Evolution of concrete properties under bending and tensile load and acid rain combination

To investigate the evolution of concrete performance under the combined action of acid rain erosion and flexural-tensile loading, this study employed an accelerated laboratory testing approach to examine changes in the appearance, mass, compressive strength, elastic modulus, and neutralization depth of concrete specimens under different simulated acid rain conditions and stress levels. Based on Fick’s first law of diffusion, a multi-factor evolution model was developed to describe the neutralization depth of concrete subjected to both flexural-tensile stress and acid rain erosion. In addition, microscopic morphological analysis was used to reveal the effect of acid attack on the microstructure of concrete. The results indicate that with prolonged acid exposure, increased flexural-tensile stress, and decreasing acid rain pH, the formation of ettringite and gypsum crystals within the concrete microstructure increased, accompanied by the expansion of pores and microcracks, resulting in reduced compactness. During the acid erosion process, the mass, compressive strength, and elastic modulus of the concrete specimens initially increased and then decreased. The compressive strength exhibited the most significant initial increase, reaching a maximum growth of 7.43%, but decreased by 19.49% after 240 cycles of acid rain erosion. The degree of deterioration was proportional to the acidity of the acid rain. Flexural-tensile loading accelerated the degradation of concrete strength, with the most severe damage occurring under highly acidic conditions and high stress levels.