Research on The Chloride Diffusion Modified Model for Marine Concretes with Nanoparticles under The Action of Multiple Environmental Factors

Marine concrete structures are subject to the action of multiple environments during their service time. This leads to increased deterioration in the durability of marine concretes under the combined action of bending load and dry-wet cycles, salt freeze-thaw cycles, and salt spray erosion. The main reason for the damage of concrete under the action of the above three environments is Cl- attack. The free Cl- content (Cl-f(-)) and the free Cl- diffusion coefficient (D-f) of concrete can explain the diffusion of Cl- in concrete. This paper considers the actual environment of marine concrete structures and develops the Cl- diffusion modified model for nano-marine concretes under the action of dry-wet cycles, salt freeze-thaw cycles, and bending load and salt spray erosion. The nano-SiO2, nano-Fe2O3, and nano-Fe3O4 were firstly incorporated into ordinary marine concrete, then the Cl- content of each group of marine concrete was measured at different depths, and the Cl- diffusion coefficients were calculated; finally, the Cl- diffusion modified model was established under different environmental factors. The test results show that the total and free Cl- diffusion coefficients of nano-marine concretes were lower than those of ordinary marine concrete, and the nano-SiO2, nano-Fe2O3, and nano-Fe3O4 of the optimum dosage were 2%, 1%, and 2%, respectively. The fitting results of Cl- content have a good correlation, and the correlation coefficient (R) is basically above 0.98.