| Summary: | In the last two decades, the use of voided (bubbled) slabs in constructions has been increased because of several advantages such as light self-weight, cost-saving, and accelerated construction schedules. However, the structural behavior of such slabs has not been adequately inspected, especially for one-way slabs. Therefore, this paper presented an experimental investigation to assess the effect of voids’ size on the structural behavior of one-way slabs. Four slabs were fabricated using self-compacting concrete. Three of them were bubbled slabs, containing 68 polystyrene balls with different sizes (60 mm, 70 mm, and 90 mm); these balls were regularly distributed inside the slabs. The fourth slab was conventional solid without balls and assigned as a control slab. The presence of balls led to reducing the self-weight of slabs, by about 6.4%–21.6%, compared with the solid slab. The slabs were subjected to the four-point loading up to collapse. The results stated that the use of balls with a size of 60 mm, which is equal to half thickness of slab, was the optimum where the reduction in the strength, compared to the control slab, was approximately nonexistent and the drops in stiffness, ductility, and toughness were relatively slight, smaller than 11.1%. For other sizes, the influence of balls became significant, especially for balls with a diameter of 90 mm where the reductions in strength, stiffness, ductility, and toughness reached, respectively, 21.3%, 23.7%, 67.0%, and 79%, in comparison with the control slab. Also, using 90 mm- diameter balls changed the failure mode from flexural to shear. Finally, the flexure and shear strengths of the slabs were determined per the ACI 318M-19 and EC2 codes. The predictions of the EC2 code were more accurate and less conservative than those of ACI 318M-19 code. Keywords: Voided slab, Polystyrene balls, One-way slab, Ultimate strength, Ductility, Stiffness, Toughness
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