Concrete Floor Slabs
A concrete slab is a common structural element of modern buildings. Horizontal slabs of steel reinforced concrete, typically between 4 and 20 inches (100 and 500 millimeters) thick, are most often used to construct floors and ceilings, while thinner slabs are also used for exterior paving. Sometimes these thinner slabs, ranging from 2 inches (51 mm) to 6 inches (150 mm) thick, are called mud slabs, particularly when used under the main floor slabs or in crawl spaces.
In many domestic and industrial buildings a thick concrete slab, supported on foundations or directly on the subsoil, is used to construct the ground floor of a building. These can either be “ground-bearing” or “suspended” slabs. The slab is “ground-bearing” if it rests directly on the foundation, otherwise the slab is “suspended”.
For double-storey or multi-storey buildings, the use of a few common types of concrete suspended slabs are used (for more types refer to the Concrete Slab#Design section below):
- Beam and block also referred to as Rib and Block, are mostly used in residential and industrial applications. This slab type is made up of pre-stressed beams and hollow blocks and are temporarily propped until set, typically after 21 days.
- A Hollow core slab which are precast and installed on site with a crane.
- In high rise buildings and skyscrapers, thinner, pre-cast concrete slabs are slung between the steel frames to form the floors and ceilings on each level. Cast in-situ slabs are used in high rise buildings and huge shopping complexes as well as houses. These in-situ slabs are cast on site using shutters and reinforced steel.