Fly Ash Bound Material (FABM) Footways

  • Client:  Amey and Hampshire CC
  • Site: Various – Hampshire
  • Works Type:  HBM Manufacture
  • Material:  FABM – Fly Ash Bound Material
  • Specification: TRL611/BS EN 14227

As part of the joint collaborative venture between Hampshire County Council, Amey and Allasso Recycling, a need for a material with an extended shelf life was identified to enable the use of HBM in small works. Allasso Recycling developed a FABM 2 material that is capable of storage for up to 8 weeks depending on storage and weather conditions.

The product is a slow hydraulic material with an additive which coats the incorporated lime, inhibiting reaction until compaction.

FABM Stockpile

FABM incorporates PFA (Pulverised Fuel Ash) with lime. The material utilises pozzolanic reaction as cement replacement. The pozzolanic reaction converts a silica-rich precursor with no cementing properties, to a calcium silicate, with good cementing properties. ‘Slow Hydraulic’ materials have a protracted strength gain when compared to quick hydraulic materials. This can have the advantage of

  • Increased handling times
  • Stockpiling options
  • Reduced risk of reflective cracking
  • Consists of up to 97% recycled/secondary materials
  • The ability to incorporate asphalt waste containing coal tar

FABM is produced to national specification BS EN 14227, under a quality system conforming to UKAS accredited ISO 9001 and is monitored through regular testing under a quality management plan.

The materials rely on the mechanical interlock of the aggregate initially until hydraulic strength takes effect. The material can be produced ad-hoc on a mobile contracting basis through our mobile plant capable of up to 400 tonnes per hour production.

HBM Carriageway
The material is used on footways, vehicular crossings and carriageways throughout the county as a sub base, base and binder course replacement material, allowing reduced construction depth when compared to traditional unbound sub base, asphalt base and binder solutions. The material offers maintenance teams and subcontractors unprecedented flexibility with the ability to store the material on site, quicker construction due to single lift working with the added benefit of zero wastage as is often found with hot bituminous materials.

The material is part of the solution that won the 2015 Highways Maintenance Excellence Awards and has been used on hundreds of sites in the county with thousands of tonnes now laid. The FABM solution is part of the overall recycling strategy employed within Hampshire and saves the county council in excess of £1m per annum. Feedback for the material from client, contractor and subcontractor has been positive with enthusiasm for the flexibility sit affords.

Key Benefits

  • Enhanced quality by means of ex situ processing as each load of incoming material can be inspected for quality.
  • Sustainable Construction Material
  • Sustainable use of Coal Tar Bound Materials
  • Increased Performance
  • Increased operational flexibility, efficiency and effectiveness
  • Significantly reduced costs