A State-of-the-Art Review on Structural Strengthening Techniques with FRPs: Effectiveness, Shortcomings, and Future Research Directions.

In the pursuit of creating more sustainable and resilient structures, the exploration of construction materials and strengthening methodologies is imperative. Traditional methods of relying on steel for strengthening proved to be uneconomical and unsustainable, prompting the investigation of innovative composites. Fiber-reinforced polymers (FRPs), known for their lightweight and high-strength properties, gained prominence among structural engineers in the 1980s. This period saw the development of novel approaches, such as near-surface mounted and externally bonded reinforcement, for strengthening of concrete structures using FRPs. In recent decades, additional methods, including surface curvilinearization and external prestressing, have been discovered, demonstrating significant additional benefits. While these techniques have shown the enhanced performance, their full potential remains untapped. This article presents a comprehensive review of current approaches employed in the fortification of reinforced cement concrete structures using FRPs. It concludes by identifying key areas that warrant in-depth research to establish a sustainable methodology for structural strengthening, positioning FRPs as an effective replacement for conventional retrofitting materials. This review aims to contribute to the ongoing discourse on modern structural strengthening strategies, highlight the properties of FRPs, and propose avenues for future research in this dynamic field.

A simplified framework for orientation control of synthetic fibers in engineered cementitious composites using magnetic field.

Fiber reinforced concrete (FRC) is attracting many researchers' attention due to its excellent mechanical and fracture properties. However, its widespread implementation is hampered by the issues related to the dispersion and orientation of its fibers. According to the fracture mechanics, the reinforcement would provide maximum bridging when placed perpendicular to the crack propagation. This study is focused on the magnetic-based orientation of synthetic fibers which are mostly used in strain hardening FRC also termed as Engineered Cementitious Composites (ECC). Initially, the PVA fibers were coated with waste iron particles using a hydrothermal synthesis procedure. This was done to make synthetic fibers magnetically responsive by the formation of a physical bond between iron and PVA fibers. A solenoid was used to provide a high-intensity magnetic flux to orient these fibers in the direction of magnetic lines. Three different ECC mixes were prepared and cast in wooden molds. The molds were then placed one by one into the magnetic field for the orientation of the fibers. The fibers were successfully aligned perpendicular to the flexure cracks in only flexure dominant regions with the aid of a magnetic field. The orientation of fibers was verified with the help of microscopic images of the tortured surfaces. As a result of well aligned fibers dispersed in the ECC mix, the flexural strength was increased by 21%.