Design of an in situ steady-state permeability test to determine the air permeability of covercrete

An in situ permeability test method that does not require assumptions for the uni-directional flow has been developed to determine the air permeability coefficient of the near surface concrete. The proposed method involves applying a constant pressure head to a surface mounted ring and measuring steady state air flow rates. The analysis is based on modification of the flow net theory, which needs a calibration factor accounting for the influence of specimen and ring geometries. Effects of test area, width of seal, depth and width of test specimen were investigated using numerical simulation of air flow. The results indicated that the value of the calibration is very sensitive to change of testing area which needs to be corrected for a specimen with a depth less than 50 mm. The experimental studies suggest the duration to achieve the steady state depends on the quality of the concrete tested and the applied pressure. The results indicated that the test method is capable of identifying the difference in quality of concretes.