Spatial durability variations in RC members under gradient electrothermal curing: Insights from micropore characteristics

Electric activation curing (EAC) is promising for concrete construction in cold regions. Reinforcement disturbs the electrothermal fields within structural members, while its influences on curing effectiveness and durability are not well clarified. Previous studies mainly adopted unreinforced specimens, limiting the practical application of existing results. This work designs reinforced concrete beams with varied rebar arrangements to generate gradient electrothermal fields, investigating member curing effectiveness as well as key factors governing spatial durability. Results demonstrate that EAC significantly enhances impermeability, reducing water absorption, chloride migration, and carbonation depth by 13.8 %, 40.6 %, and 40.7 %, respectively, while maintaining compressive strength comparable to standard condition curing (SCC). The continuously varying and non-uniform electrothermal field within a same reinforced concrete member affects the concrete's compressive strength and impermeability; compressive strength differed by 6.6 %, while the water absorption and chloride ion migration differed by 6.4 % and 18.8 %, respectively. Microstructural analysis (MIP and X-CT) revealed that EAC optimizes the pore structure by increasing the volume of sub-20 nm pores and shifting the dominant factor for chloride resistance to the percolation fractal dimension. Grey relational analysis further identified scale-dependent key pore parameters governing durability. This work provides a crucial theoretical basis for applying EAC technology to full-scale reinforced concrete structures in cold environments.