Rheological characterisation of cement pastes with nanosilica, silica fume and superplasticiser additions

This paper reports the effect of silica fume (SF), nanosilica (NS) and superplasticiser (SP) addition on the rheological behaviour of Portland cement pastes with different amounts of SF (0-10%), NS (1%) and SP (0-0.4%) and water to binder (W/B) ratio of 0.4. A rheometer with concentric cylinders geometry was used and the maximum shear rate of 100 s(-1) was applied. SP decreased the hysteresis area, while SF and NS increased it. Samples with NS showed high slopes in descending curves, while samples with SF and high dosages of SP showed lower values. In both cases, the Bingham model resulted in negative values for the yield stress, so that the Herschel Bulkley model was used instead. The spread values variation on flow table did not follow a linear regression model. For this investigation, commercially available SF and NS were used.