Reinforced Cement Concrete (RCC) Floors

RCC floors are becoming extremely popular in the construction of modern buildings since of the inherent benefits of this type of construction. Concrete, though strong in compression, is weak in tension. Thus, it is suitably reinforced along with the help of mild steel bars that take the whole bending tension. Because of this, the overall thickness of RCC floors is comparatively little, thereby reducing the self weight of floor itself. RCC floors are also moderately fire proof and damp proof. The technique of construction is also simple except which centering is needed. These floors could also be used on large spans and, thus, more suitable for big size rooms, halls etc.

In RCC flooring, a RCC slab bends downwards, causing tension at the bottom fibres. Because of this mild steel bars reinforcement is placed at the bottom of the slab, remaining a minimum clear cover of 15 mm. Half these bars are bent up near ends to take up negative bending moment caused due to partial fixidity at the ends. This main reinforcement is placed within the direction of the span of the slab that is equal to the width of the room, especially while the length of the room is more than 1.5 times the width of the room. Like a slab is known as one way reinforced slab. Nominal reinforcement (called as temperature/distribution reinforcement) is placed in the perpendicular direction. Hooks are placed at the end of each plain bar, by these are not needed in ribbed bars (tor-reinforcement). The bearing of the slab in the wall should neither be less than its thickness, nor less than half the width of the wall. Figure 9(a) shows one way reinforced slab. Like slabs are quite suitable and economical for spans up to 5 m.

The slab is cast on timber or steel shuttering. After erecting the centering, properly bent reinforcement is placed in position. Distance pieces of stone or concrete are placed among the reinforcement and the shuttering plate so that proper cover is managed. Cement concrete of appropriate mix(commonly 1 : 2 : 4) is then poured and well-compacted. The slab is then properly cured. Shuttering is removed only while the concrete has fully set.

While the length of the room is less than 1.5 times the width of the room, the slab spans bends in both the directions. It is essential to provide reinforcement in both the directions. Such a slab is known as a two-way reinforced slab, such as the one displays.At the corner, suitable mesh reinforcement is provided at the top and bottom, to prevent their lifting.

While the width of room becomes more, the span of slab increases, and simple RCC slab becomes uneconomical. In which case, the floor structure consists of RCC beams and slabs cast monolithically. The beams, known as T-beams, act as intermediate supports to the slab that is continuous over these beams. While the size of the room (i.e. hall) is extremely large, these floor beams are supported on longitudinal beams which, in turn, are either supported on RCC columns or end walls. Figure 10 shows details of beam slab flooring.