Hollow core slabs originated their name from the circular voids or cores which run from end to the other end of the slab. The cores can be used for cable services and serve as ducts. They play a very crucial key role as they reduced the weight of the slab thus maximizing structural efficiency. A maximum capacity of 2.3 KN/sq.m over a 16m span can be achieved by using these slabs as they have a tremendous long length potential. The long-span ability is ideally suited for retail outlets, offices or car parking decks. As per the requirements of the structure, the units are fixed with or without a structural screed. The slabs that arrive on the site already have a smooth pre-finished eave. They can very useful specifically in parking structures and open structures due to its maintenance free(PCI handbook 2002). A hollow core slab consists of a precast prestressed concrete member with continuous voids which are provided to reduce the weight, indirectly reduce the cost and coupled with a benefit of concealed MEP systems which parallelly along the slab. They are predominantly used as floor or roof deck systems and can be also used for other purposes such as wall panels, bridge deck units etc.
Due to the weight saving up to a third or more the use of high strength concrete, coupled with prestressing upping means that hollow-core slabs can achieve considerably larger spans than in situ reinforced concrete slabs of similar depths. Speedy installation, reduced building, and energy costs and higher quality levels are some of the several
advantages that the hollow core elements over conventional floor casting. The width of the slab is 1.2m is standard overall with varying thickness from 150mm, 200mm, 265mm,400mm. Depending upon structural requirements. The slabs are customized.
Advantages
- Less weight
The hollow core slabs are lighter in weight compared to the custom prestressed or cast in situ slabs from 37 to 54 %. Thus the load transfer is reduced from slabs to beams and from beams to columns, thereby lowering the construction cost the Also, we have smaller dimension for foundations.
- Large spans
A span of 16 m can be bridged by hollow core slabs, thereby considerably reducing the quantity of intermediate supports required. As the length of the slab is increased, the thickness of the slab increases; also the slabs transfer the load in one direction.
- Easily Adaptable in any system of construction
The application of hollow core slabs is not only used in precast concrete structures as well as in masonry and steel construction, irrespective of the type of construction that is whether it is traditional or prefabricated.
- Raw Material Savings
50 % of concrete and 50% of the armature can be saved by incorporating the hollow core slabs as against the conventional slabs. It means that in buildings which comprise an area of 1000 m2, 35 tons of concrete and 7.5 tons of armature can be saved.
- Ease of production
1 m of traditional slabs and 2.5 m2 of hollow core slabs can be yielded by consuming the same amount of materials, manpower, and energy. In addition to this, the production of hollow core slabs is completely automated.
- Fast production
About 500 m2 of hollow core slabs can be produced in 24 hours.
- Load
Hollow core slabs can hold and retain up to 2000 kg/ m2.
- High Quality
As the production is highly mechanized and executed in strictly controlled conditions. These slabs are manufactured with the help of gliders on 150 m tracks by means of concrete extrusion method. Very high-quality steel strands are used by giving 3 times stronger than contemporary ribbed steel. The hollows are created by pipes and concrete is mechanically hardened around them. This system of manufacturing enables strict control of production methods and products.
- Hollow utilization
Hollows can be can be effectively utilized for various installation purposes.
- Fire resistance
Hollow core elements are made immune to fire by providing two levels of fire resistance.
Sound insulation: With respect to sound insulation, hollow core slabs are comparable even to the most rigorous standards, and are suitable for all types of building sectors – mainly for residential purposes.
- The short duration of time for construction
The time taken for manufacturing and transportation of hollow core precast elements is easy and quick. Moreover due to light in weight and accurate dimensions slabs can be assembled and erected on site straight from the delivery vehicle, thereby cutting the labor and the time of assembly. Precast elements can be very effective if there are number experienced team of erectors who can assemble up to 500 m2 of these slabs in one day.