Thermal and electrical performance of ultra-high electrically conductive cementless composite (UH-ECCC) incorporating steel slag

Abstract

This study explores the thermal and electrical performance of ultra-high electrically conductive cementless composite (UH-ECCC) incorporating rapid-cooled electric arc furnace oxidizing slag (REOS) as a sustainable and multifunctional fine aggregate for smart infrastructure applications such as pavement de-icing and self-heating curing. REOS, an iron-rich steelmaking byproduct, was used to partially or fully replace silica sand, aiming to enhance workability, electrical conductivity, and self-heating capability without compromising mechanical strength. The spherical morphology and high Fe2O3 content of REOS contributed to improved flowability through a ballbearing effect and facilitated the formation of continuous conductive pathways within the matrix. Experimental results showed that the compressive strength remained above 80 MPa for all mixtures, while flowability increased with increasing REOS content. Electrical conductivity increased by approximately 200%, from 1.31 S/m in the control mix with 100% silica sand to 3.93 S/m in the mixture where silica sand was fully replaced with REOS. Under 9 V direct current (DC) loading, the peak surface temperature of the UH-ECCC reached approximately 108 degrees C with an initial heating rate of 1.26 degrees C/min. Infrared imaging and thermal surface mapping of the UHECCC confirmed that the incorporation of REOS facilitated a highly uniform and intense heat distribution, suggesting the presence of efficient and well-connected internal conductive pathways. Furthermore, the composites maintained consistent electrical stability under repeated heating-cooling cycles, showing minimal variation in resistance. These findings demonstrate the potential of REOS as a sustainable alternative to natural aggregates for developing cementless concrete systems with self-heating functionality, as it synergistically interacts with CNTs and steel fibers to enhance conductivity and thermal performance without compromising flowability, thereby reinforcing its multifunctional advantages for smart infrastructure applications.