Construction of a Concrete Slab:

a Concrete Slab is a common structural element in modern buildings.

In many Residential 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.

Concrete slabs are built on the building site using formwork - a type of boxing into which the wet concrete is poured.

Plastic tipped metal are used to hold the rebar away from the bottom and sides of the form-work so that when the concrete sets it completely envelops the reinforcement.

Slabs can either be ground-bearing or suspended.

  • Ground-Bearing Slab: The form-work may consist only of sidewalls pushed into the ground.


  • Suspended Slab: The form-work is shaped like a tray,often supported by a temporary scaffold until the concrete sets.


Design of a Slab:

For a suspended slab, there are a number of designs to improve the strength-to-weight ratio. In all cases the top surface remains flat,and the underside is modulated with either a corrugated,ribbed or waffle design

  • Corrugated:

Corrugated slabs are created when concrete is poured into a wavy metal form,this improves strength and prevents the slab from bending/sagging under its own weight.

The corrugations run across the short dimension from side to side.


  • Ribbed slab:

Ribbed floors consisting of equally spaced ribs are usually directly supported by columns giving considerable extra strength on one direction.


  • Waffle slab:

Reinforced concrete footing and slab system constructed on ground consisting of a perimeter footing (edge beam) and a series of narrow internal beams (strip footings) at one metre nominal centres running each way.


  • Reinforcement Design:

The slab is to be reinforced with rebars (reinforcing bar) or better known as reinforcing steel and reinforcement steel are positioned within the formwork before the concrete is poured in.


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