Characterization of a new silica alumina-based backfill material utilizing large quantities of coal combustion byproducts

► Milled fly ash as component significantly increases the workability of backfill material. ► Around 30% content of milled fly ash yields best workability of backfill material. ► Fly ash based backfill material shows good corrosion resistance in alkali, acid, salt solution. ► The silica-alumina based framework forms dense structure in backfill harden body. ► The compacted structure improves solidification/stabilization ability of heavy metal element.