Towards an optimization of the formulation of geopolymers in the fresh state: Rheological approach

In this work, we are interested in describing the evolution of the rheological behavior of geopolymer materials since their elaboration until the start of their kinetics of setting. We considered the case where these materials are obtained from the dissolution of a quantity S of metakaolin in a quantity L of alkaline activation solution (sodium-based). In this context and for all the values of the structural identification parameters P = (% Na2O) and R-3 = (L/S) in our experiments, it has been established that the rheological behavior is described by the viscoplastic Herschel-Bulkley model. In particular, we have been able to determine how rheological parameters of the model are affected by variations of P and / or R-3. For the considered formulations, this analysis is of importance insofar as it was at the base of the identification of critical values of P and R-3. Moreover, we verified that for these values, the setting time is maximum. This result is retained to define the optimized formulation of our materials.