Hybrid Composite With Natural and Synthetic Fibers in the Rehabilitation of Reinforced Concrete Structures

Abstract

Many concrete structures, such as buildings, civil structures, or transport facilities, have an enormous need for rehabilitation. The defects have a critical influence on the resistance and durability of these structures. This study evaluates the effectiveness of strengthening reinforced concrete structures by bonding natural fiber composite materials (hemp fiber fabrics [HFF]) mixed with synthetic fibers (carbon fiber reinforced polymer [CFRP] or Glasse fiber reinforced polymer (GFRP) composites) using epoxy-based adhesives to increase their mechanical strength and extend the lifespan of the structures. This strengthening consists of bonding a composite sheet based on natural fiber fabric to the judiciously targeted outer surface of the reinforced concrete structure. From a sustainable development perspective, replacing synthetic fibers as reinforcement with vegetal fiber plants is the first step in respecting environmental issues. This paper focuses on experimental investigations on reinforced concrete specimens (33 in all) considered strengthened by different composite mixes between natural and synthetic composite fibers. The crack propagation behavior and the influence of adhesive thickness were investigated. Considering that the adhesively bonded composite materials reduce the stress intensity at the crack tip and, therefore, increase the remaining lifetime of the concrete structure. In fact, the experimental results showed an increase in ultimate load in flexural strength from 65% to 104% of strengthened concrete specimens with hybrid (hemp and glass fiber fabrics) composite plate and from 117% to 163% of strengthened concrete specimens with hybrid (hemp and carbon fiber fabrics) composite plate, compared to the control concrete specimen without strengthening.