The Impact of Fiber Density and Layering in NFRP on Confined Concrete Compressive Strength

Abstract

Strengthening columns hold a crucial role in structural engineering and are frequently called for due to a range of factors, including heightened load requirements, structural degradation, design flaws, or the need for seismic retrofitting. Natural Fiber-Reinforced Polymers (NFRP) in concrete reinforcement has gained significant attention in recent years as a sustainable and eco-friendly alternative to strengthened reinforced concrete. NFRP jacketing presents an adaptable option, as it delivers an improved load-carrying capability as a confining effect. This paper explores the fundamental reasons behind the need for column strengthening and the advantages of employing NFRP jacketing as a preferred method. The study examined the influence of varying fiber densities and the number of fiber layers in NFRP on the mechanical properties of concrete, with a specific focus on its confined concrete compressive strength. The test specimen was a cylinder with a diameter of 150mm and a height of 300mm. NFRP, made from abaca fiber and resin, was attached around the specimen’s circumference to provide a confinement effect. Axial load was applied to the test specimen. The findings indicated that introducing abaca fiber as an NFRP material increased confined concrete compressive strength by up to 37% compared to unconfined concrete. Additionally, the research offered valuable observations regarding the influence of varying the number of NFRP fiber layers on the behavior of confined concrete. Specifically, the study found that altering the number of layers, such as utilizing three layers of NFRP fibers, resulted in a measurable enhancement of approximately 15% in the stress experienced by the confined concrete specimen. Study findings suggest that natural fiber density and the number of layers play a role in enhancing concrete strength, however, their influence may not be significantly pronounced.