Abstract
The variation in fresh concrete flow rate over the pipe cross section was investigated on differently coloured
and highly flowable concrete mixes flowing through pipes of different materials (rubber, steel, acryl). First,
uncoloured (gray) concrete was poured through the pipe and the pipe blocked. Similar but coloured (black)
concrete was then poured into the pipe filled with gray concrete, flowing after the gray concrete for a while
before being blocked and hardened. The advance of the colouring along the pipe wall (showing boundary
flow rate) was observed on the moulded concrete surface appearing after removing the pipe from the
hardened concrete. The shapes of the interfaces between uncoloured and coloured concrete (showing
variation of flow rate over the pipe cross section) were observed on sawn surfaces of concrete half cylinders
cut along the length axes of the concrete-filled pipe. Flow profiles over the pipe cross section were clearly
seen with maximum flow rates near the centre of the pipe and low flow rate at the pipe wall (typically
rubber pipe with reference concrete without silica fume and/or stabilizers). More plug-shaped profiles, with
long slip layers and less variation of flow rate over the cross section, were also seen (typically in smooth
acrylic pipes). Flow rate, amount of concrete sticking to the wall after flow and SEM-images of pipe surface
roughness were observed, illustrating the problem of testing full scale pumping.
© 2009 Elsevier Ltd. All rights reserved.
and highly flowable concrete mixes flowing through pipes of different materials (rubber, steel, acryl). First,
uncoloured (gray) concrete was poured through the pipe and the pipe blocked. Similar but coloured (black)
concrete was then poured into the pipe filled with gray concrete, flowing after the gray concrete for a while
before being blocked and hardened. The advance of the colouring along the pipe wall (showing boundary
flow rate) was observed on the moulded concrete surface appearing after removing the pipe from the
hardened concrete. The shapes of the interfaces between uncoloured and coloured concrete (showing
variation of flow rate over the pipe cross section) were observed on sawn surfaces of concrete half cylinders
cut along the length axes of the concrete-filled pipe. Flow profiles over the pipe cross section were clearly
seen with maximum flow rates near the centre of the pipe and low flow rate at the pipe wall (typically
rubber pipe with reference concrete without silica fume and/or stabilizers). More plug-shaped profiles, with
long slip layers and less variation of flow rate over the cross section, were also seen (typically in smooth
acrylic pipes). Flow rate, amount of concrete sticking to the wall after flow and SEM-images of pipe surface
roughness were observed, illustrating the problem of testing full scale pumping.
© 2009 Elsevier Ltd. All rights reserved.
