(BS EN 450-1:2005 - Fineness Category S)

Fly Ash S is an enhanced quality assured fly ash suitable for use in combination with Portland cement (CEM I) in concrete. 


  1. Durability

    Improves concrete durability.
  2. Heat of hydration

    Reduces heat of hydration.
  3. Less risk of ASR

    Minimises the risk of ASR in concrete containing reactive aggregates.
  4. Reduced risk of cracking

    Reduces the risk of early-age thermal cracking in large pours.
  5. Water demand

    Reduced water demand.
  6. Workability

    Improved workability retention.
  7. Reduced bleeding

  8. Pumpability

    Improved pumpability.


  • Wind Farms
  • Infrastructure
  • Major Contracts
  • Nuclear
  • Marine
  • Waste
  • Power
  • Blocks
  • Concrete Block Paving
  • Drainage
  • Grout
  • Soil Stabilisation

Case Studies


Brett Concrete for Crossrail Tunnelling

Crossrail, the new high frequency, high capacity railway, is set to revolutionise travel in London. Construction is due for completion in 2018. And with 26 miles of tunnels, building this new artery passing through 40 stations is one of Europe’s biggest construction projects.

Technical information

Fly Ash S is available in bulk tankers throughout the United Kingdom.  

Tarmac Fly Ash S is a quality assured fly ash conforming to BS EN 450-1 2005: Fineness Category S, with a loss of ignition of less than 7% (LOI Category B). Fineness Category S Ash is a finer ash than Category N Ash.

Tarmac Fly Ash S can be combined with Portland cement (CEM I) in the concrete mixer. Guidance on the appropriate combination for different applications is available in BS 8500: Concrete-Complementary British Standard to BS EN 206-1 and from the Tarmac Technical Helpline.

Tarmac Fly Ash S is a type II addition suitable for use in mixer combinations with Portland cement (CEM I) as defined in BS 8500: Concrete-Complementary British Standard to BS EN 206-1.

The properties of concrete containing Tarmac Fly Ash combined with Portland cement (CEM I) will depend on the proportion of Tarmac Fly Ash. 

Regional Order Numbers:

Scotland & North East England - 0845 4700 300

North & Midlands - 0845 4700 400

South Wales & South West - 0845 4700 500

London & South East - 0845 4700 600

  • Achillies Building Confidence
  • Carbon Trust Standard

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