Rheology of self-compacting concrete containing silica fume and recycled aggregates

Rheology of Self-Compacting Concrete (SCC) containing selected silica fume dosages (0% (control mix), 5%, 10% and 15%) in a binary binder has been investigated using the flow-curve test protocol implemented on a co-axial cylinder rheometer. At each silica fume dosage, coarse recycled concrete aggregate volumetric replacement levels were 0%, 50% and 100%. Calibration of selected flow models with the measured flow data showed that rheology transitioned from shear thickening to shear thinning as the silica fume dosage increased from 0% to 15%, other mix constituents remaining unchanged. Similar flow behaviour was noted in the SCCs made with the recycled concrete aggregates (SCRACs) across all replacement levels though for a given silica fume dosage, degree of shear thinning decreased with increasing contents of the coarse recycled aggregates. The experimental results have been used to propose a workability box containing bounds for acceptable rheology of the SCCs and the SCRACs.