Mechanical Properties of Hybrid Steel-Polypropylene Fiber Reinforced High Strength Concrete Exposed to Various Temperatures

Abstract

Combining different types of fibers inside a concrete mixture was revealed to improve the strength properties of cementitious matrices by monitoring crack initiation and propagation. The contribution of hybrid fibers needs to be thoroughly investigated, taking into consideration a variety of parameters such as fibers type and content. In this paper, the impact of integrating hybrid steel-polypropylene fibers on the mechanical properties of the concrete mixture was investigated. Hybrid fiber-reinforced high-strength concrete mixtures were tested for compressive strength, tensile strength, and flexural strength. According to the results of the experiments, the addition of hybrid fibers to the concrete mixture improved the mechanical properties significantly, more than adding just one type of fiber for specimens exposed to room temperature. Using hybrid fibers in the concrete mixture increased compressive, tensile, and flexural strength by approximately 50%, 53%, and 46%, respectively, over just using one type of fiber. Furthermore, results showed that including hybrid fibers into the concrete mixture increased residual compressive strength for specimens exposed to high temperatures. When exposed to temperatures of 200 °C, 400 °C, and 600 °C, the hybrid fiber reinforced concrete specimens maintained 87%, 65%, and 42% of their initial compressive strength, respectively. In comparison, the control specimens, which were devoid of fibers, would be unable to tolerate temperatures beyond 200 °C, and an explosive thermal spalling occurred during the heating process.

Effect of hybrid-fiber- reinforcement on the shear behavior of high-strength-concrete beams

“…It can be computed by dividing the ultimate deformation that occurs at the ultimate shear force by the cracking deformation that occurs at the cracking shear force (Pakravan et al, 2016;Yan et al, 2021). The fact that when the hybrid fibers were added, the cracking and ultimate shear strengths increased supports their ability to withstand macro and micro cracks at different stress levels, delaying the cracking process and improving stiffness and strength (Tahenni et al, 2016;Sivakumar et al, 2020;Ismail and Hassan, 2021;Shaaban et al, 2021;Yang et al, 2021;Tawfik et al, 2022). The increase in ultimate deformation and ductility values is a further indication of the efficacy of hybrid fibers in reducing concrete's brittleness and improving its capability for plastic deformation without fracture.…”

“…Additionally for the significance of these fibers in enhancing concrete's behavior in resisting tensile stresses and minimizing the formation and propagation of cracks. The findings of earlier studies demonstrated that utilizing hybrid fibers enhanced concrete strength and durability as well as minimized cracks compared to using a single type of fiber (Hoang and Fehling, 2017;Li et al, 2018;Zhang et al, 2018;Ali et al, 2020;Sivakumar et al, 2020;Zhong et al, 2020;Tawfik et al, 2022). Tawfik et al (2022) observed that using hybrid fibers rather than only one kind of fiber increased the strength of the composite in terms of compressive, flexural, and tensile stresses by 50%, 46%, and 53%, respectively.…”

“…The findings of earlier studies demonstrated that utilizing hybrid fibers enhanced concrete strength and durability as well as minimized cracks compared to using a single type of fiber (Hoang and Fehling, 2017;Li et al, 2018;Zhang et al, 2018;Ali et al, 2020;Sivakumar et al, 2020;Zhong et al, 2020;Tawfik et al, 2022). Tawfik et al (2022) observed that using hybrid fibers rather than only one kind of fiber increased the strength of the composite in terms of compressive, flexural, and tensile stresses by 50%, 46%, and 53%, respectively. This improvement in strength is caused by the incorporation of hybrid fibers with various characteristics, which stop the development of multiscale crack formation at various levels of stress.…”

High-Temperature Behavior of Polyethylene-Terephthalate-Fiber-Reinforced Sand Concrete: Experimental Investigation

“…The study of concretes containing fibers shows, in the presence of polypropylene, a decrease in the vapor pressure peak with the rise in temperature. This decrease is related to the volume of fibers [12][13][14][15]. The study of the influence of metal fibers on the behavior of concrete brought to high temperature shows for some authors a thermal instability at low temperature (below 200 • C) or delayed instability (from 800 • C) [16,17].…”

“…Several parameters may be at the origin of the observed differences: the mode of hardening of the specimens (dry or saturated specimens); the heating rate; and the fiber content, which seems to be a preponderant factor [18]. The high quantity of fibers can also generate an additional thermal gradient, which would lead to the phenomenon of thermal instability [12,14].…”