Thermal and Mechanical Performance of Steel Slag and Graphite Modified Concrete with a Comparative Engineering Cost Assessment

The heat generated by electrical cables during operation dissipates through the duct and surrounding encasement concrete into the adjacent soil. Consequently, the thermal conductivity of the encasement concrete is critical for the overall heat dissipation efficiency and thermal stability of the cable system. To address this, a high-thermal-conductivity concrete was developed by incorporating steel slag powder, graphite powder, and graphite particles. This study systematically investigated the effects of mineral admixture content, graphite powder dosage, and the replacement ratio of conductive aggregates on the thermal conductivity, mechanical properties, and workability of the concrete. Additionally, the economic performance was evaluated against conventional C25 concrete using value engineering methodology. The results demonstrate that the proposed concrete exhibited significantly improved thermal performance compared to ordinary concrete. Notably, with a 10% replacement of aggregates by graphite particles, the 28-day thermal conductivity increased by 106.16% relative to the control mix. Simultaneously, the compressive strength reached 25.1 MPa, ensuring sufficient mechanical integrity. Furthermore, the value coefficient of the developed concrete was 18.31% higher than that of conventional C25 concrete. These findings highlight the material’s potential in power engineering and energy-efficient construction, providing a valuable reference for material design in these fields.