Effects of Steel Fibers Geometry on the Mechanical Properties of SIFCON Concrete

This research aims to shed light on the effect of steel fiber shape, length, diameter, and aspect ratio on the mechanical properties of slurry infiltration fiber reinforced concrete (SIFCON). This study comprised of casting and testing three groups of SIFCON specimens with 6% fiber volume fraction. The first group was reinforced with micro steel fiber, other reinforced by hook end steel fibers, while the last group of specimens reinforced by mixing two shape of steel fiber as hybrid fiber (3% micro steel fiber +3% hook end steel fiber). Silica fume was used as a partial replacement (10%) by weight of cement. 3.7% super plasticizer was used to make the slurry liquid enough to penetrate through the fiber network, while the w/c ratio kept constant at 0.33. It was found from the results achieved that the compressive strength, static modulus of elasticity, splitting tensile strength and toughness are extremely affected by the geometry of fibers because the network of fibers formed and their density depends on the size and shape of fibers. Where the values of micro steel fibers are far outweighing the values of hooked end fibers. It was also deduced from empiricism results that combining long and short fibers gives excellent results

Punching shear behavior of flat slabs utilizing reactive powder concrete with and without flexural reinforcement

This article investigates the effect of flexural reinforcement and ultrafine steel fiber on the punching shear of reactive powder concrete (RPC) slabs with different thicknesses. Ten RPC slabs and two normal-strength concrete (NSC) slabs were cast and tested with dimensions of 520×520 mm. According to test parameters, these slabs were arranged into three sets. These parameters were the percentage of ultrafine steel fiber, presence/absence of flexural reinforcement, and thickness of the slab. All slab specimens were simply supported along the four edges and concentrically loaded by a square plate with dimensions of 70×70 mm. The experimental results indicated superior and higher performance for RPC slabs compared with NSC slabs in which the punching shear resistance of RPC slabs increased by 78.8%, 92.5%, and 100.8% for RPC slabs containing steel fibers of 1%, 1.5%, and 2%, respectively, as compared with NSC slabs with the same thickness. Also, the presence of flexural steel reinforcement in the slab resulted in a higher ultimate punching shear strength compared with the similar slab without flexural steel reinforcement. Moreover, with increasing the slab thickness, the ultimate punching shear increased significantly and the ultimate deflection decreased as the flexural rigidity of the section increased. Finally, the results showed that it is possible to produce thin RPC slabs with 2% microsteel fibers and without flexural reinforcement to able to sustain the ultimate load, which are comparable with reinforced and nonreinforced normal concrete slabs, which is very crucial for designers who need to reduce the reinforcement amount required with beneficial effects on the cost and self-weight reduction for many structural applications