Steel fibre reinforced concrete

Steel fibre reinforced concrete is one of the harder materials to pump. The base mix needs to be rich enough to support the fibres and the fibres need to be incorporated thoroughly into the mix. If the fibre reinforced concrete is rich and homogeneous; and a modern, well maintained, high pressure concrete pump is used, it will pump without a problem. But if the mix or pump are found wanting, it will inevitably block in the pipeline. Despite these potential problems, steel fibre reinforced concrete was specified for the Bedford Train Care Depot because of its physical properties. It has high flexural strength with good resistance to water ingress and chemical attack.

On planning this contract, Fitzpatrick Contractors Ltd and Hanson Premix determined that the steel fibres were to be added to the base mix on site using a dedicated dosing unit (see photo here). This ensured that the fibres were evenly dispersed throughout the mix. Despite a relatively high dosing rate the concrete was successfully pumped into the formwork for each of the pours. That said, the concrete was monitored at every stage of the process.

The pump chosen for this contract was a Putzmeister M31/5 concrete pump with a maximum theoretical output of 140 cubic metres per hour. This pump was chosen, not so much for its high output but for the boom configuration. The M31/5 boom combines a long reach with a low unfolding height ensuring the concrete can placed in relatively low height buildings with the minimum number so set-up positions.