Since 1964, flowable fill has become a popular material for projects such as

 

 

 

The flowable characteristics of this material mean it can readily be placed into a trench and into tight or restricted-access areas where placing and compacting fill is difficult. Flowable fill is used as a bedding material for pipe, electrical, telephone, and other types of conduits because the mixture easily fills voids beneath the conduit and provides uniform support. Flowable fill is used to fill large voids such as abandoned underground storage tanks, basements, tunnels, mines, and sewers. Other uses include paving sub-base, bridge abutment, and retaining wall backfill.

 

Flowable fill is an ideal pavement base material because it will not settle or rut under loads. It can be placed quickly and support traffic load within hours of placement thereby minimizing repair time and allowing a rapid return of traffic. Costs may be equal or less than the cost of using standard compacted backfill.

Like most concrete products, CDF provide many green benefits. See associated sustainability solutions and technical briefs (right) for more detail. 

 

CDF, or flowable fill is composed of water, portland cement, fine aggregate, and fly ash or slag cement. It is a fluid material with typical slumps of 10 inches or more, and has the consistency of a milk shake. Like most concrete, flowable fill may be mixed in central-mix concrete plants, ready-mixed concrete trucks or pugmills (small on-site mixers).

Once flowable fill is transported to the jobsite, the mixture may be placed with chutes, conveyors, buckets, or pumps, depending on the application. Flowable fill is placed continuously in most applications. For pipe bedding and backfilling, flowable fill is placed in lifts to prevent the pipes from floating. Internal vibration or compaction is not needed to consolidate mixtures. Its flowability and weight are sufficient for consolidation.