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Determination of the Foam index of a Coal Fly Ash and Portland Cement Slurry[edit]


  • Safety glasses must be worn in the lab at all times.
  • Full-length pants are required in the lab.
  • Close-toed shoes are required in the lab.
  • Consult MSDS of the AEAs being evaluated for AEA-specific safety considerations.


Stable foam: A continuous foam layer that covers the entire surface of the liquid.


  • Pipette capable of delivering a drop volume of 0.02ml per drop
  • 250ml wide-mouth LDPE screw top container
  • Wrist-action laboratory shaker


  • Coal fly ash sample
  • Portland cement sample
  • Distilled water
  • Air entraining admixture standards:
    • Any known concentrations may be used. Suggested concentrations are 2%, 6%, 10% and 15%.
    • Mix one liter batches.
    • Take note of the manufacturer's recommendations regarding shelf life of mixed solutions.

General Foam Index Procedure[edit]

  • 10g of solid (portland cement or portland cement and fly ash)
  • 25ml distilled water
  • AEA standard solution added in approximately 20 microliter aliquots
  • Test must be completed in 12-18 minutes
  1. In a 250ml, wide-mouth, screw-top LDPE container, add 25ml distilled water and 10g solids.
  2. Secure container in a wrist-action shaker and agitate 30s at a stroke length of 20cm.
  3. Leave the container in the shaker, remove the cap and add one aliquot AEA standard solution.
  4. Reseal the container and agitate for 10 seconds at the same stroke length.
  5. While still secured in the shaker, open the container and observe if a stable foam is present. If not, repeat previous two steps until a stable foam develops, recording the number and volume of aliquots.
  6. The foam index is the sum of the standard solution aliquot volumes.
  7. The specific foam index is the AEA portion of the foam index.
  8. The relative foam index is the ratio of fly ash specific foam to cement specific foam index expressed as a percentage.

Overall Procedure[edit]

The overall procedure consists of:

  1. Perform the general foam index test with a 10g sample of cement only
  2. Calculate the foam index and specific foam index for the cement only.
  3. Perform the general foam index test with 8g cement and 2g fly ash.
  4. Calculate the foam index and specific foam index for the cement-fly ash mixture.
  5. Calculate relative foam index.