Rheological Evolution of Alkali-Activated Low-Grade Metakaolin Pastes

This study compares the rheological development of low-grade metakaolin clays mined from different geographical locations in the US. Small amplitude oscillatory shear (SAOS) is used to monitor the structural build-up of these alkali-activated pastes. Time sweeps of the storage modulus, loss modulus and the phase angle are used to understand their viscoelastic properties and determine their initial setting times. These results are validated with the ASTM Vicat needle test. Isothermal calorimetry is performed to link the rheological development of this cementitious system with its degree of hydration. The results indicate that the SAOS can prove to be a valuable testing method to characterize emerging low-carbon binders by offering a material-efficient, low-error alternative to traditional setting time tests while providing additional insights into their structural evolution.