Using Bubbles in the slab is a revolutionary method of eliminating concrete from the middle of conventional slab as this concrete does not perform any structural function, thereby dramatically reducing structural dead weight. This research presents experimental study to investigate the effect of construction type on the strength and behaviour of bubbled one-way slabs. The experimental program consists of testing four slabs with dimensions of 1850mm×460mm×110 mm. One1of the tested slabs was conventional slab (without bubbles), two bubbled slabs with different types of construction (simple and filigree bubbled slabs) and the remaining one is filigree bubbled slab strengthened with steel cage. The bubbles were made of recycled plastic balls. The experimental results show that the stiffness reduction factor for all the bubbled slabs was (0.87), this leads to decrease the ultimate strength of bubbled slabs and to be smaller than that of the solid slab by 4.4% 69% and 1.7% respectively. Also an increase in deflection at yield load (∆y) by about (10% to 12%), at the same time the crack load is found to be decreased by (13% to 40%). The simple bubbled slab is more efficient when compared with filigree bubbled slab. Also the results show that the use of steel cage in filigree bubbled slab gives an increase in the ultimate load by 69% and an increase in the ultimate deflection by about 77% when compared with filigree bubbled slab without steel cage.
This paper presents an experimental investigation on the structural performance of hollow-core reinforced self-compacting concrete beams and performs an optimization analysis to select the optimum hollow-core beam section, as well as perform a sustainability analysis. The experimental program includes constructing and testing five beams with different longitudinal hollow-core diameters created by using recycled plastic pipes, as well as a solid beam, used as a reference specimen. The results show that it can reduce the concrete from self-compacting concrete beams with percentages from 5.4 to 14.2 with a decrease in the first crack load from 9.1 to 22.7% and the ultimate strength from 2.3 to 10.5% respectively compared to the reference solid beam. The optimization analysis shows that the beam of 46 mm diameter hollow-core is the optimum selection in the concrete volume reduction of 11.1%, cracking load, and ultimate load reduction of 13.6% and 9.3% respectively among all the other beam specimens. While the sustainability analysis reveals that, using longitudinal voids of diameters from 32 to 52 mm leads to a decrease in the embodied energy with percentages from 5.4 to 14.2% and carbon dioxide emission with percentages from 5.4 to 14.1% respectively. Increasing the longitudinal void diameter makes hollow-core self-compacting concrete beams more ductile and exhibits large deflections before failure occurrences. Article Highlights Tests on hollow-core reinforced self-compacting concrete beams are conducted. Recycled plastic pipes are used to create hollow-core in the beams and to reduce ineffective concrete. Reducing ineffective concrete contributes to sustainability with maintaining a good ratio of beam strength.
Hollow-core slab (HCS) is a voided slab that has longitudinal voids made by recycled plastic pipes that were placed in the middle of the slab thickness where the flexural stress is minimum. These longitudinal voids can reduce the volume of slabs to more than 30% which leads to save raw materials and satisfying sustainability, economic considerations, and a clean environment. The experimental program comprised casting six slabs with dimensions of 1700mm × 435mm ×125mm, one of them was solid slab as a reference slab and the other five slabs were HCSs. These slabs were divided into two groups, the first group consisted of three HCSs with different numbers of longitudinal voids, and the second group consisted of three HCSs with different diameters of longitudinal voids. The results of the test showed that increasing numbers of longitudinal voids can save the ultimate load with percentages 93.47%, 87.63%, and 82.92%, with increasing the ultimate deflection by 8.72%, 21.57%, and 28.31%. Also, increasing the diameter of longitudinal voids can save the ultimate load with percentages 93.37%, 90.01%, and 87.63% and increase the ultimate deflection by 6.58%, 13.26%, and 21.57% respectively when compared with the reference slab.
This research presents an experimental study to investigate the effect of coarse aggregate maximum size on the shear behavior of self-compacting concrete (SCC) and conventional concrete (CC) slender beams having the same compressive strength and make a comparison between the shear behavior of concrete beams. The experimental program included casting and testing eight beams with a constant size of 150mm height ×125mm width×1000mm length. Two coarse aggregate maximum sizes were used (10mm and 20mm) with SCC and CC in normal and high strength concrete. The results showed that increasing the coarse aggregate maximum size from 10mm to 20mm results in a slight increase in the diagonal cracking load and ultimate shear strength of SCC beams, while for CC beams the result was more significant. Also, it was found that the effect of increasing the coarse aggregate maximum size was more significant for normal strength as compared with high strength beams for both concrete types. Furthermore, the comparison between the shear behavior of SCC and CC beams having the same compressive strength and a concrete with the same coarse aggregate maximum size revealed that the SCC exhibited less diagonal cracking load and less ultimate strength compared with CC.
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