Rilem Vertical Tube

Before and after surface treatments - If it is determined that a treatment to reduce surface absorption is beneficial then a Rilem Tube test before and after the surface treatment would indicate a relative differential measurement related to surface absorption.

Comparing surface porosity - When surface porosity is being considered a possible source of interior moisture problems, applying the Rilem test method on the exterior surface of the related problem area provides a standard for testing other similar surfaces to determine if the problem area has a greater porosity. The Rilem test should be applied to exterior locations on the same building - on the same elevation exposure, with the same material, etc. - trying to match all of the same conditions as the problem area with the exception of no interior moisture problems. If the surface porosity measurements of the areas with no interior problem matches or are similar to the surface measurement of the problem area, it is a likely assumption that surface porosity is not the problem.

Comparing efflorescence - When efflorescence is visible on the surface of the masonry material, it typically indicates that moisture has been traveling through the masonry substrate picking up soluble salts along the way and then depositing them on the surface where evaporation of moisture occurs. Visible surface efflorescence typically does not occur where the absorption condition is strictly a surface process. Not enough soluble salts are available within that absorption / desorption zone for efflorescence to accumulate. The area of efflorescence should be cleaned of the crystalline contamination in order for the Rilem Tube adhesive to be able to secure the tube appropriately to the surface. Once that is achieved, a comparison of the absorption measurement at the efflorescence area compared to a non-efflorescence area can be undertaken. The existing elevated salt content in an area of efflorescence may increase water absorption in the surface and may also cause a visible ring of moisture to spread out from around the area where the Rilem Tube tube is in contact with the wall.

Comparing porosity of building units - The traditional logic of building a masonry wall is that the mortar joints are more porous than the building units, i.e.: bricks, blocks, stone, etc. If a masonry wall has been re-pointed with a mortar that is harder and allows less moisture to migrate through it then the path of least resistance becomes the building units themselves. In these situations the surfaces of the bricks (or other masonry units) can be seen to deteriorate leaving the mortar joint proud (extending beyond the deteriorated surface of the masonry units). Using the Rilem Tube test for measuring the surface porosity of the building units compared to the surface porosity of the mortar joint would be an appropriate application when these conditions are observed. This test may also be appropriate on proposed mortars prior to approving materials for a re-pointing project.