Durability of marine concrete doped with nanoparticles under joint action of Cl- erosion and carbonation

Marine concrete is susceptible to seawater erosion and sea tides. Specifically, concrete in tidal areas is influenced by the joint action of Cl- erosion and carbonation, resulting in severe structural corrosion and reduced durability. In this study, nanoconcrete was alternately subject to immersion and carbonization in 5%NaCl to investigate the influence of nanoparticles on the durability of marine concrete under the combined action of Cl- erosion and carbonization. The free Cl- concentration and carbonization depth in concrete were considered as test indexes to evaluate the durability of nanoconcrete under their combined action. The concrete microstructure was analyzed via SEM and XRD. The results demonstrated that the use of nanoconcrete significantly reduced the carbonation depth for the same cycle number. The free Cl- concentration of nanoconcrete at 0–5 mm depth, 56 N cycles, and 2% and 1% nano-SiO2 and nano-ZnO content was 19.3% and 17.6% lower, respectively, than that of normal concrete. Microscopic tests revealed that nanoparticles could optimize the concrete pore structure, generate C-S-H gels, and make the internal structure of concrete dense. Consequently, the addition of nano-SiO2 and nano-ZnO to concrete can significantly improve its resistance against the joint action of Cl- erosion and carbonation, and effectively enhance the durability of marine concrete.