CHLORIDE DIFFUSION RATE IN LOADED FLY ASH CONCRETE USING STEADY-STATE MIGRATION TEST

Abstract

Chloride-induced corrosion is a major durability concern for concrete structures in marine environments, particularly under mechanical loading, as the resulting micro-cracking and cracking can accelerate chloride ingress, allowing these corrosive ions to reach the steel reinforcement more easily and compromise the structure's integrity. This study investigates the combined effect of mechanical pre-loading and fly ash replacement (0%, 20%, 30%, and 40%) on chloride diffusion in high-strength concrete. Sixteen concrete discs were tested using the NT Build 355 steady-state migration method for durations of 7 and 14 days. Before testing, a load of up to 2,000 kilograms was applied to eight specimens, while the remaining eight were left unloaded. The chloride diffusion coefficient was calculated using the Nernst-Planck equation. The results demonstrated that increasing fly ash content consistently reduced chloride ingress, with a maximum reduction of 79.8% observed in specimens with 40% fly ash under pre-loading conditions. These reductions were repeatable across both durations and fly ash percentages, with notably greater performance observed at 30% and 40% replacement compared to 20%. Replacing cement with 30–40% fly ash significantly enhances the durability and extends the service life of concrete structures in marine environments, even when subjected to pre-loading. Additionally, this approach contributes to sustainability by reducing cement consumption, which in turn lowers carbon dioxide emissions.