Fiber-reinforced polymer (FRP) systems face siginificant challenges from limited thermal performance and poor compatibility with cementitious substrates, hindering their wide utility in reinforcing and retrofitting structures. To address these limitations, a novel alternative reinforcing system, called mineral-impregnated carbon fibers (MCFs), has recently introduced, combining high-performance carbon fiber yarns with inorganic matrices. This approach delivers evidently enhanced resistance to high temperatures, bond with concrete, cost-effectiveness and technological flexibility in applications. By activating added electrothermal functionality beyond primary structural benefits, the present paper focuses on development and testing of the designed MCF system as efficient Joule heater for rapid concrete curing and maintenance of civil infrastructure. MCFs were fabricated using automated pultrusion and geopolymer impregnation techniques, achieving extremely low electrical resistivity (8.47 Ω·μm) and uniform heat distribution under applied DC voltages. Penetration tests confirmed that electrothermal activation at defined curing temperatures of 50 °C and 75 °C enabled very rapid setting and exceptional early strength gain in geopolymer concrete (GPC) prototypes reinforced with MCF within 160 min only, in contrast to air-cured control composites, which remained unset. FT-IR spectroscopy demonstrates advanced geopolymerization via the presented electrothermal activation, leading to improved early strength development. The exceptional curing efficiencies achieved via the MCF system with low energy input offer a cost-effective, energy-efficient, and highly flexible solution for accelerated curing, rapid infrastructure recovery, and improved durability in modern construction.