Durability, scenario-based chloride-initiation assessment, and eco-efficiency of fine-grained concrete incorporating untreated saline sand and ground granulated blast-furnace slag

This study examines the use of untreated chloride-contaminated saline sand in coarse-aggregate-free fine-grained concrete with a ternary binder comprising Portland cement, fly ash (FA), and ground granulated blast-furnace slag (GGBS). Four mixtures were tested: a conventional concrete benchmark (S0) and saline-sand mixtures with 20%, 30%, or 40% GGBS replacement (S20, S30, and S40, respectively). The fine-grained mixtures reached 68.1–71.6 MPa at 180 days. Relative to S0, S30 showed 22.8% lower water absorption and S40 showed a 71.4% lower chloride migration coefficient; these were system-level differences. After 180 days in a 5% sodium sulfate (Na 2 SO 4 ) solution, S20–S40 retained 98.2–107.8% of their standard-cured strengths and exhibited expansion strains of 0.042–0.048%. The value above 100% for S30 was treated as an apparent response. Within S20–S40, increasing GGBS replacement reduced the chloride migration coefficient from 4.77 to 3.75 × 10 −12 m 2 /s and increased corrosion-induced cracking time from 35 to 63 days. This response does not isolate natural corrosion caused solely by saline-sand chlorides. Scenario-based modeling preserved the S20 < S30 < S40 ranking under standardized assumptions. S40 reduced embodied carbon dioxide (CO 2 ) emissions by 34.2%. S30 provided the most balanced profile, whereas S40 led the chloride-related and carbon-efficiency indicators.