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Flowable fill is an engineered, low strength fill material you can use for a variety of construction needs. It is self-leveling, self-compacting, non-settling and has characteristics that compete favorably with traditional materials such as compacted soil, soil-cement and concrete. Flowable fill has the benefits of being easy to apply, durable and less labor intensive than competing products. Because flowable fill is fast and easy to place, you can reduce construction time and its associated costs.

In addition to the above benefits, flowable fill:

  • Eliminates excavation for underground backfill
  • Allows for narrower trenches
  • Can be excavated using conventional equipment
  • Produces no voids during placement
  • Allows for faster return of traffic loads
  • Reduces settlement and rutting under loading
  • Improves worker safety by permitting placement without entering trench

Class F fly ash is a key component of flowable fill, along with water, sand and portland cement. Its compressive strength can be designed to range from 50 to 1200 psi. Mixes in the 50 to 70 psi range have at least two to three times the bearing capacity of well-compacted earthen backfill material. Most high fly ash content mixes only require from three to five percent portland cement to develop 28-day compressive strength in the 50 to 150 psi range.


Delivered in a slurry form that resembles workable concrete, flowable fill can meet a wide variety of needs. Common applications include:

  • Sewer and utility backfill
  • Bridge abutment backfill
  • Culvert and trench backfill
  • Bedding for slabs and pipes
  • Fill for embankments, bases and sub-bases
  • Fill for abandoned storage tanks, shafts and tunnels

For more information on how you can use flowable fill with fly ash in your next construction project, contact us today.

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