Determination of the Foam index of a Coal Fly Ash and Portland Cement Slurry
- 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
- 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
- In a 250ml, wide-mouth, screw-top LDPE container, add 25ml distilled water and 10g solids.
- Secure container in a wrist-action shaker and agitate 30s at a stroke length of 20cm.
- Leave the container in the shaker, remove the cap and add one aliquot AEA standard solution.
- Reseal the container and agitate for 10 seconds at the same stroke length.
- 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.
- The foam index is the sum of the standard solution aliquot volumes.
- The specific foam index is the AEA portion of the foam index.
- The relative foam index is the ratio of fly ash specific foam to cement specific foam index expressed as a percentage.
The overall procedure consists of:
- Perform the general foam index test with a 10g sample of cement only
- Calculate the foam index and specific foam index for the cement only.
- Perform the general foam index test with 8g cement and 2g fly ash.
- Calculate the foam index and specific foam index for the cement-fly ash mixture.
- Calculate relative foam index.