Microstructural and mechanical assessment of sulfate-resisting cement concrete over portland cement incorporating sea water and sea sand

The use of seawater and sea sand in concrete is becoming more prominent, particularly for marine structures, as a solution to the shortage of freshwater and natural aggregates. This research evaluates the durability of concrete made with seawater, fly ash, and recycled sea aggregates. Various techniques, including SEM-EDS, FTIR, M-Ct, and TG/DTA, were employed to analyze the microstructure of this concrete. Mechanical properties were assessed by measuring the compressive strength after 28 days. The findings indicated that higher proportions of sea-based materials increased porosity, while FTIR showed the absence of portlandite due to the use of sulfate-resisting cement. SEM-EDS confirmed XRD results quantitatively. Compressive strength improved with up to 50 % replacement of the original composition. The study demonstrates that incorporating seawater enhances the pozzolanic properties of cement, increasing the formation of Calcium-Silicate-Hydrate (C-S-H) gel, which contributes to a dense microstructure and good mechanical strength comparable to conventional freshwater concrete. These results support the use of seawater, sea sand, and recycled aggregates as sustainable alternatives, balancing structural performance and environmental sustainability in construction materials.