Influence of deflocculants on the cement hydrate phase formation and technological properties of CAC-bonded castables during the first heating process

Abstract

The mechanism of growth and decomposition of calcium aluminate cement hydrate phases (CAH phases), which determine the drying behaviour of calcium aluminate bonded castables are not well understood. This paper focuses on the influence of different deflocculants (polyphosphate, acrylate, polycarboxylate ether) on the formation of hydrate phases and their effect on the technological properties of medium cement castables during the initial heating. To improve the understanding on the CAH phase formation and decomposition, the investigation of the technical properties (flexural strength and open porosity) of the castables at different temperatures during first heating was combined with SEM, XRD phase analysis and pore size analysis. Flexural strength was found to develop differently with increasing temperature depending on the type of dispersing agent in use. A significant influence of the deflocculants on the pore size distributions was found. SEM images show the differences in shape and size of hydration products.

Keywords

• Refractory castable
• Cement hydrate phase
• Thermal decomposition
• Deflocculant