waffle slab is a concrete slab made of reinforced concrete with concrete ribs running in two directions on its underside.
The name waffle comes from the grid pattern create by the reinforcing ribs. Waffle slabs are preferred for spans greater than 12 m, as they are much stronger than flat slabs, flat slabs with drop panels, two way slabs, one-way slabs, and one way joist slabs.
Characteristics of Waffle Slab
Waffle slabs are generally suitable for flat areas. The volume of concrete used is much lower compared to others.
The reinforcement on the waffle slab is provided in the form of mesh or individual bars.
A separate digging for beams is not required for waffle slab.
The bottom surface of the slab looks like a waffle that is obtained by using cardboard panels or pods, etc.
The recommended waffle slab thickness is 85-100mm, while the total slab depth is limited to 300-600mm.
The ribs provided on the waffle slab are generally 110 to 200 mm.
The recommended spacing of the ribs is 600 to 1500 mm. Reinforced waffle slabs can be built for a span of up to 16 meters, while beyond that length precast waffle slab is preferable.
shrinkage and is lower than rigid rafts and footing slabs.
The waffle slab requires only 70% of the concrete and 80% of the steel in the concrete and steel used for the rigid raft.
Construction Process of Waffle Slab
A waffle slab can be made in different ways, but generic shapes are needed to give the slab a waffle shape. The formwork is made up of many elements: waffle sleeves, horizontal supports, vertical supports, cubic joints, hole plates, clits and steel bars. First the supports are built, then the sheaths are put in place and finally the concrete is poured.
This process can occur in three different approaches, however the basic method is the same in each:
On-site - Formwork construction and concrete pouring occur on site, then the slab is assembled.
Prefabricated Process -slab while manufacturing, without the need to reinforce the assembly on site. This is the most expensive option.
precost -Slabs are manufactured elsewhere and then taken to site and assembled.
Adadvantages of Waffle Slab
Shapes can be implemented with wood, concrete, or steel.
It's best for buildings that require less vibration this is accomplished by the by directional joist reinforcements that make up the grid.
A proprietary implementation of this system is called Holedeck.
Larger sections can be achieved with less material, being more economical and respectful with the environment.
Some people find the waffle pattern to be aesthetically pleasing.
Greater load capacity than traditional one-way slabs.
If holes are provided between the ribs, construction services can be run through them.
Disadvantages of Waffle Slab
Topographic areas not sloping sites.
Waffle slabs are thicker than flat ones, so the height between each floor must be greater to have enough space for the slab system and other construction services.
Larger amounts of formwork materials are required, which can be very expensive.