Study on the microscopic transmission characteristics and coupled erosion depth of tailings recycled concrete under the coupling effect of carbonization and salt-fog

In ocean and salt-lake district, especially in some industrial areas, concrete structures suffer from the coupling erosion of carbonation and salt-fog. As an eco-friendly material, tailings recycled concrete(TRC) has been used to its alleviate the deterioration of living environment. Based on series of physical and chemical equations of hydration, carbonization and salt-fog erosion, this paper introduces parameters such as hydration rate, carbonization rate and Friedel salt degradation coefficient. Then，a comprehensive analysis method that can reflect the erosion performance of TRC quantitatively is established, and the microscopic transmission characteristics and erosion depth calculation method under coupling effect are studied. The results indicate that aggregates have a “blocking effect” on the diffusion of corrosive substances, resulting in higher concentration around the front edge of aggregates, and the erosion of salt-fog plays a leading role under the coupling effect. Overall, the CO2 concentration decays faster than that of Cl−. The longer the erosion age, the higher the CaCO3 content, while the content of CH and CSH is approximately inversely proportional to that of CaCO3. In addition, the method for determining the depth of carbonation and salt-fog erosion under coupling effect is studied, and the calculated values are in good agreement with the experimental values. It shows that the coupling erosion depth is greater than that under single erosion, which leads to the salt-fog erosion depth increased by about 30 %, the longer the erosion age, the greater the erosion depth. The effect of iron ore tailings(IOT) on coupled erosion depth is similar to that of single erosion. The results also show that the coupled erosion performance of TRC can be analyzed by using the model proposed in the paper.