To ensure that you get a true test, it is important that the RILEM tube is properly attached to the area you wish to test. If you don’t get a good seal between the putty and the wall, you might get a false fail (leaking through the putty).
Note: Ensure that the inner opening is not obstructed with putty. Putty is resusable. Store in a cool place.
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RILEM How To prepare a RILEM tube for testing