Numerical simulation of air permeability in covercrete assuming molecular flow in circular tubes

Torrent's testing method is extensively used for measuring the surface air permeability of concrete. However, the equation for the coefficient of surface air permeability adopted in the test has not been well validated. We numerically simulated the surface air permeability test assuming molecular flow in different number of circular tubes of different radii. Our numerically obtained coefficients agreed well with the theoretical one and also with Torrent's coefficients of surface air permeability when the correct porosity was input. The relationships between the surface air permeability, pore (tube) radius, and porosity (effective area) were summarised. (C) 2016 Elsevier Ltd. All rights reserved.