Cornish Mainline, St Austell

Beneath the main line at this location was a disused mineshaft that had historically been backfilled but there was there was a danger of collapse. To remove this risk precast units each 5.5m long and 1.6m wide were to be used to bridge over any potential collapse.

A total length of 20m was required to be bridged so a total of 6 units were required under each rail track and in order for them to behave monolithically they needed to be “stitched” together using ready-mixed concrete.

Our Concrete business proposed the use of  Diamondcrete RA concrete with indicative insitu strength of 5N/mm2 at seven hours and indicative insitu strength of 10N/mm2 at eight hours.

The strength gain of concrete at an early age is extremely temperature dependant. Concrete’s bespoke Diamondcrete RA concrete is designed to both optimize the increase in temperature and the rate of increase in temperature of the insitu concrete.

Prior to supply we also proposed a site trial was carried out to enable replication of ambient placing conditions and the dimensions of the element being cast, including the use of insulation on the cast area to help maintain the heat of hydration and therefore maximise the rate of strength gain.