This paper identifies many of those features that distinguish flowable fly ash from other backfill materials, both conventional and controlled low-strength materials (CLSM). The physical properties of the flowable fly ash (using Type F ash) that are discussed are also provided with physical units that define these same properties. These characteristics include its resistance in both a fresh plastic and a hardened state to erosion from flowing water; this resistance to erosion from water normally allows the material to be placed directly into water without the need for tremies. Flowable fly ash, using either dry or conditioned fly ash, can be mixed in ready-mix trucks, pug mills or turbine mixers. Flowable fly ash can be placed by chutes from ready-mix trucks, by end-dumping from conventional trucks or conveyors, or by pumping. The material can be competitive in cost and has been used in many applications in which its advantages in properties, scheduling, and elimination of hazards to manual labour have far outweighed those of other conventional backfill materials.
Abstract