Controlled Low-Strength Material (CLSM) is a self-compacted cementitious material used primarily as a substitute for compacted backfill. The material is known by many names including flowable fill, controlled density fill, unshrinkable fill and soil-cement slurry. The American Concrete Institute defines CLSM as a material with a maximum unconfined compres-sive strength of 1200 psi. For most applications, however, the compressive strength of CLSM does not exceed about 300 psi. This makes it possible for the material to be removed should future excavation be necessary.