Electrical durability tests for geopolymer concrete: assumptions, inconsistencies, and validation against chloride transport

Geopolymer concrete (GPC) is increasingly recognised as a low-carbon alternative to ordinary Portland cement (OPC), but its wider adoption depends on multiple factors, including mix design robustness, scalability, standards development, economic competitiveness, and long-term durability, particularly resistance to chloride-induced corrosion. Rapid electrical tests, including the Rapid Chloride Permeability Test (RCPT), Rapid Chloride Migration Test (RCMT), and resistivity measurements, are widely used to assess chloride transport resistance; however, their applicability to GPC remains uncertain. Conflicting results are frequently reported, arising from both the use of OPC-based interpretation frameworks for alkali-activated systems and variations in GPC mix design. This review critically evaluates the validity of electrical tests for GPC by examining underlying assumptions, material chemistry, and validation against diffusion-based measurements. It demonstrates that OPC-based interpretation frameworks cannot be applied directly to GPC because the electrical response may be strongly influenced by pore-solution chemistry. Evidence also suggests that OPC-based assumptions may be unreliable in GPC, as higher pore-solution ionic concentration and/or higher porosity do not always directly correspond to higher conductivity or lower resistivity. RCPT is particularly problematic in high-fly-ash systems, where premature termination may invalidate results under certain activator and curing regimes, yet it remains widely used. RCMT results can also diverge from natural diffusion behaviour. These limitations highlight the need for GPC-specific calibration and mechanistic interpretation grounded in chemistry. As a result, validation against diffusion-based measurements is required before electrical indices are used as proxies for chloride transport resistance. Although a few RCPT-specific validation approaches have recently been reported for fly ash- and GGBS-based systems, their applicability to other precursor chemistries remains to be further validated. The development of unified, chemistry-informed durability classification frameworks for GPC is therefore needed to enable reliable interpretation of electrical test results across diverse geopolymer systems.