A Numerical Method For Prediction Of The Water Permeability Of Concrete

The water permeability of concrete is an important parameter for the quantitative durability assessment of concrete. Therefore, it is not only of great theoretical significance but also of a certain value of reference for the durability design of concrete materials to study the permeability mechanism of water in concrete and to understand the effects of the pore structure, cracks, and the arrangement of aggregates on the water permeability of concrete.Based on the finite difference method and by introducing the artificial compressibility algorithm, the Navier-Stokes equations for three-dimensional incompressible viscous flow are solved in a numerical manner. A cubic unit cell is used to simulate the flow of fluid in concrete. The velocity field and pressure field of the cubic unit cell are obtained through an iteration algorithm. According to the darcy’s law, the water permeability of concrete is calculated. The validity of the numerical method is verified with some examples.The effects of the shape, aspect ratio and roughness of pores on the water permeability of concrete are discussed. It is found that aggregate shape is the most important influential factor and that the water permeability decreases with the increase of the aspect ratio and roughness of pores. By introducing the lattice theory and considering a cubic unit cell, the water permeability of concrete is obtained for several lattice arrangements of aggregates, which indicates that the arrangement of aggregates is an important factor that affects the water permeability of concrete. According to the fractal theory, the effect of the fractal coefficient of aggregate on the water permeability of concrete is studied. It is found that the relative water permeability of concrete decreases as the fractal coefficient increases. The effect of spherical and cubic aggregates on the water permeability of concrete is also discussed. For a given aggregate volume percentage, the relative water permeability of concrete with spherical aggregates is larger than that with cubic aggregates.