Durability challenges of concrete structures in chemically aggressive riverine zones contaminated by textile discharge: a brief review
Md Faiyaz Shahriar, T.S. Kamal, Rizwanur Rahman
Abstract
Abstract In Bangladesh, the rivers surrounding capital Dhaka, Shitalakkha, Buriganga and Turag are severely contaminated by the direct discharge of untreated textile wastewater from surrounding industrial zones. Many reinforced concrete (RCC) structures such as bridges, culverts, embankments are situated along these polluted waterways and are continuously exposed to chemically aggressive effluents. Textile wastewater contains high concentrations of chlorides, sulfates, alkalis, dyes, surfactants, heavy metals, and organic compounds, with extreme pH levels ranging from strongly alkaline to strongly acidic (pH 2.9–13) during dyeing processes. Biochemical Oxygen Demand (BOD) levels reach critical values of 174 mg/L in Buriganga and 165 mg/L in Turag, far exceeding the 6 mg/L permissible limit. Sulfate ions induce ettringite and gypsum formation, causing expansion and strength losses of 15–30% after 12 months of exposure. Organic compounds retard cement hydration, reducing early strength by 5–15% and increasing water absorption by 10–20%, while facilitating microbial growth that creates acidic microenvironments. Chlorides accelerate reinforcement corrosion with 24–25% increased corrosion rates, reaching critical thresholds at around 1% chloride by weight of cement. High alkalinity triggers alkali-silica reaction in reactive aggregates, causing gel expansion of 200–300% and strength reductions of 15–20%. Iron oxides increase porosity and reduce compressive strength by up to 40% while nitrogenous organic compounds cause 20–30% strength loss and triple rebar corrosion rates to 0.3–0.5 µA/cm². These combined effects create highly porous concrete microstructures with enhanced carbonation depth, accelerated deterioration mechanisms, and significantly compromised structural integrity. Exposure to textile wastewater in polluted river zones causes synergistic chemical degradation that critically undermines the long-term durability of concrete infrastructure through multiple simultaneous attack mechanisms.