Abstract
Employing a long-term chloride salt wet-dry cycling test method, this study investigates the influence of different steel fiber volume fractions on the chloride ion transport properties of UHPC, and analyzes the temporal evolution of the apparent chloride diffusion coefficient and surface chloride concentration. The results demonstrate that: (1) after 180 days of wet-dry cycling, a convection zone emerges at a depth of 2 mm in UHPC, and the internal chloride ion concentration distribution conforms to Fick's second law; (2) the incorporation of steel fibers does not affect the formation of the convection zone; during the early exposure period, the apparent diffusion coefficient of UHPC increases with increasing steel fiber volume fraction, while gradually decreasing with increasing concrete age; (3) the surface chloride concentration tends to stabilize over time, with its development following an exponential model.
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Preamble
Effect of Steel Fibers on Chloride Penetration Resistance of UHPC under Wet-Dry Cycles
Li Cheng
China Railway 16th Bureau Group Road and Bridge Engineering Co., Ltd., Beijing 101500, China
Abstract
This study investigates the effect of steel fiber volume fraction on chloride transport properties in Ultra-High Performance Concrete (UHPC) through long-term wet-dry cycling tests in chloride solution. The time-dependent variations of the apparent chloride diffusion coefficient and surface chloride concentration are analyzed. The results reveal that: (1) after 180 days of wet-dry cycling, a convection zone forms at a depth of 2 mm in UHPC, and the internal chloride concentration distribution conforms to Fick's second law; (2) steel fiber incorporation does not influence the formation of the convection zone; during the early exposure period, the apparent diffusion coefficient of UHPC increases with increasing steel fiber volume fraction but gradually decreases with age; and (3) the surface chloride concentration tends to stabilize over time, following an exponential development model.
Keywords: Ultra-High Performance Concrete; steel fiber; chloride transport; apparent chloride diffusion coefficient