Ultra-high-performance concrete (UHPC) formulated with alternative binders represents a promising pathway for reducing carbon emissions while enabling multifunctional material performance. This study investigates the mechanical and electrical evolution of two systems: a traditional Portland cement-based UHPC (REF) and a geopolymer counterpart (GEO) where cement is fully replaced by ground granulated blast furnace slag (GGBS) and silica fume. By evaluating both mixes with and without steel fibers, the research assesses how binder chemistry interacts with conductive pathways to influence strength, resistivity, and impedance. Mechanical testing revealed comparable 28-day compressive strengths for the reference and geopolymer mixes (123 MPa and 120 MPa, respectively), which increased to 139 MPa and 130 MPa upon fiber incorporation. Electrical characterization showed that the geopolymer binder significantly enhances conductivity; resistivity values dropped from 9645 Ω·m in the reference mix to 925 Ω·m in the geopolymer and further to 76 Ω·m with fiber reinforcement. Impedance spectroscopy supported these results, as the GEO mixes displayed smaller Nyquist arcs compared to the REF system, indicating greater ionic mobility associated with pore solution chemistry and the GGBS-rich gel structure. Ultimately, this study demonstrates that geopolymer UHPC matches the mechanical integrity of Portland-based systems while offering superior electrical conductivity, making it a strong candidate for low-carbon, self-sensing infrastructure.
Sleiman et al. (Tue,) studied this question.