Impact resistance and flexural behavior of U-shaped concrete specimen retrofitted with polyurethane grout

Normal concrete-polyurethane grout (NC-PUG) composite U-shaped and beam specimens were developed in this study to evaluate the capability and efficacy of PU grouting material prepared from mixing bio-based polyurethane (PU) and quartz sand as a coating material. The composite specimens were subjected to dynamic and flexural loads using U-shaped drop-weight impact test (USDWIT) and three-point bending test, respectively. Various PUG overlaid thicknesses and configurations were adopted to improve the impact and flexural behavior of the concrete. Weibull distribution analysis was performed on the USDWIT result. The result indicated that the reference NC-PUG beam exhibited the highest load-carrying capacity of 18.26 kN and the lowest ultimate deflection of 0.52 mm compared to the composite NC-PUG specimens. While, the NC beam retrofitted with a 10 mm thickness overlaid at the top surface (NC-PUGT10) revealed a reduced ultimate load-carrying capacity compared to the reference NC-PUG specimen. The impact performance of the composite U-shaped NC-PUG specimen have remarkably improved due to the influence of PU grouting materials overlaid, with a higher ductility index, which tends to change the brittle nature of concrete to a ductile state. The energy absorption capacity at the failure stage of the NC-PUGT5 is 16 times that of the reference U-shaped NC-PUG specimen. The NC-PUGTB5 and NC-PUGT10 revealed impact strength, which is 52.28 times and 68.1 times more than the reference specimens, respectively. Reliability analysis indicated that about 80% of the U-shaped NC-PUG specimen can withstand 63 impact times at the failure stage. The finding showed that retrofitting concrete structures with PUG material is a promising and sustainable method to protect the concrete structure against dynamic loads