Assessing the chloride-ingress performance of binary and ternary low-clinker concretes through electrical resistivity measurements

With increasing use of high levels of supplementary cementitious materials to reduce clinker content, a comprehensive understanding of hydration and microstructural development within the concrete cover zone is critical to durability and long-term performance. This paper examines the application of electrical property measurements as a simple, non-destructive methodology for monitoring these processes in low-clinker concretes incorporating binary and ternary blends of ground granulated blast-furnace slag (GGBS), fly ash (FA) and/or limestone powder (LP). Measurements were obtained at a depth of 50 mm from the exposed surface, from initial gauging, through setting and over an extended period approaching 500 days. All mixes exhibited continual increases in resistivity, indicating ongoing hydration and refinement of the pore network beyond conventional curing. At longer timescales, the FA concretes achieved the highest resistivity, while the GGBS mixes demonstrated intermediate and sustained increases, significantly higher than those of Portland cement concrete. LP contributed marginally, primarily through early-age physical effects. Ternary GGBS/FA blends displayed synergistic long-term benefits. To rank mix performance to chloride ingress, resistivity was combined with estimated pore-fluid resistivity to compute formation factors and instantaneous chloride diffusion coefficients. The results highlight the potential of electrical measurements as a practical methodology for durability classification, offering a practical pathway to performance-based assessment of low-clinker concretes.