THE EFFECT OF BALLS SHAPES AND SPACING ON STRUCTURAL BEHAVIOUR OF REINFORCED CONCRETE BUBBLED SLABS

Abstract

Reinforced concrete slab with plastic voids (Bubbled-Deck system) is a new type of slabs which has two-dimensional arrangement of voids within the slab that is developed to decrease the slab self-weight while maintaining approximately the same load carrying capacity as it compared with the solid slabs. Plastic voided slabs have the ability to reduce the concrete amount by about 30 percent, this reduction is so important in terms of cost saving and enhancement the structural performance. This research presents experimental study to investigate the effect of ball shapes (spherical and elliptical) and spacing between balls in cross section (25 and 70mm) on the strength and behaviour of this kind of slabs. The bubbles were made using recycled plastic balls. The experimental program consists of casting and testing five slabs with dimensions of 1850mm×460mm×110 mm. The experimental results show that the bubbled slabs (containing spherical and elliptical balls) have about 90% to 96% of the ultimate load of the solid slab and an increase in the deflection at ultimate load by 7.8% to 21%, at the same time the first crack load decreases by about 6.7% to 16% as it compared with that of the solid slab. Also the results show that bubbled slabs having spherical balls are more efficient in bearing loads  than that having elliptical balls with the same amount of concrete reduction.