Construction of one of the world's largest underground laboratories at the CERN centre for nuclear research in Geneva has hit a milestone with completion of a massive 5m thick, 85m long and 30m wide reinforced concrete floor slab. The slab forms the base of a giant 34m high cavern, 100m below ground. It will house highly sensitive monitoring equipment as part of a US$11bn upgrade of CERN's 26.7km long particle accelerator. Super-cooled magnets operating at close to absolute zero (-273infinityC) will input 100 times more energy to particles orbiting in the accelerator. Measuring these high-energy collisions requires a detector weighing 8,000t and standing as tall as a five storey office block. A Schwing BPL900 truck mounted concrete pump poured 8,000m 3of concrete into the slab. The concrete was delivered from the surface via a 150mm diameter steel delivery pipe, with the truck used only for its distribution arm. Lead consultant is Scott Wilson Piesold in joint venture with ElectricitÚ de France.