Abstract: The corrosion resistance of fly ash concrete fully soaked in 2 mol/L NH₄Cl solution as corrosive medium was studied in this paper. Before dissolution, the stomatal structure of fly ash concrete was tested and analyzed. The loss of compressive strength together with the change amplitude and change law of dissolution depth after the dissolution was investigated. Moreover, the structure and pore distribution of concrete after dissolution with different amounts of fly ash (0%, 15%, 30%, 45%) were examined via nuclear magnetic resonance and field emission scanning electron microscopy. Research results manifested that fly ash refined the internal pores of concrete, reduced pore connectivity and improved pore size distribution, which effectively enhanced the structural safety and corrosion resistance of concrete in water environment. Compared with ordinary concrete dissolution area, fly ash concrete dissolution area had ettringite crystals generated inside, indicating that the formation of ettringite can reduce corrosion damage.

Key words: fly ash concrete, compressive strength, time-varying damage, leaching depth, pore structure, micromorphology