To address the lack of reliable curing strategies for seawater sea-sand concrete (SSC) in extremely cold marine regions, this study proposes an ohmic-heating (OH) curing approach that enables self-generated internal heating through a percolation-based conductive network. This energy-efficient method simultaneously promotes rapid hydration, microstructural stabilization, and long-term durability. A percolation-controlled conductive network was achieved by incorporating 1.25 vol% carbon fibers (CFs), reducing electrical resistivity from 102.16 Ω·cm to 52.01 Ω·cm while maintaining a slump of 16.1 cm. The resulting internal temperature rise (65 ± 2 °C) accelerated hydration and produced a 2-day compressive strength of 65 MPa. Mercury intrusion porosimetry revealed that OH curing refined the pore structure, with total porosity decreasing to 13.1 % and the fine-pore (< 50 nm) fraction increasing to 0.52. The ohmic-heating followed by freeze treatment (OHF) specimens exhibited superior microstructural stability after 300 freeze–thaw cycles. Chloride-exposure tests showed minimal penetration (≈ 3 mm) and over 90 % strength retention after 90 days in OH-cured samples. Accelerated carbonation tests confirmed the lowest full and partial carbonation depths (1.2 mm and 16.9 mm, respectively), attributed to CaCO3 precipitation within microcracks and pores observed by SEM. This study reveals a self-regulated pore stabilization and crystallization-filling mechanism, wherein ohmic heating promotes secondary C–S–H and AFm phase formation that dynamically heals microvoids and stabilizes the pore network. The findings establish OH curing as a multifunctional, low-energy, and durable curing strategy for SSC, providing a mechanistic foundation for sustainable construction in cold marine environments.