Improving concrete structures with engineered cementitious composites and kevlar sheets: an affordable retrofitting solution for earthquake resistance

Abstract This paper outlines experimental and analytical studies focused on strengthened concrete specimens using Engineered Cementitious Composites and use of Kevlar sheets is highlighted as one of the most effective techniques for achieving the desired structural reinforcement and extending the lifespan of structures. The research examines the mechanical properties of retrofitted concrete and material characterizations of ECC such as Scanning Electron Microscopy and Energy dispersive x-ray analyses were also carried out to corroborate the durability properties of ECC and Kevlar-wrapped specimens, specifically assessing compressive, tensile, and flexural strength. In this study, fiber-reinforced cementitious materials featuring a 2% volume fraction of hybrid fibers comprising hooked-end steel and polyvinyl alcohol fibers were employed to strengthen the concrete structure. This additional layer enhances tensile strength and aids in crack management, necessitating proper curing to ensure strength gain over a specified duration. Kevlar fabric sheets are carefully applied to the ECC surface using resin to create a strong bond between the Kevlar and the underlying material, resulting in a durable retrofitted structure. Preliminary experimental data supported numerical modelling of the specimens using finite element analysis. The numerical results regarding the retrofitted strength of hardened concrete were compared with experimental outcomes. The findings showed that the maximum load of the strengthened samples increased by 6.5%. Additionally, the retrofitted strength prior to complete failure rose by 10.6%. In conclusion, the integration of hybrid fibers for reinforcement and Kevlar for retrofitting proves to be a cost-effective and straightforward approach.