Permeability of concrete under stress

Permeability tests were carried out on concrete specimens subjected to a compressive stress. Special emphasis was placed on understanding the influence of stress application on the permeability on concrete at early ages (1-3 days). It was found that the presence of a compressive stress below a certain threshold value decreased the permeability, but when the applied stress exceeded this threshold, a significant increase in the permeability occurred. Permeability increases due to an applied stress also appear to depend upon the overall stress history.