Rheology of geopolymer by DOE approach

The effects of solid/liquid content, temperature, curing time and deflocculant concentration on some fundamental rheological parameters of metakaolin-based geopolymer suspensions activated by NaOH were studied by statistical DOE approach. Solid content appears to be the most important parameter among the studied ones. As well known, it has an influence both on viscosity, shear behaviour and yield stress. Instead the additive, an industrial grade sodium polyacrilate, has demonstrated to have a poor effect on the viscosity and yield stress. In synergy with curing time, temperature showed a different effect with respect to its classic rheological influence. In countertrend, increasing the temperature resulted in an increased viscosity due to acceleration of the geopolymerisation reactions.Rheological parameters have proven to be very sensitive to chemical changes in the studied system. In combination with DOE methodology, it is a potent tool for monitoring the microstructural evolution of geopolymers during curing.

► The rheological behaviour of geopolymer suspensions was studied by DOE.
► The study uses a combination of rheology and a statistical methodology.
► Rheological measures permit to study in a very early stage the geopolymerisation.
► The variable temperature acts differently from what is known in literature.
► Temperature increases the viscosity due to the reaction of geopolymerisation.