Over the past decade, extensive research and technology advancement with flowable fill mixtures has led to its use in numerous applications including: bedding and backfill for utility trenches, paving subbase, bridge abutment and retaining wall backfill. Recent laws passed by the EPA concerning below-grade fuel tanks resulted in increased use of flowable fill in other void-filling applications such as abandoned tanks, basements, tunnels and mines, sewers, and other underground structures.

          Flowable fill mixtures are usually comprised of combinations of cement, water, fine aggregate, and fly ash or slag. Many materials not meeting quality standards for use in concrete have been used successfully in flowable fill mixtures. Chemical admixtures specifically developed for use in flowable fill mixtures have also become more commonly used because of their unique benefits on performance properties of the mixture. The versatility in design of the flowable fill mixtures offers numerous advantages to the specifying engineer.