Influence of Nano-SiO(2), Nano-CaCO(3) and Nano-Al(2)O(3) on Rheological Properties of Cement–Fly Ash Paste

Rheological curves of cement–fly ash (C–FA) paste incorporating nanomaterials including nano-SiO(2) (NS), nano-CaCO(3) (NC) and nano-Al(2)O(3) (NA) at different resting times (hydration time of 5 min, 60 min, and 120 min) were tested with a rheometer. The rheological behaviors were described by the Herschel–Bulkley (H–B) model, and the influences of these nanomaterials on rheological properties of C–FA paste were compared. Results show that the types, content of nanomaterials and resting time have great influences on the rheological properties of C–FA paste. Incorporating NS and NA increases yield stress and plastic viscosity, and decreases the rheological index of C–FA paste. When the content of NS and NA were 2 wt%, the rheological index of C–FA paste was less than 1, indicating rheological behavior changes from shear thickening to shear thinning. Meanwhile, with rising resting time, yield stress and plastic viscosity increased significantly, but the rheological index decreased evidently, showing paste takes on shear thinning due to the rise of resting time. However, incorporating 3 wt% NC and the rising of resting time did not change the rheological properties of C–FA paste. These differences are mainly that the specific surface area (SSA) of NS (150 m(2)/g) and NA (120 m(2)/g) are much larger than that of NC (40 m(2)/g). The huge SSA of NS and NA consume lots of free water and these tiny particles accelerate the hydration process during resting time.