Conventional concrete specification relies heavily on compressive strength, water-to-binder ratio, minimum cement content, and nominal cover, none of which directly measures the resistance of hardened concrete to chloride ingress, gas penetration, or capillary water absorption. This study reports a comparative experimental investigation of 41 concrete mixtures incorporating Ordinary Portland Cement (OPC), two sources of Ground Granulated Blast-furnace Slag (Slag), Class F fly ash, and Class C fly ash at replacement levels of 15–70%, together with binary and ternary combinations, across water-to-binder ratios of 0.35–0.50 and binder contents of 350–450 kg/m³. Compressive strength, surface electrical resistivity, rapid chloride penetration (RCPT) charge, oxygen permeability index (OPI), and water sorptivity were measured at 28 and 90 days. Mean compressive strength increased by 16.7% between 28 and 90 days, mean surface resistivity increased by 79.9%, and mean RCPT charge decreased by 27.9%. Surface resistivity and RCPT charge were strongly and inversely correlated at both ages (r = −0.704 at 28 days; r = −0.725 at 90 days), whereas compressive strength showed only a weak association with RCPT (r = −0.258) and an essentially negligible association with resistivity (r = +0.008) at 90 days. In a controlled comparison at w/b = 0.50 and 310 kg/m³ binder content, a 50% slag mixture achieved the most balanced performance, exceeding the OPC control in strength (59.23 vs. 54.62 MPa) while improving resistivity by 7.38×, RCPT resistance by 6.40×, and sorptivity resistance by 3.03×. A 50% Class F fly ash mixture achieved comparable or superior chloride-related resistance (RCPT resistance 7.17×) but at a substantial strength penalty (0.57× the OPC strength). The results demonstrate that compressive strength alone cannot rank the durability performance of SCM concretes, and that a multi-parameter, exposure-specific assessment framework combining resistivity, RCPT, OPI, and sorptivity is required for dependable material selection.

Keywords: Supplementary cementitious materials; Concrete durability; Surface electrical resistivity; Rapid chloride penetration; Oxygen permeability index; Water sorptivity; Correlation analysis.