Mock-up pragmatic study on the impact performance of self-compacting concrete incorporating sea sand

Self-Compacting Concrete (SCC) allows for the use of non-desalted sea sand as a fine aggregate, but the durability of triple mix SCC with partial sea sand replacement remains unclear. To optimize binder and fine aggregate replacements, tests for consistency, setting times, soundness, compressive strength, and Ultrasonic Pulse Velocity were performed. Six SCC variations, incorporating 30% Class F Fly Ash (FA), 5% Ground Granulated Blast Furnace Slag (GGBS), and various fine aggregate combinations, were evaluated for their fresh, mechanical, microstructural, and durability properties. Results demonstrated that SCC with 50% sea sand and 50% manufactured sand achieved superior 90th day compressive strength. This improvement was attributed to accelerated cement setting and enhanced FA reactivity, leading to better hydration products. Microstructural analysis revealed more hydration products and fewer pores in specimens with 50% sea sand, due to the disconnected pore structure from Friedel’s salt formation. Chloride binding in concrete involves both chemical and physical mechanisms. Chemical binding is related to Friedel’s salt, while physical binding depends on Calcium-Silicate-Hydrate (C-S-H) content. Dense C-S-H formation from sea sand, confirmed by Scanning Electron Microscope (SEM) images, results in greater chloride binding. Additionally, aluminum oxide in FA and GGBS enhances chemical binding by forming Friedel’s salt.