive formation of crystallised hydrates.
Ultrasonic propagation through hydrating cements
Abstract Hydraulic cements develop mechanical strength and low permeability as a result of hydration, which involves chemical reactions between water and the anhydrous compounds present in the cement. Solid hydration products form both at the surfaces of the cement particles and in the pore space by nucleation and aggregation. As a result, the solid phase becomes highly connected and the material transforms from a viscous suspension of irregularly-shaped cement particles into a porous elastic solid with non-vanishing bulk and shear moduli. This transition to an interconnected solid phase is an example of a percolation transition. In this paper, measurements of the velocity of ultrasonic longitudinal and shear waves in ordinary Portland cement undergoing hydration are reported. The cement slurries were prepared in accordance with the American petroleum Institute (API) specification for class G oil-well cement with various additives. After the time at which the cement becomes interconnected, the effective bulk and shear moduli are found to be linearly related and the effective Poisson's ratio is observed to decrease from the value of 0.5, characteristic of a fluid, to values characteristic of a porous elastic solid.