The slab is a structural element, it is intended to serve as a separation between consecutive floors of a building. There are solid and lightened reinforced concrete slabs. The solid ones are used for smaller spaces and are filled throughout their volume, that is, they do not have empty spaces as it happens with the lightened ones. Lightened slabs are built by leaving empty spaces under their lower face so that they have less concrete and are lighter; this allows them to be used in larger spaces (with a greater distance between supports).