Rheological behaviour of different grades of self-compacting concrete containing recycled aggregates

Rheological behaviour of three grades of Self-Compacting Concrete (SCC) containing selected volumetric replacement levels of coarse recycled concrete aggregates (SCRCA) is reported. The binder in the control SCC was cement. Fly ash and silica fume were added to the control mix in binary and ternary blends to achieve the normal-, the medium- and the high-strength SCRCAs. Like the SCC made with the natural aggregates, the normal-strength SCRCA showed a shear thickening response. Its flow behaviour could be described using the Modified Bingham (MB) as well as the Herschel-Bulkley (HB) model. Although rheology of the medium- and the high-strength SCRCAs could be represented by the Bingham model, a more detailed analysis of their flow data using the MB and the HB model indicated shear thinning behaviour. This response is attributed to the presence of silica fume in these two concrete grades. The results of this investigation have implications for formwork pressure, multi-lift casting, pumping and segregation resistance of SCRCA.