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Measuring gas permeability

Gas permeability tests measure the flow of a gas into the concrete under the action of a pressure gradient.  It overcomes some of the disadvantages of measuring water absorption that include:
 - In concretes that are not fully hydrated, water alters the permeability to be measured
 - A measurement cannot be repeated in the same location
 - The viscosity of water is approximately 100 times greater than that of air, with volume flows
    being far smaller
 - With water, only overpressure can be measured

Tests include the Schonlin air test, Surface Airflow Test (SAT), Vacuum test,  Torrent test, Hong-Parrott, Figg air test, and Autoclam.

Acknowledgement: Concrete Society

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TR31 Permeability testing of site concrete