Large Void Fill

Foamed concrete for Large Void Fills

Foamed Concrete is an Excellent Void fill material, especially for large voids as it is self consolidating and can be pumped to location

A mass infill, or large void, loosely describes a project of sufficient volume where the daily volume is not subject to a maximum material depth. Or, distance required for material to flow. Therefore, the principal task for the foamed concrete is occupy space with a non-structural requirement.

Common Examples of large/ mass void filling

  • Large Tunnels
  • Mines
  • Shafts
  • Addits
  • Sink Holes
  • Dean Holes
  • Subways
  • Road Slabs
  • Bridge spans

For example, large void fills commonly include sinkholes and mines/ caves which undermine existing structures. However, large open areas, requiring a mass infill also feature.

Requirements may include long pump distances. Areas which may be hazardous for overhead works. Danger to humans. Often, no other product is suitable to fill the void. For instance, traditional tipper lorries cannot get close enough because the ground is weak or unstable and prone to collapse. Similarly, large undercuts create features that become difficult to support. Moreover, many large voids, such as, road slabs or trenches include pipes or services that require encapsulation. In short, this will often exclude conventional materials due to their flow characteristics, or their need for compaction, consolidation.

Why Use Foam Concrete for Large Voids?

Foamed concretes are a desirable infill material. Primarily, they are incredibly fluid (high water content with small aggregates). In addition, foam concretes have a high “blow up factor” reducing on-site deliveries. Therefore, pumping further than traditional infill materials is possible. Finally, foam concretes or aerated concretes are self-consolidating. A self-consolidating material does not require compaction or vibration. Making a foamed concrete a safer option where confined spaces or hazardous environments are concerned.

Propump have a long history with large void fills using foam concrete. Notable examples include:

  • Coombe Down Mines – 600,000m³
  • Crossrail temporary works as well as permanent TBM abandonment – 30,000m³
  • Ventilation shafts and decommissioned stations for London underground
  • Pedestrian subway networks in Ipswich and, Maid Marian Way, Nottingham
  • TBM heading material for various major Tunnelling projects.
  • Sinkholes and ground stabilisation in Aylesford, Kent – 3,000m³
  • Light weight Tunnel cap, Gerrards cross, London, 10,000m³

Typical densities range from 500 Kg/m3 to 1400 Kg/m3. Whilst low density mixes such as our 500kg/m³ provide an excellent “blow up”, our 1000kg/m³ “P445” mix provides a good balance of fluidity, strength and robustness when poured into environments that result in pours deeper than 1 metre and will tolerate some water ingress.


Bridges & Roads



Sewers & Tunnels

Large Void Fill

More information

Propump Consultancy Services

Propump news & articles

Why choose foamed concrete?

Projects by Propump

Foamed concrete cube moulds available from stock from ProPump Engineering Ltd

Foamed concrete cube moulds

Large quantities of both 100mm and 150mm foamed concrete cube moulds are kept in stock, available to purchase on a next day delivery.

Please call the office for up to date prices on 01322 429 900 alternatively email