Site report: Pumping concrete into the bottom of a shutter

Mowlem Building had to construct seventeen reinforced concrete columns in the basement of a partially built office block in Newcastle-under-Lyme. The columns were to be formed from the sheet piling faced with permanent steel shutters and had to extend from the basement floor to the ring beam.

The original plan was to pump concrete into the columns through a letterbox near the top of the shutter. However, this solution was fraught with practical difficulties; how to get the concrete to the top of the shutter, how to prevent segregation, how to compact the concrete, and how to fill in immediately below the ring beam. Camfaud suggested pumping from the bottom of the formwork through pipes welded to the shutter. We provided seventeen stub pipes which were then welded over the injection points. A shut-off valve was then coupled to each stub pipe.

On the day of the pour, Camfaud supplied an M24 mobile concrete pump complete with an operator experienced in this pumping technique. The concrete placing boom was threaded through the steel frame buildings and down into the basement. Approximately 40 meters of pipeline were connected from the end of the boom to the first shut-off valve. The concrete was pumped steadily into the first shutter with the level of concrete being monitored. The pump was slowed as the shutter filled and was stopped as soon as the concrete grout seeped from the top of the shutter. Once the shutter was filled, the gate valve was closed, the delivery hose disconnected and the line coupled up the next shutter.

This process was repeated a further seven times. At the end of the day, the pipeline was stripped down and cleaned out. The following day the pump returned, the shut-off valves were removed, cleaned and coupled to the next batch of shutters and the pumping process re-commenced with the final nine shutters being filled. At the end of the second day, the pipeline was stripped down cleaned and stored back on the pump. The shut-off valves were stripped and cleaned the following day. After two days of work, all seventeen columns had been concreted from floor to ring beam above with no problem from concrete segregation or voiding.

• Pump: M24

• Customer: Mowlem Building

• Site: Newcastle under Lyme

• Concrete Supplier: Tarmac Topmix

• Date: December 2004