Deterioration Mechanism of Concrete Subjected to Acid Rain Attack—An Experimental and Modeling Approach

Abstract

The experimental and modeling approaches were taken to study the deterioration mechanism of concrete under acid rain attack. Concrete specimens were prepared and exposed to the simulated acid rain environment. The neutralization depth of concrete was measured, and the mineralogical composition and microstructure of concrete were analyzed using X-ray diffraction (XRD) and scanning electron microscope (SEM). The experimental results show that the degradation of concrete increases with the corrosion time and the decrease in pH value of acidic solution from 3.5 to 1.5. Concrete was corroded by H⁺ and SO₄²⁻ in acid rain, producing gypsum and leading to the neutralization of concrete. The acid rain exposure also resulted in the decomposition of hydration products of cement, such as C-S-H and ettringite, forming the main corrosion products of gypsum and SiO₂·nH₂O. Based on the second Fick diffusion law, a model was developed to describe the deterioration mechanism of concrete exposed to acid rain mathematically, coupling the diffusion of reactive ions and the corrosion reaction. The simulation results and the experimental results were compared and discussed.