Technical challenges overcome for hospital contract

Hanson’s technical team overcame a range of issues to supply 17,000 cubic metres of highly specialised concrete to The Christie hospital in Manchester where the UK’s first cancer proton beam therapy centre is being constructed.

The bulk of the material was placed in the basement bunker of the three storey building, which will house a state-of-the-art nuclear reactor where protons and neutrons are separated ready for use in three treatment rooms above.

Concrete technical services manager Terry Balmer said producing the mix was a real challenge. “We had a really onerous oven dry density requirement to meet; the concrete had a maximum water to cement ratio of 0:40, with a maximum cement content of 355kg per cubic metre.That meant we could only add 138 litres of water for each cubic metre to produce concrete that had to be virtually self-compacting and placed by pump in continuous pours of up to 400 cubic metres in elements up to two metres thick.”

The mix contained 70 per cent Regen so the setting time was relatively slow and holding the material in suspension over two metre depths for long time periods was also problematic.

“Due to thermal issues we had to use limestone aggregate, which isn’t as effective in achieving higher density requirements,” said Terry.

“In short, almost all the required technical properties of the concrete were at odds with each other and at odds with the engineering design of the interlocking concrete elements!”

Every delivery was tested for fresh wet density and consistence prior to placement. “It was one of the most technically challenging jobs we have ever done,” said Terry.