Experimental Evaluation of Corrosion-Induced Strength Loss in RC Beams under H₂SO₄ Exposure

Abstract

Reinforced concrete (RC) structures in wastewater treatment plants, industrial facilities, and sewer systems are frequently exposed to aggressive acidic environments, particularly sulphuric acid (H₂SO₄). Such exposure accelerates reinforcement corrosion and compromises structural integrity, creating significant durability challenges for civil infrastructure. While chloride-induced corrosion and carbonation have been widely studied, limited attention has been given to systematic quantification of mechanical deterioration in RC beams subjected specifically to sulphuric acid immersion. This gap restricts predictive modeling and the development of effective mitigation strategies. This study investigates corrosion-induced strength degradation in RC beams exposed to sulphuric acid. The objective was to quantify mechanical deterioration over time and evaluate the influence of acid exposure on surface hardness and flexural performance. Beam specimens were cast using Portland cement concrete reinforced with deformed steel bars, cured for 28 days, and immersed in a 0.4 M H₂SO₄ solution for 7, 14, 28, and 56 days. Control specimens were submerged in water under identical conditions. Mechanical characterization involved Brinell Hardness Number (BHN) testing to assess surface integrity and center-point bending tests to evaluate flexural strength. Load-deflection behavior and residual strength were statistically analyzed to identify degradation patterns. Results revealed severe deterioration under acid exposure. Specimens with initial BHN of 600 dropped to 39 after 56 days, compared to 683 in controls. Similarly, samples starting at BHN 630 dropped to 55, while controls reached 700, representing hardness reductions exceeding 90%. Flexural strength degradation followed a logarithmic trend, with acid-exposed beams at 7 days reaching ~10.5 kN peak loads, while 56-day specimens fell significantly lower. Benchmarking against chloride-induced corrosion studies, which report 30–50% strength loss, highlights that sulphuric acid exposure produces far more severe deterioration. These findings underscore the urgent need for protective measures and predictive models tailored to acid-rich environments.