This study evaluates the chemical aggressiveness of sulfate-bearing soils and its implications for concrete durability in the 12 de Marzo District, Portoviejo, Ecuador. Fourteen soil samples collected between May and June 2025 were analyzed using standardized laboratory procedures based on ASTM International standards (ASTM D2487; ASTM C1580-20), complemented by GIS-based spatial analysis. Sulfate concentrations were classified according to American Concrete Institute (ACI 201.2R-16), identifying moderate (S1) and severe (S2) exposure levels in several zones, with values exceeding 1,000 ppm. Fine-grained soils, particularly ML and MH, exhibited higher sulfate retention capacity, influenced by environmental and anthropogenic factors such as wastewater infiltration and proximity to surface water bodies. The study is limited to soil chemical characterization and does not include experimental evaluation of concrete performance; therefore, recommendations are based on exposure classification criteria. The findings support durability-oriented design and urban planning in chemically aggressive environments.