Damage degradation pattern and life time prediction of solidified red mud under coupled environment of corrosive salt and freeze-thaw cycles

In response to the global issue of red mud accumulation and its environmental risks, this study investigates the damage and lifespan of red mud in harsh environments, aiming to assess its potential as a building material. Utilizing Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Electrochemical Impedance Spectroscopy (EIS), and industrial CT scanning techniques, the research finds that freeze-thaw cycles significantly alter the microstructure, chemical, and electrochemical properties of solidified red mud. SEM analysis reveals that freeze-thaw cycles roughen the red mud surface and increase cracks; XRD reveals a slight decrease in the diffraction peak intensity of amorphous phases (such as aluminosilicates); FTIR indicates that the Si -O -T asymmetric stretching vibration band narrows and shifts slightly to higher wavenumbers; EIS analysis points to a decline in electrochemical performance; CT scans observe an increase in porosity and number, proving structural degradation. Despite only a 1.66 % loss in mass after 10 freezethaw cycles, losses in dynamic modulus of elasticity and strength are notably higher, with strength loss reaching 3.95 %, indicating serious impacts of freeze-thaw cycles on the structure and performance of solidified red mud. However, hazardous element leaching tests show that, even under severe conditions, the leaching of solidified red mud still meets the World Health Organization (WHO) safety standards, demonstrating its environmental performance. Durability assessment using the weibull model indicates that dynamic modulus of elasticity and strength are key indicators, both of which fall below failure thresholds after 40 and 118 freeze-thaw cycles, respectively. These findings guide red mud 's use in harsh conditions, support enhancing its frost resistance, and promote its eco-friendly building material potential.