Bilateral chloride diffusion model of nanocomposite concrete in marine engineering

[Display omitted] •The general equations of bilateral diffusion were derived and verified.•A bilateral diffusion experiment equipment was developed and used in the test.•Chloride distribution is obviously different under unilateral and bilateral diffusion.•The low concentration side will suffer more adverse erosion with bilateral diffusion.•Nano-concrete is anti-bilateral diffusion better, especially high concentration side. In this paper, the behavior of concrete block under bilateral chloride ion diffusion in marine environment was studied, and the bilateral diffusion and unilateral diffusion of chloride ions in nanocomposite concrete and ordinary concrete were compared. Based on Fick’s 2nd law of unilateral diffusion and the application conditions of the error function (erf), the general equation of chloride under bilateral diffusion in concrete was established. After the modification of concrete by nano-composite, the resistance of concrete containing nanotitania to the bilateral chloride ion diffusion was compared with that of unmodified concrete. The diffusion experiment equipment with different concentration on both sides was developed and a series of comparative experiments were carried out. The results show that the bilateral diffusion enhances the diffusion process of chloride ions in concrete compared with the unilateral diffusion, which is also in good agreement with the calculated results of the diffusion formula established in this paper. Compared with ordinary concrete, nanotitania concrete has better resistance to chloride diffusion. The advantage of nano-concrete in the resistance to bilateral diffusion is obvious, especially in the side with relatively high chloride concentration solution.