Effects of Acid Deposition on Portland Cement Concrete

Cyclic Polarization of Corrugated Austenitic Stainless Steel Rebars in Acid Rain: Effect of Fly Ash, pH and Steel Type

“…The selection of the aforementioned pH values was based on the following rationale: as sulfuric acid simultaneously penetrates and chemically reacts with concrete [52], acid rain can directly attack the reinforcement only when the concrete cover is cracked (conversely, it is well-documented in the literature that chloride diffuses through concrete porosity to the rebar surface without any strong and harmful interactions with the cementitious binder [52]). It is also taken into account that: (a) an alkaline solution of saturated Ca(OH) 2 (i.e., 1.8 g of Ca(OH) 2 per L of H 2 O, pH ≈ 12.5) simulates the solution remaining in the pores and capillary voids of the concrete after the hydration process [53]; (b) acid attacks to the cement paste involve a continuous travel of Ca(OH) 2 from the interior of the structure to the surface, resulting in an unsaturated concrete pore solution [11]; (c) in high sulfate and low pH environments, the corrosion of the reinforcing steel is the dominant degradation mechanism of a concrete structure [12]. Therefore, it is herein postulated that the slightly alkaline aqueous solution of pH = 7.5-7.9 may simulate a cracked concrete cover that has directly exposed the steel reinforcement to acid rain in compatibility with Fan et al [54].…”

“…Corrosion due to acid rain attack has gained rapidly increasing significance owing to recent acute urban and industrial activities [9,10]. An acidity of pH = 3.0-6.5 is detrimental to concrete of high quality [11,12]. Deterioration has been observed even in high performance concrete at pH values lower than 6.5 and sulfate concentrations greater than 500 ppm [12].…”