Durability of concrete subjected to acidic exposure attack under flexural loading

Durability of concrete under the combined exposure of acidic environment and flexural loading has been studied. Concrete specimens were made and subjected to 168 days exposure to the flexural loading (stress levels of 0.0, 0.35 and 0.5 of their 28d flexural strength) and acidic exposure environment. Concrete properties including neutralization depth, mass change, compressive strength and flexural strength were measured. Compositions of samples were determined by means of x-ray diffraction and chemical analysis. Microstructure of samples was conducted using scanning electron microscope. Results indicate that with the stress level rising from 0.0 to 0.5, the performance of concrete deteriorated gradually and the deterioration of the tension zone was greater than that of the compression zone; concrete performances improved within 28 days and afterwards deteriorated dramatically; acidic solution reacted with cement paste, leading to the formation of harmful gypsum and the decomposition and dissolution of hydration products of cement; the increase of stress level increased the porosity of concrete, accelerating the rate of acid erosion, which led to the deterioration of concrete performance.