Coupled effects of silica fume and time after water addition on rheology of fresh concrete

The fresh-state behaviour of plain and silica fume (SF) modified concrete was measured using a wide-gap viscometer, and classical workability (slump flow and J-ring slump flow) was measured. The Herschel–Bulkley (HB) model was used to describe the rheology of fresh concrete and the HB parameters (including yield stress, consistency coefficient, flow index and apparent plastic viscosity) under the coupled effect of SF and time after water addition were derived. According to the experimental results, shear thickening behaviour is found to be strongly influenced by SF content and the time after water addition. In general, the flow index declined with SF and water addition time. A simplified model is constructed to forecast the value of the flow index for the coupled effects of SF content and water addition time.