Fill Flow

  • Overview
  • Packaging
  • FAQs
  • Advantages
  • Resources

Fritz-Pak’s flowable fill admixture, Fill Flow, uses a powerful foaming agent to create durable, cost-effective controlled low-strength materials used for backfilling utility trenches. When added to the concrete mix, it generates a significant amount of entrained air to lower the overall compressive strength of the mix. This reduces the amount of water required for these mixes, lowering the risk of excessive bleed water that has to be pumped out of the trench. As a flowable fill admixture, Fill Flow increases the volume of material in the truck. In order to prevent spills during transit, this admixture should be added at the job site. Fill Flow does not contain hazardous materials and it comes packaged in our signature, water-soluble bags for easy dosing.

Benefits of a Flowable Fill Admixture

If you want to see how using Fritz-Pak’s flowable fill admixture compares to more traditional control low strength mix designs, check out the product demonstration video below. Don’t forget to follow our social media channels for more information about how our admixtures can improve your concrete.

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What kind of admixture is Fill Flow?
It is a very high strength surfactant that causes air bubbles to form in high mineral concentration solutions, such as cement pastes.
How does Fill Flow work?
It creates billions of air bubbles that serve as "ball bearings" within the flowable-fill and increase the flow properties.
What kind of unit weight can I expect wih Fill Flow?
Unit weight is dependent on mix design and size of sands. Typically you should expect a unit weight of 90-120 lbs./cu.ft.
What is the recommended addition procedure for Fill Flow?
It should be added at the jobsite. Fill Flow will increase the volume and flowing properties of the flowable fill. If added at the plant, the possibility of spills during transport are increased.
Compared with flowable fill without any admixtures, do I need more or less water to produce flowable fill with Fill Flow?
You will need less water. Typically you will only use 25-30 gallons of water per cubic yard of flowable fill.
Since I am increasing the air content of the flowable fill with Fill-Flow, will I also experience a reduction in strength of the flowable fill?
No. You are increasing the air content, but you are also reducing the water content. As you reduce the water-cement ratio, the cement paste increases enough strength to compensate for the increased air content.
Can Fill Flow be used in mixes containing other cementitious materials, besides cement, such as fly ash or granulated blast furnace slag?
What standards does Fill Flow meet?
Currently there are no national standards for additives for flowable fill. Most states have specifications for the flowable fill produced, not necessarily for the type of admixture used to produce it.
Can Fritz-Pak help me develop a flowable fill mix design?
Are there any additional benefits to using Fill Flow?
Yes, flowable fill produced with Fill Flow is more pumpable, it discharges from the ready mix truck faster and also the truck is easier to clean.
For pumping flowable fill long distances, what do you recommend?
Besides making the flowable fill with Fill-Flow we recommend adding one bag of Slick-Pak II for every 3 yards to improve pumpability.
  • Patented water-soluble Fritz-Pak bag readily breaks down even in very fluid mixes.
  • Easy handling and storage because Fill Flow is a dry powder, not a liquid.
  • No problems with leakage, heat damage, or freezing.
  • Produces an extremely fluid material with minimal shrinkage or segregation.
  • Controlled Low Strength Material (CLSM) can be placed directly from the ready mix truck.
  • Eliminates the need for compaction of layered backfill.
  • Produces very stable air content.
  • Significantly faster and less labor intensive than compacted soil fill.


Fill Flow is compatible with all conventional CLSM materials. Fill Flow contains no calcium chloride or other corrosive agents. Superplasticizers, water reducers and dispersants may reduce the effectiveness of Fill Flow.