Electrical and mechanical characteristics of CaO-activated cementless ultra-high performance concrete (UHPC) incorporating steel slag aggregates

This study presents a sustainable and intelligent alternative to conventional cement-based ultra-high performance concrete (UHPC) by developing a CaO-activated GGBFS cementless UHPC incorporating rapid-cooled electric arc furnace oxidizing slag (REOS) as a replacement for natural aggregates. As an industrial byproduct, REOS enhances mechanical performance while promoting electrical conductivity, forming efficient conductive networks within the matrix. These pathways enable self-sensing capabilities, allowing the material to detect stress and strain without external sensors. The experimental results showed that REOS improved fluidity (up to 235 mm) and maintained high compressive strength (exceeding 200 MPa). Additionally, it was found that REOS enhanced tensile properties, achieving tensile strength exceeding 21 MPa and maximum strain capacity of 0.72 %, particularly when combined with 0.3 % carbon fiber. The incorporation of carbon fiber significantly reduced electrical resistivity compared to the composite without carbon fiber. Furthermore, a life cycle assessment (LCA) demonstrated the environmental benefits of REOS, showing approximately 53 % lower carbon dioxide (CO₂) emissions per unit compressive strength compared to traditional UHPC. This research highlights the multifunctionality of REOS in improving both performance and sustainability, offering valuable insights into the development of next-generation UHPC that integrates advanced sensing capabilities and aligns with circular economy principles.