Experimental study on the corrosion characteristics of concrete exposed to acid water containing aggressive carbon dioxide and sodium sulfate

• Properties of concrete suffering from sulfate and aggressive CO 2 attack were studied. • The content distributions of corrosion products in concrete specimens were examined. • Corrosion process of the specimens undergoing the compound attacks was described. • The corroded specimen undergoing the compound attacks can be divided into 4 layers. The degradation of concrete constructions subjected to acid water containing aggressive carbon dioxide (CO 2 ) and sulfate is primarily attributed to the compound attacks of aggressive CO 2 and sulfate. The performance deterioration of concrete exposed to acid water containing aggressive CO 2 and sodium sulfate were investigated in this paper. The changes in mass, relative dynamic modulus of elasticity, splitting tensile strength, and longitudinal ultrasonic wave of specimens suffering from the coupled effect of aggressive CO 2 and sulfate attacks were used to evaluate the performance degradation of concrete. Moreover, the content and morphology of erosion products formed in the specimens during the process of the attacks were studied via thermogravimetry, X-ray diffraction, and scanning electron microscopy analysis. Then, the corrosion depths and the content distributions of corrosion products of these specimens were examined to explore the corrosion process of concrete. The results showed that the performance degradation of concrete subjected to the coupled attacks were more serious than that of concrete only suffering from one type of attack. According to the content distributions of corrosion products, the corrosion zone of the concrete subjected to the coupled attacks can be divided into 3 layers, namely, the corrosion layer, the dense layer, and the transition layer, where multi-decalcification of hydration products, carbonation and dissolution of carbonates and formation of ettringite, and dissolution of calcium hydroxide and diffusion of sulfate occurred gradually from the external to the internal.