Flowable Fill is a self-compacted, cementitious material used primarily as a backfill in place of compacted fill. It is a blend of cement, sand and water, and is also known as controlled low strength material, controlled density fill, K-krete, and unshrinkable fill.

Fly ash ground granulated blast furnace slag, or high air generators are added to the mix to ensure low maximum compressive strengths. Flowable Fill materials have a compressive strength of 1200 PSI or less. Most current applications require a 28-day compressive strength of 100 PSI or less. This lower strength requirement allows for future excavation with conventional excavation equipment.

Flowable Fill is widely used in backfilling utility trenches and other road-cuts. It can also be used in road base, mud slabs, slope stabilization, and sinkhole repair. Most have bearing capacities comparable to conventional compacted fill. Special load bearing and permeability properties can be designed to meet any requirement. Flowable Fill is non-conductive and non-corrosive to PVC and/or ductile iron pipe.