Flow of SCC along surfaces

The flow conditions near solid surfaces (no-slip, slip, lubrication) were investigated using the results of gravimetric flow tests, full scale instrumented pump tests and rheological measurements on matrix, mortar and self compacting concrete. Modelling with the measured data could fit plug-flow with a 0.6 - 1 mm thick lubrication layer of matrix having similar lubrication layer viscosity as the lower values of Kaplan: 175 – 320 Pa.s/m. Visualization of boundary flow conditions and flow profiles and measurements of concrete sticking to different pipe materials related to increased flow rate along smooth acryl and reduced along rougher rubber surfaces. The existence of plug flow during SCC pumping may be questioned and possible causes for formation of a lubricating layer and a plug are discussed as well as a brief review of void formation at the surface.