Abstract: A wall is formed of large, preformed structural slabs containing horizontally extending reinforcing members. The reinforcing members are made interlocking so that adjacent slabs in the same course are locked together horizontally. The slabs are placed in the wall vertically aligned, so that the reinforcing members and locking means (which extend outside the preformed concrete slabs) of slabs of successive courses can be welded together, giving a skeleton of steel which imparts great strength and earthquake resistance to the structure. Preferably, the structure is a silo and the slabs are arcuate.