TY  - EJOU
AU  - Li, Yu 
AU  - Wang, Xinyi 
AU  - Yang, Deqiang 

TI  - Electrochemical Characteristics of Steel Corrosion in Nano-SiO<sub><b>2</b></sub> Modified Recycled Concrete under Dry-Wet Cycles
T2  - Structural Durability \& Health Monitoring

PY  - 
VL  - 
IS  - 
SN  - 1930-2991

AB  - To address the insufficient durability of recycled aggregate concrete (RAC) applied in the inland river bridge splash zone under low-chloride salt wet-dry cycling, this study systematically investigated the electrochemical corrosion characteristics of HRB400 steel reinforcement in nano-SiO<sub>2</sub> modified RAC. With recycled coarse aggregate replacement ratios of 0% and 50% and nano-SiO<sub>2</sub> dosages of 0%, 3%, and 6% as key variables, 300 accelerated dry-wet cycle tests were conducted in accordance with GB/T 50082-2009. Open circuit potential (OCP), linear polarization, and electrochemical impedance spectroscopy (EIS) were adopted to characterize the corrosion evolution of steel bars, combined with porosity analysis to clarify the modification mechanism. The results indicated that the passive film of steel in unmodified RAC (C0-R50) failed and initiated active corrosion at approximately 150 dry-wet cycles; 50% RAC incorporation increased the total porosity of concrete from 14.2% to 16.8%, accelerated the diffusion of oxygen and moisture, and significantly elevated the corrosion current density throughout the cycling process. NS modification effectively retarded carbonation-induced depassivation via pozzolanic reaction and micro-filling effect: after 300 cycles, the |Z| of the 3% NS natural aggregate group (C3-R0) reached 1380 Ω⋅cm<sup>2</sup>, while that of the 6% NS group (C6-R0) maintained 2087.4 Ω⋅cm<sup>2</sup>, both far exceeding the control group C0-R0 (544.5 Ω⋅cm<sup>2</sup>). The optimal anti-corrosion performance was achieved by 6% NS dosage, which reduced the final <i>I</i><sub>corr</sub> of C6-R0 by 91% compared with C0-R0, lowered the porosity of 50% RAC to 13.6%, and maintained a high charge transfer resistance (<i>R</i><sub>ct</sub>) of 10,046.0 Ω⋅cm<sup>2</sup> after 300 cycles. Even in the 50% RAC system, 6% NS retained a high |Z| of 2191.1 Ω⋅cm<sup>2</sup> at 150 cycles, effectively compensating for the interfacial defects of recycled aggregate. Notably, the C3-R0 group presented a localized impedance peak at 200 cycles, attributed to the temporary accumulation of dense hydration/corrosion products. This study provides quantitative experimental data and a microscopic mechanism support for the engineering application of high-dosage nano-SiO<sub>2</sub> modified recycled concrete in the splash zone of inland river bridges.
KW  - Recycled concrete; nano-SiO<sub>2</sub>; dry-wet cycles; steel corrosion; electrochemical characteristics

DO  - 10.32604/sdhm.2026.084012