Ashford Crescent Flood Alleviation Scheme

Ashford Crescent Flood Alleviation Scheme

Project brief

Balfour Beatty Utilities were appointed to construct a series of surface water drainage ducts and a collection tank. The collection tank was a 20m diameter, 14m deep vertical shaft constructed from precast concrete segments. Once in place the concrete segments are surrounded by grout, this fills and seals any voids. The amount of grout required varies with ground in which the segments are being placed.

The solution

Grout is typically supplied in 25kg paper bags which are ripped and tipped into a mixer above ground, the flowing grout is then pumped to the required location. Balfour Beatty recognised that they could improve their site operation by the use of a Tarmac silo.

The silo supplied was one that has been extensively developed and supported by Tarmac’s mortar business. The requirements for each silo is a level 3x3x0.125m C35 reinforced concrete base, a single phase type C or D power supply and a mains water connection via a 25mm diameter pipe or equivalent. Training with regard to operation, cleaning, safety and maintenance was delivered from a Dry Silo expert as part of the installation.

The benefits

  • The dry grout is stored in a silo which offers greater protection on a construction site and takes a smaller footprint than palletised 25kg bags.
  • The silo is delivered with a purpose designed mixer (no extra mixer hire necessary).
  • Push button control of the supply of grout – simply starting and stopping the mixer.
  • The consistency of the mix can be varied almost instantaneously at the silo by turning a tap controlling the water supply.
  • The manual handling task of ripping and tipping bags is removed – reducing both the health and safety risk and the labour requirement.
  • The mixing operation of dry powders takes place at the factory under controlled conditions and prior to water addition in the silo mixer which is effectively sealed, both aspects of the system reduce the risk of dust emission to the environment.

Site waste is reduced via:

  • No requirement to dispose of packaging/pallets.
  • Touch button control on the continuous mixer means that the precise amount of grout required is mixed.
  • Silo is delivered with product ready for production.
  • Further bulk deliveries are made to site using a conventional powder tanker, capable of delivering 26 tonnes. The unloading is via compressed air transfer and does not require a lifting operation on site.


  • Client: United Utilities
  • Project: Ashford Crescent Flood Alleviation Scheme, Preston
  • Contractor: Balfour Beatty Utilities/Tunnelling
  • Product: GM3 supplied in a Tarmac Mortar silo with M-Tec D50 mixer