A study of the rheological properties of polymer modified cement pastes
The work outlined in this thesis describes how rheological techniques can be used to gain insight into the behaviour of complex hydrating systems. These techniques are currently used to elucidate interparticle interactions of concentrated colloidal dispersions. Those used here were stress relaxation, pulse shearometry and oscillation. These enabled parameters such as the dynamic moduli, relaxation moduli, relaxation spectrum and limiting moduli to be obtained. These all give a measure of the strength of interaction of the colloidal system under different conditions, without reducing these interactions by inducing flow. Calorimetric data was obtained for a hydrating cement paste. The particle and floc size of this cement was also measured. The data were found to be in accord with one another, and with current theories of the hydration processes of cement. In combination with the rheological parameters measured this enabled the extent and strength of attraction between the particles of a cement paste to be determined, as a function of the age of the paste. The adsorption characteristics of surfactant on cement were measured, as was the effect of surfactant on the particle and floc size of hydrating cement. Coupled with a measure of the rheological parameters of the cement-surfactant system, an understanding of the effect of surfactant on a hydrating cement paste was obtained. Similarly the effect of the addition of styrene-butadiene polymer latex particles, with and without excess added surfactant, was able to be determined. This information was obtained for hydrating cement pastes, both in the presence and absence of added polymer, at both ambient and non-ambient temperatures.