REDUCING THE EFFECTS OF SALT WATER ON CONCRETE USING FLY ASH AS A PARTIAL REPLACEMENT FOR CEMENT

Concrete deterioration due to exposure to aggressive environments, particularly saltwater, remains a major durability challenge in coastal and marine construction. The use of supplementary cementitious materials such as fly ash has gained attention for its potential to improve the long-term performance and sustainability of concrete structures. This study investigates the effect of fly ash on the strength and durability of saltwater concrete, focusing on optimizing its percentage replacement for structural applications. The primary aim of the research was to evaluate how partial replacement of Ordinary Portland Cement (OPC) with fly ash affects the compressive strength and resistance to saltwater attack. Experimental tests were conducted using mix ratios with 0%, 10%, 15%, 20%, and 25% fly ash as partial cement replacements. Concrete cubes were cast, cured in saltwater, and tested at 7, 14, 21, and 28 days. Workability, visual inspection, and compressive strength were measured in accordance with ASTM and BS standards. Results revealed that the compressive strength increased with curing age for all mixes, but declined slightly as fly ash content increased beyond 15%. The optimum performance occurred at 10–15% fly ash, producing 28-day compressive strengths ranging from 25.46 N/mm² to 27.42 N/mm², compared to 22.95 N/mm² at 20% and 20.09 N/mm² at 25% replacement. Visual assessments indicated improved surface integrity and reduced efflorescence for moderate fly ash mixes, confirming enhanced durability in saline conditions. The study concludes that 10–15% fly ash replacement provides the best balance between strength and durability for saltwater concrete. It is therefore recommended for marine and coastal structures to enhance performance, reduce cement consumption, and promote environmental sustainability.