Carbon Fiber–Garnet Sand Reinforced Multifunctional Electrically Conductive Concrete for Supercapacitive Energy Storage

This study reports the development of an electrically conductive concrete (ECC) prepared by incorporating 2 vol.% carbon fibers (CF) and iron-rich almandine garnet sand into a Portland cement matrix, followed by surface coating with activated carbon to enable electrochemical energy storage through an electrode layer. The optimized ECC formulation exhibited significantly enhanced electrical and mechanical performance, achieving a low electrical resistivity of 15 Ω·cm after 28 days of curing, along with compressive and flexural strengths of 39 and 13.4 MPa, representing approximately 50% and 35%, improvements respectively over conventional mortar. FE-SEM and elemental analyses confirmed the effective infusion and dispersion of carbon fibers within the cementitious matrix, establishing a continuous conductive network. When employed as a conductive substrate for supercapacitor electrodes and evaluated in a hydroquinone/Na₂SO₄ aqueous electrolyte, the ECC-based device delivered a high specific capacity of 217 C g⁻¹, an energy density of 17.36 Wh kg⁻¹, and retained 78% of its initial capacity after 5000 charge–discharge cycles. These results demonstrate the potential of carbon-fiber-reinforced ECC as a multifunctional material that enables the integration of structural integrity with electrochemical energy storage, offering a promising pathway toward intelligent and sustainable infrastructure systems.