Opti WCR

OPTI-WCR - OPTIMISATION OF THE WATER-TO-CEMENT-RATIO TO IMPROVE THE
SETTING, DRYING AND HIGH TEMPERATURE BEHAVIOUR OF REFRACTORY CASTABLES:

The general purpose of this project is to attain a deeper understanding
of the interaction properties of cement lime (CAC) with other aggregates
in the formulation. This knowledge is indispensable to understand or
predict the performance of refractory castables. This topic is already a
priority field of investigation as long as hydraulic bond systems are in
use. However most research work published in literature put focus on
details (e.g. solely the temperature dependence of the setting velocity,
the setting velocity strength evolution as a function of time etc.).
Very often the basic conditions how the tests were performed are not
commented. Therefore the objective of this project is to control all
known influences that affect the setting behaviour, the strength
evolution, the drying behaviour and the high temperature performance.
Beside the typical parameters temperature, relative humidity,
workability (viscosity, compactibility), and CAC- microfines-additive
combinations a key issue of this project is how the water-to-cement
ratio (wcr) affects the strength evolution and in consequence the
material performance at service conditions. To date the influence of wcr
for CAC containing refractory castables was only evaluated as an issue
for the adjustment of consistency of castables but not systematically in
connections with their high temperature properties. Therefore wcr is a
key value for calcium silicate products from the civil engineering
industry but the influence was neglected for CAC containing refractory
castables. This is because the CAC in refractory castables loses its
functionality after the first heat-up and therefore is always seen as a
temporary binder. The importance for the high temperature performance
was always neglected or even worse in that case that it is often accused
to reduce the refractoriness of the product.
It is expected that the proper adjustment of the wcr will significantly
enhance the performance of refractory castable. It will be possible to
determine the precise cement concentration for any ambient condition.
During the project it will be carefully evaluated how the adjusted
cement concentration affects the setting, hardening, drying and high
temperature properties. For a proper material development it is
indispensable to investigate every step of the whole lifecycle.