Flowable fill is a self-compacting, self-leveling material with a highly flowable consistently that is low strength. It is used as an economic fill or backfill. Flowable fill is an excellent solution for filling inaccessible areas, underground tanks, sewers and utility trenches since it can be placed with minimal effort and does not require vibration or manual compaction. It hardens into a crusty material with strengths less than 1200 psi, usually excavated easily if needed.
Other terms referred to this product are controlled low strength material or CLSM, unshrinkable fill, controlled density fill, flowable mortar or lean-mix backfill.