Composite construction consists of providing monolithic action between prestressed concrete and cast in situ concrete. This method is found to provide a greater structural efficiency compared with the conventional method of construction.

There are two methods of assembly adopted in composite construction.

• Unpropped method
• Propped method

Unpropped method

In this method the prefabricated units are made strong enough to support the dead load of wet concrete and any constructional live load and dead load due to formwork.

Propped method

In propped method the prefabricated supported on the props given during the laying as well as curing of cast in situ concrete. Here when the props are removed when the whole unit is prefabricated and cast in situ act as a monolithic unit. These are strong enough to carry the dead load and live load.

Advantages of composite construction

• Savings of Steel in a composite construction when compared to RCC members.
• Size of precast prestressed units can be reduced due to the effect of composite construction.
• Precast units also used as a support to place the cast in site slab.
• Prestressed units require less skilled labour because these are casted in the factory then they are transported to the construction site.
• Lightweight concrete provided in the cast in site slab hence it reduce the dead weight.