Precast concrete units without reinforced concrete topping. Precast units include hollow-core slabs, solid slabs, or a system of precast concrete joists with timber or hollow concrete infill.

Precast concrete hollow core slabs (tropicalconcrete.com)

Precast concrete hollow core slabs (tropicalconcrete.com)

FC4_China_Dai_1

Concrete floors consisting of hollow core slabs with inadequate connections collapsed in the 2008 Wenchuan, China earthquake (J. Dai)

FC4_Canada_AdamsJ_1

Precast concrete hollow floor slab supported by concrete block masonry walls, Canada (J. Adams)