An experimental study on the effect of chloride penetration on moisture diffusion in concrete

Chloride penetration and moisture diffusion are two important transport processes for studying the long-term durability of concrete. The chloride penetration and moisture transfer in concrete are considered as two coupled transport processes. An experimental study was conducted for determining the related material parameters in the coupled transport processes. For the coupled moisture diffusion, we consider that the total moisture fluxJHt is resulted from two driving forces: the gradient of moistureH, and the gradient of free chlorideCf, that is,JHt=−DH-Hgrad(H)−DH-Clgrad(Cf′). In this formulation, two transport parameters are involved: the moisture diffusion coefficientDH-H and the coupled moisture diffusion coefficient due to chloride diffusionDH-Cl. A seepage test was designed specifically for determining the two transport parameters. The test data showed that the chloride penetration accelerates the moisture diffusion significantly. The two transport parameters were determined using the present test data. The result showed thatDH-Cl is not a constant, but depends linearly on the free chloride concentration.