Why rebar is used at bottom and top of slab?

Rebar is used at the bottom and top of a slab to enhance its tensile and compressive strength. The bottom rebar helps resist tension forces that occur when the slab experiences bending under loads, while the top rebar provides support for compressive forces and helps prevent cracking. This placement ensures that the slab can effectively handle the stresses it encounters, improving its overall durability and structural integrity.