All modern buildings are invariably constructed with reinforced cement concrete. For small spans a simple RCC slab floor is generally suitable. For rooms, with the ratio of length of the room to its width is greater than 1.5, slabs are designed to span along the shorter width. That is, the main reinforcements are placed to the shorter width. The thickness of the slab depends on the type of concrete used, the span, floor loads, etc. These slabs are considered along with a frame then it is made monolithically with the supporting frames (Fig. 23.8).
Figure 23.8 RCC slab floor
If the spans of rooms are approximately equal then the slab is designed as a two-way slab (i.e., main reinforcements are placed parallel to both the spans). At corners suitable reinforcement is provided at top and bottom to take the stresses due to partial fixity.
Reinforced concrete slabs are laid adopting the routine mixing, laying, finishing and curing. The slab provides a very smooth surface at the bottom and a pleasing appearance. It also accommodates all lighting arrangements. The RCC slabs are restricted up to 4 m span beyond which beam and slab construction has to be adopted.
The following is the construction procedure:
- A centring of steel or timber is erected to support its own weight and the super-imposed load.
- The reinforcement is placed on the centring before coating a thin layer (2–5 cm) of cement concrete.
- The required mix of cement concrete is then prepared and poured around the reinforcement up to the required thickness of the slab.
- The concrete is well consolidated by ramming or using a vibrator.
- The concrete is cured for a minimum period of 2 weeks to attain its full strength.
- After concrete has sufficiently hardened, the formwork is recovered.
- The upper and lower surfaces of the slab are plastered and required finish are given.
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