Chloride Transport in Undersea Concrete Tunnel

Abstract EN

Based on water penetration in unsaturated concrete of underwater tunnel, a diffusion-advection theoretical model of chloride in undersea concrete tunnel was proposed.

The basic parameters including porosity, saturated hydraulic conductivity, chloride diffusion coefficient, initial water saturation, and moisture retention function of concrete specimens with two water-binder ratios were determined through lab-scale experiments.

The variation of chloride concentration with pressuring time, location, solution concentration, initial saturation, hydraulic pressure, and water-binder ratio was investigated through chloride transport tests under external water pressure.

In addition, the change and distribution of chloride concentration of isothermal horizontal flow were numerically analyzed using TOUGH2 software.

The results show that chloride transport in unsaturated concrete under external water pressure is a combined effect of diffusion and advection instead of diffusion.

Chloride concentration increased with increasing solution concentration for diffusion and increased with an increase in water pressure and a decrease in initial saturation for advection.

The dominant driving force converted with time and saturation.

When predicting the service life of undersea concrete tunnel, it is suggested that advection is taken into consideration; otherwise the durability tends to be unsafe.