External para-aramid fibre - concrete reinforcement

Purpose – This research seeks to investigate the potential of using para-aramid fibre fabric and yarn as an external reinforcement to existing structures. The purpose of this paper is to improve existing structural performance or to return the original design performance, during refurbishment. The research aims to investigate the potential for enhanced flexural strength and toughness in concrete beams, which may be required for change of use of buildings, where loadings may be subject to change. Buildings in earthquake zones may also benefit from additional toughness provided with external fabric/yarn reinforcement as a means of providing additional time for escape, for the occupants. Design/methodology/approach – The test compared four types of concrete beams with different reinforcement material compositions and each set consisted of three beams. The beams were: plain reinforced concrete without any external form of reinforcement (RC), plain unreinforced beams with a para aramid sheet (KF), plain unreinforced beams with para aramid strips of yarn attached longitudinally (KY) and plain reinforced concrete beams with sheet fabric (RCKF). All of the paraaramid material (fabric and yarn) was externally bonded to the samples, using a two part epoxy resin adhesive applied to a prepared surface. To determine the flexural strength and toughness a three point loading test was used to provide load and deflection data on the 12 (500mm x 100mm x 100 mm) concrete beams. Findings – An increase in flexural strength and toughness was observed when para-aramid was used in conjunction with steel reinforcement bar (re-bar). The para-aramid fabric and yarn produced similar results to the plain reinforced concrete beam in terms of flexural strength but not toughness. Originality/value – An advantage of using para-aramid as an external reinforcement, would be to utilise the large deflection the beam sustains under loading, whilst the fabric/yarn holds the beam together across the rupture plane. Although the testing did not prove that para-aramid would be a viable alternative to steel re-bar it did show that the material has the potential as an additional reinforcement that may be particularly useful where concrete structures are subject to large deformations or in need of repair.