Fibers have been considered an effective material that was used to improve the concrete's weak properties, namely its tensile strength, ductility, and crack resistance. Thus, the current study highlights two major objective, the former is the fibers shapes and types on the mechanical properties of the fresh and hardened concrete while the latter explores the impact of the fiber contents on the concrete mechanical properties developments. To achieve these targets six types of fibers (five of them made of steel and the last was polyolefin fibers) with various shapes are utilized. The tests were carried out to investigate the fibers shape and material contribution in the concrete mix properties improvement. The samples were subjected to destructive and non-destructive tests such as workability, compression, bending, and splitting. The non-destructive tests include ultrasonic pulse velocities and the Schmidt Hammer test. Three kinds of fibers (two of steel and one of polyolefin fiber) are used with variable content ratios of 0.5, 0.75, 1.0, and 1.5% to study the fiber content effect. Generally, the workability of fresh concrete has a reverse relationship with fiber presence and fiber content ratios. The compressive capacity, splitting and flexural strength has a direct proportion with fibers contents. The hooked steel fibers appeared the best results in terms of shape comparison. Doi: 10.28991/CEJ-2022-08-11-07 Full Text: PDF

In this research, the structural behavior of reinforced concrete brackets cast with concrete containing different types of fibers was studied. Seven samples of reinforced concrete corbels were cast and tested. One specimen was cast without fiber as a reference, and the other samples were made with six different types of fibers at a constant volume fraction (1% of the total concrete volume). The fibers used in the research were made of two different materials: steel and polyolefin. One specimen was cast with polyolefin fiber, and in the five remaining samples, steel fiber was used. Straight, crimped, and three different dimensions of hooked fiber were used. The results showed that the corbels with straight and hooked end steel fiber (6, 5, and 3 cm length), crimped steel fiber sized 3 cm, straight steel fiber sized 12 mm, and straight polyolefin fiber sized 6 cm showed 69.2%, 57.7%, 38.5%, 61.5%, 92.3%, and 100% higher cracking loads than the control corbel made with normal concrete, respectively, as well as exhibiting (51.7%, 48.3%, 31.0%, 24.1%, 12.1%, and 3.4%) higher ultimate loads than the control corbel. From these results, it can be concluded that the shape of the steel fiber clearly affects the ultimate load. For the same length, and despite the lack of aspect ratio, steel fibers gave an increase in the maximum load of 46.6% when compared with polyolefin fibers. Doi: 10.28991/CEJ-2022-08-03-08 Full Text: PDF

Polyolefin fiber is a new type of fiber that was used in concrete to improve some of the poor properties of concrete including; tensile strength, ductility, and fracture energy. In this research, the contribution of Polyolefin fiber in improving the properties of hardened concrete was examined by adding polyolefin fibers to mix with different fiber content. The polypropylene fibers were added as a ratio of 0.5, 0.75, 1.0, 1.5, and 2% of concrete volume. Destructive and non-destructive tests were carried out: slump, compression, splitting, and bending, Schmidt Hammer, and ultrasonic pulse velocity tests. The results showed that, as the polyolefin fiber content increases, the workability of concrete reduces dramatically. The experimental findings demonstrate that the concrete tensile strength and ductility were improved by a small improvement in overall compressive strength. The results show that the compressive strength increased gradually with the increase in fiber content of up to 1.5%, and then, the compressive strength starts to decrease. However, the tensile strength increases continuously with the fiber content increasing. A good relationship was obtained between the destructive and nondestructive tests.

No abstract