Effects of limestone powder on shear thinning and shear thickening of cement-fly ash paste

Rheological property of cement pastes with different content (mass fraction of cement) of fly ash and limestone powder was tested by rotation viscometer with type of Rheolab QC. Results show that rheological curves show both shear thinning and shear thickening with the increase of shear rate. Pure cement paste shows shear thinning even in high shear rate. Addition of fly ash and limestone powder not only decreases critical shear stress (τ crit) and critical shear rate (γ crit) of cement paste, resulting in the paste easy to shear thickening, but also decreases rheological index (n), resulting in the increase of shear thinning degree in shear thinning stage, and the decrease of shear thickening degree in shear thickening stage. With the increase of limestone powder content and specific surface area, the rheological index in shear thinning stage increase, resulting in the decrease of shear thinning degree. When limestone powder content increases from 0% to 15%, the rheological index increases significantly in shear thinning stage. ©, 2015, Tongji University. All right reserved.