A big day at the construction site...THIRD FLOOR !!!

A hollow core slab , also known as a voided slab or hollow core plank is a precast slab of prestressed concrete typically used in the construction of floors in multi-story apartment buildings. 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 floor slabs of equal thickness or strength. Reduced weight is important because of transportation cost and less cost of material (concrete). The slabs are typically 120 cm wide with standard thicknesses between 15 cm and 50 cm. The precast concrete I-beams between the holes contain the steel wire rope that provide bending resistance to bending momentum from loads. Slabs are usually produced in lengths of about 120 meters. The process involves extruding wet concrete along with the prestressed steel wire rope from a moving mold. The continuous slab is then cut by big diamond circular saw according to the lengths (and width) required on blueprint. Factory production provides the obvious advantages of reduced time, labor and training. To meet modern standards (both hollow-core and massive slab) of soundproofing the floor needs to be covered with a soft floor covering that is able to dampen the sound of footsteps. An alternative is to use a thin "floating" slab of concrete insulated from the voided slabs.