Corrosion of Concrete Structures Exposed to Industrial Coal-Fired Flue Gas

Coal combustion of industrial production will release large amounts of SO₂ and CO₂ gases. High concentrations of acidic gases will accelerate the deterioration of concrete corrosion, leading to premature failure or damage to structures. To investigate the corrosion behavior of concrete structures exposed to industrial coal-fired flue gas for 12 years, this paper tested the concrete's macro-mechanical properties, pore structure characteristics, and micro-properties by in-situ and laboratory tests along the height and depth. The test results indicated that the concrete exhibited significant uneven corrosion along the height of the structure. In the severely attacked region (28.6-39.1 m), the neutralization depth in the concrete was 1.4 times greater than that in the slightly attacked region (0-6.6 m), and the porosity was 5 times higher. Different corrosion mechanisms were occurred inside the concrete along the corrosion depth direction. In the shallow concrete zone (0-8 mm), sulfation was predominant, with gypsum (Gyp) as the primary product. The pH was below 8.0, and the sulfate ion (<inline-graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="./online/j.gyjzG24092302-I003.jpg" href="./online/j.gyjzG24092302-I003.jpg"/>) concentration at the exposure surface reached up to 5.5%. In the coexistence concrete zone (8-14 mm), both sulfation and carbonation were presented, with the pH increasing from 8.0 to 11.0. Above 14 mm, <inline-graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="./online/j.gyjzG24092302-I004.jpg" href="./online/j.gyjzG24092302-I004.jpg"/> and Gyp were no longer detected. At 10 mm, calcium carbonate (CaCO₃) was found, and its content gradually increased. In the deep concrete zone (14-18 mm), carbonation was the dominant process, with CaCO₃ as the main product.