Variability of the concrete air permeability coefficient with time

Measurement of air permeability is considered as a realistic indicator of the quality of concrete. This heterogeneous material is composed of a complex network of pores which are partially filled up with a liquid solution. Both pore structure and moisture content in the pores directly affect the permeability of concrete. Therefore, any factor influencing both of these parameters will have an effect on the permeability. Notably, there is a high dispersion of the air permeability coefficient of concrete, even when the environmental conditions are controlled. The time to reach an equilibrium permeability value around 10−16m2 can be more than 18 years. The air permeability coefficient is statistically studied by means of data analyses throughout 20 years of testing. The experimental procedure presented gives reliable information about the change in quality of the concrete in terms of air permeability.