case study: St Ann's Subway, Rotherham
GS Foam Concrete were awarded a contract to infill a redundant subway as part of a highways improvement scheme in Rotherham.
The subway was infilled over 3 days with complete client satisfaction.
The mix design used on this project was P370 @ 1500kgs wet density to achieve a compressive strength of 4n/mm2 @ 28 days. The subway was 18m long, 2.4m high and 2.5m wide. The volume for this infill was 108m3.
The GS Foam site team installed 2 sacrificial hoses to the subway soffit, one hose at 15m and a shorter hose at 3m. Also installed in each corner of the subway was a 76mm hose to act as a vent pipe. All the hoses were installed prior to the shutter/formwork being erected.
Each hose was sealed into the shutter with enough hose left showing so we could clamp our delivery hose off the concrete pump and place the foamed material through this pipeline.
Due to the nature of the foam concrete a maximum pour height of 1m is the most we can place in one visit otherwise the foamed material starts to crush under its own weight adding volume to the original order, this is due to the wetter material crushing down the dryer material.
Most subways require sacrificial hoses to be installed; this is so the foamed material is uniform across the whole length and level throughout. By installing sacrificial hoses, the foam concrete can be placed via the different hose lengths which in turn will take the pressure off any formwork/shutter as material is spread out rather than all the material being placed from one end only.