Contribuição sobre o comportamento do concreto de altíssimo desempenho reforçado por fibras hibridizadas (HyUHPFRC)

Abstract

Ultra-high-performance fiber-reinforced Concrete (UHPFRC) has gained prominence in critical structural applications due to its superior mechanical properties. The hybridization of UHPFRC with steel and polyvinyl alcohol (PVA) fibers (HyUHPFRC) aims to optimize these properties by leveraging the synergistic effects of micromechanical resistance mechanisms. These mechanisms significantly influence the composite’s behavior. Therefore, this work contributes to the understanding and micromechanical analysis of hybrid fibers, incorporating phenomena such as the Pulley-friction effect and the Cook-Gordon effect into the tensile behavior of the composite while exploring their influence on mechanical properties and carbon dioxide (CO2) emissions. This study advances the micromechanical analysis of hybrid fibers, combining experimental investigations through microscopy and numerical simulations using the Finite Element Method (FEM). Additionally, a fracture analysis was conducted in conjunction with micromechanical studies, enabling the adjustment of the bond stress of PVA fibers. Hybridization significantly improved the mechanical properties of HyUHPFRC, achieving a 50% increase in tensile strength, an 8% increase in compressive strength, and an 87% increase in flexural strength compared to conventional UHPFRC. The material exhibited a gradual strain-hardening behavior, with fracture energy 10 times higher and pseudo-strain-hardening 30% greater. The partial replacement of steel fibers with PVA reduced CO2 emissions by 30% but impacted workability due to the hygroscopic characteristics of PVA fibers. The proposed constitutive law coupled with fracture analysis ensured better prediction of hybrid behavior, accurately adjusting the post-peak response of the samples. Thus, this work contributes to structural and materials engineering advancements, offering a sustainable and robust approach to modeling hybrid composites.