Construction Cost Estimating


How to design different types of concrete slabs

Reinforced Cement Concrete Slab

• A Reinforced Concrete Slab belongs to one of the most vital structural element in present building industries. The columns and beams provide support to the concrete slabs.
• The density of RCC Slabs varies from 10 to 50 centimeters and these are frequently applied for building up the floors and ceilings.
• Thin concrete slabs are also utilized for external paving purpose.
• In various domestic and industrial buildings, a dense concrete slab that is supported on foundations or directly on the sub soil, is employed for developing the ground floor of a building.
• Slimmer, pre-cast concrete slabs are casted among the steel frames to build up the floors and ceilings on each level in high rises buildings and skyscrapers.
• At the time of creating structural drawings of the reinforced concrete slab, the slabs are shortened to “r.c.slab” or simply “r.c.”.

Design of different types of slabs and their reinforcement

In a suspended slab, various types of designs exist to enhance the strength-to-weight ratio. In all cases the top surface stays flat, and the base is modulated:

• Corrugated – It is normally used where the concrete is poured into a corrugated steel tray. It makes the strength better as well as resists the slab bending under its own weight. The corrugations come upon the short dimension, from side to side.
• A ribbed slab – It provides supplementary strength on one direction.

• A waffle slab – It provides extra strength in both directions.

Reinforcement design
• A one way slab provides structural strength in shortest direction.
• A two way slab provides structural strength in two directions.

These slabs come as cantilevered or Simply Supported Slabs.


• A concrete slab is casted in two different ways like I prefabricated or cast in situ.
• Prefabricated concrete slabs are casted in a factory and then transmitted to the site for dropping into place among steel or concrete beams.

• These may be pre-stressed (in the factory), post-stressed (on site), or unstressed. Precautions should be taken to verify that the proper dimensions are followed to construct the supporting structure to get rid of the issues concerning setting of slabs over the supporting structure.
• In situ concrete slabs are constructed on the building site with formwork. Formwork belongs to a box-like setup in which concrete is flowed for building up the slabs.
• The reinforcing steel bars are arranged inside the formwork for reinforced concrete slabs and then the concrete is poured.
• The reinforcing steel bars are retained ahead of the bottom and sides of the form-work with the help of plastic tipped metal, or plastic bar chairs, so that when the concrete is placed it completely encircles the reinforcement.
• Formwork changes with the type of slab. For a ground slab, the form-work may include only of sidewalls which are pushed into the ground but for a suspended slab, the form-work is formed like a tray, frequently supported with a temporary scaffold unless the concrete is placed.

To gather more information on formwork, go through the following link

How to design different types of concrete slabs