A hollow core slab, also known as a voided slab, hollow core plank or simply a concrete plank is a precast slab of prestressed concrete typically used in the construction of floors in multi-story apartment buildings. The slab has been especially popular in countries where the emphasis of home construction has been on precast concrete, including Northern Europe and former socialist countries of Eastern Europe. Precast concrete popularity is linked with low-seismic zones and more economical constructions because of fast building assembly, lower self weight (less material), etc.
The precast concrete slab has tubular voids extending the full length of the slab, typically with a diameter equal to the 2/3-3/4 of the slab. This makes the slab much lighter than a massive solid concrete floor slab of equal thickness or strength. The reduced weight is important because it lowers the costs of transportation as well as material (concrete) costs. The slabs are typically 120 cm wide with standard thicknesses between 15 cm and 50 cm. Reinforcing steel wire rope provides resistance to bending moment from loads.