Effect of maximum packing fraction of powders on the rheology of metakaolin-based geopolymer pastes

In this work, we study the effect of maximum packing fraction of powders on the rheology of geopolymer pastes. A large range of metakaolin powders is generated either by blending or grinding powders. Blends of metakaolin with quartz and limestone are also studied. We show that the compressive packing model is able to predict correctly over a wide range of values the maximum packing fraction of these powders. We show that an increase of the maximum packing of powders leads to a decrease of the viscosity of geopolymer suspension at a constant solid volume fraction. We finally show that the viscosity of studied geopolymer suspensions can be well predicted by the Krieger Dougherty relation. We suggest that the highest potential degree of freedom allowing for the control of the viscosity of geopolymer pastes without modifying the composition of the suspension lies in the maximum packing fraction of the solid powders.