Deterioration of mode II fracture toughness, compressive strength and elastic modulus of concrete under the environment of acid rain and cyclic wetting-drying

Abstract

There are some concrete structures subjected to both impacts of acid rain and cyclic wetting-drying, such as the concrete bridge pier and dam in an acid rain zone, and therefore, it is of great significance to study the deterioration of concrete material parameters under such combining impacts. The parameters investigated in this paper mainly include the corrosion depth, mode II fracture toughness, compressive strength and elastic modulus. Additionally, the chemical composition and thermal stability of corroded products distributed in severe, mild and free corrosion zones were measured by using X-ray diffraction (XRD) and thermogravimetric analysis (TGA). To study the pure mode II fracture toughness of deteriorated concrete, anti-symmetrical four-point bending (ASFPB) tests were conducted on the corroded concrete specimens. The test results indicate that the dissolving corrosion caused by H+ occurs in the corrosion zone of concrete, while the swelling corrosion caused by SO42- mainly occurs in the severe corrosion zone. The thermal stability of corroded products distributed in the severe, mild and free corrosion zone of concrete decreases gradually. The pure mode II fracture toughness of concrete almost decreases linearly with increasing the number of cyclic wetting-drying, and increase with increasing the pH value of simulated acid rain. Moreover, there is a good linear relationship between pure mode II fracture toughness and compressive strength of concrete under both impacts of simulated acid rain and cyclic wetting-drying. The elastic modulus of corrosion concrete decreases with the increase of wetting-drying cycles, and it decreases with decreasing the pH value of simulated acid rain solutions.