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How are concrete suspended slabs built?

November 1, 2020

Suspended slabs are upper floor slabs that are not in direct contact with the ground and form the roof or the floor above the ground level. They usually form the upper stories house floors but can also be laid on top of a pre-built wall to form a floor. Concrete slabs come in many forms and can be used to provide great thermal comfort. Concrete as a material with high embodied energy is the most common material used for slabs construction.

concrete suspended slabs

Types of slabs

There are three types of suspended concrete floor systems which defer in the way they are constructed, precast suspended slabs, cast in-situ and composite concrete/steel.

          Composite Concrete/Steel Slab 

Composite Concrete/Steel Slab is a slab where steel decking acts as non-recoverable formwork and partial reinforcement for the floor slab. The decking spans one way and will usually be continuous over several supports. Single spans are, however, common and acceptable. Support is as for in-situ floors.

          Precast Concrete Suspended Slab 

Precast concrete suspended slabs are constructed off site and later are craned into the construction site. This type uses precast concrete panels or planks spanning only in one direction. A concrete topping is usually required, sometimes for structural purposes and therefore reinforced, only to provide a level surface for the application of floor finishes. The best approach is manufacturing a complete high-quality precast concrete in a restrained environment. In some cases, after the complete finished concrete slab is manufactured in a factory and placed on site, an additional thin concrete pouring is needed over the top.

The concrete is poured after the reinforcement is placed in reusable and adjustable moulds. If the complete construction finishes in factory, polishing, grinding and dying can be applied.

The complete concrete elements are transported to the site and then are placed to position.

Precast slabs can be made from conventional or post-tensioned reinforced concrete, or from autoclaved aerated concrete (AAC). You can find more information about autoclaved aerated concrete here.

Precast Concrete Suspended slab

          Cast in-situ Concrete Suspended Slabs 

Cast in-situ or also known as poured in place concrete is a technique that is performed directly on the construction site. This methodology involves non-hardening concrete transport in pre concrete trucks to the construction site.  The concrete is placed on position into the form with a pump. Once the concrete has cured sufficiently so it has enough strength to be self-supporting, the formwork and the false work are removed, and the slab doesn’t move because it is built in its final place. In-situ concrete has been used for many years but other forms of construction incorporating components have become very popular as well, because of the significantly reduced cost of conventional formwork, on-site activity and construction time.

Cast-in-situ Concrete Suspended Slabs

Still in-situ concrete suspendend slabs are the most flexible type of floor slabs that can carry walls of any type and anywhere in their span without restrictions by position of the walls (room plans) below them. With in-situ floors, the support for the planks can take a variety of forms. These floors are independently constructed for particular construction projects. Support may take the form of walls or beams, themselves supported either by beams or columns.

The professional construction contractor plays a valuable role for constructing an accommodation that lasts a lifetime. That is why it is very important to choose an appropriate and high-quality dedicated contractor for your construction projects.

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