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In order to investigate the effects of steel fiber, polyvinyl alcohol (PVA) fiber and mineral powder contnet on permeability resistance of steel-PVA hybrid fiber high performance concrete (HFHPC). The orthogonal experiment was designed to conduct the permeability resistance test of steel-PVA HFHPC, and the test results were analyzed through range analysis, variance analysis and regression analysis. The results show that the influence degree on the impermeability of HFHPC is steel fiber, mineral powder and PVA fiber from high to low. In the range of test level, the optimal horizontal combination of impermeability of concrete specimens is as follows: steel fiber volume fraction of 1.0%, PVA fiber volume fraction of 0.7% and slag powder mass replacement rate 20% . When the steel fiber volume fraction exceeds 1.0%, the impermeability of HFHPC decreases slightly, but it is still higher than that of standard plain concrete. Finally, multiple regression analysis is used to establish the prediction model of HFHPC permeability and steel fiber, PVA fiber and mineral powder. [ABSTRACT FROM AUTHOR]

Hybrid Fiber High Performance Concrete (HFHPC) utilizes the synergistic effects of macro and micro fibers at different stages, which can effectively improve its mechanical properties, fracture toughness, ductility, and impact resistance after high temperature. The bonding between steel bars and hybrid concrete is a fundamental prerequisite for ensuring that these two materials with completely different mechanical properties work together. In order to study on bond-slip performance and damage evolution mechanism of deformed reinforcing bar embedded in steel-polyvinyl-alcohol (S-PVA) hybrid fiber high performance concrete (HFHPC) after high temperature, a total of 75 specimens were designed and manufactured by selecting volume fraction of steel fiber and PVA fiber and dosing of slag powder as the orthogonal test factors, and the central pull-out test were completed after exposure to room temperature, 200℃, 400℃, 600℃, and 800℃. The experimental results indicate that the bonding failure mode of HFHPC specimens all showed steel bar pull-out failure after high temperature, and the bond stress-slip curve can be divided into 4 stages: elastic rise stage, nonlinear rise stage, plastic degradation stage, and residual stage. As the temperature increases, the bonding strength of HFHPC specimens gradually decreases and the peak slip gradually increases. The addition of hybrid fibers can significantly improve the bonding ductility and energy dissipation capacity of deformed reinforcing bar embedded in S-PVA HFHPC after high temperature. When the temperature is below 200℃, the bonding strength damage rate of S-PVA HFHPC specimens is relatively slow; when the temperature exceeds 200℃, the bonding strength damage rate of S-PVA HFHPC specimens increases. • The effects of steel-polyvinyl-alcohol hybrid fibers on bond-slip performance after high temperature were investigated. • Improvements in the bonding failure mode, bond strength, slip, energy consumption and ductility after high temperature were observed. • Damage evolution mechanism of deformed reinforcing bar embedded in steel polyvinyl-alcohol hybrid fiber high performance concrete after -high temperature were developed. [ABSTRACT FROM AUTHOR]

• The mechanical property tests and test of GFRP reinforced hybrid fibre concrete short columns subjected to eccentric compression were conducted. • The cooperative effect of the GFRP reinforcement and the steel-PVA hybrid fibre concrete with different fibre ratios under eccentric loading was explored. • The addition of fibres can effectively prevent the crack generation and development and improve the bonding property between reinforcement bars and concrete. • The equation for the calculation of the ultimate compressive capacity of partial sections of eccentric columns is proposed. This paper presents the results of an experimental study carried out on the GFRP reinforced hybrid fibre concrete short columns subjected to eccentric compression. In this study, hybrid fiber-reinforced concrete was prepared in different volume ratios of hybrid fibers and the cooperative effect of the GFRP reinforcement and the steel-PVA hybrid fibre concrete with different fibre ratios under eccentric loading was explored. 10 GFRP reinforced hybrid fibre concrete short columns and 2 plain reinforced concrete short columns were tested to investigated their eccentric compressive properties. The tests results are presented in terms of failure modes, longitudinal reinforcement strain, concrete compressive strain and compressive load capacity of GFRP reinforced hybrid fibre concrete eccentrically compressed short columns. The results show that the concrete on the compressed side was crushed when the specimen under both the initial eccentricity of 50 mm and 100 mm the reinforcement were pulled on the tension side of specimen under a larger initial eccentricity of 100 mm. The addition of fibres can effectively prevent the crack generation and development and improve the bonding property between reinforcement and concrete. Besides, the addition of steel fibre contributes a better performance on the ultimate compressive capacity of specimen under a lager initial eccentricity with an optimal ratio of steel fibre at 1.4 %. PVA fibre effectively improve the ductility of the concrete, so that the hybrid fibre concrete elements remain relatively its integrity after failure. Finally, considering the effect of GFRP reinforcement and different ratios of steel fibre and PVA fibre on the compressive capacity of short concrete columns, the equation for the calculation of the ultimate compressive capacity of partial sections of eccentric columns is proposed, and a good agreement was observed between the tested and calculated value. [ABSTRACT FROM AUTHOR]