case study: London Bridge Station Arch Infilling 
GS Foam Concrete have been working at London Bridge station for Costain Ltd for over 3 years to infill various voids throughout Network Rail’s station redevelopment. 
Costain instructed GS Foam to infill a large number of redundant brick arches which would then be excavated during other works. These arches were across the whole length of the live lines so each arch was infilled as the redevelopment progressed. 
To reduce the lateral pressures on the arches the foam concrete had to be lightweight and to achieve a compressive strength of 2.5n/mm2. The foam concrete was used to strengthen the arches while other works in the vicinity went ahead. 
The mix used was a P725 @ 800kgs wet density, this was cement only foam concrete. 
The foam concrete was produced on site on Stainer street which was directly below the arches and then pumped using ground lines via the static concrete pump to the platform level and then into the core holes in each arch. 
Due to the lightweight properties of the foamed material the volume per lift did not exceed 1m and in some areas only a height of 500mm was allowed. 
Once the foam concrete has achieved the correct strength the areas around the arches were excavated to allow further works to progress. 
The foam concrete was placed via GS Foam’s own concrete pump and a static pump; both using horizontal and vertical pipelines to reach each arch. 
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