[PSUscaper]

Glue doesn't fail over time due to moisture. It will fail at the beginning because it is too wet to set up. It is designed to be used outdoors. When I go to old jobs, you break the block before the glue gives. These jobs are outdoors being subject to wet conditions ALL year long. Glue may fail if it is subject to CONSTANT moisture.....like perhaps around a swimming pool, but I've seen it keep its hold there pretty well.

On jobs where I've had glue failure, it is not the glue that failed....it is the BLOCK! The concrete the glue adheres too breaks off before the bond of the glue does. If its not the block itself, it is because of excessive shifting, where settlement was so extreme it pulled apart. If there is enough force, something has to give, whether its portland, glue, or the concrete itself.

Portland works BUT it will fail if there is shifting in the project over time, and being that were talking about projects without footings here, they are going to move. Glue is designed to hold while remaining flexible. Portland is not. That is not a good design element for flexible systems.

Also, I'm not sure why poly sand is being brought into the discussion because it is not designed to be a adhesive. It may have adhesive properties, but I don't know why it is being brought up in this dicussion of adhering tread stones to block. Poly sand doesn not keep moisture out. It keeps some out, but not all. A sealer would be needed for that, and I'm not sure any sealer is going to gurantee a 100% barrier.

I agree portland is cheaper, but really, how much are you saving by using it over glue on a project? Are 10 tubes of glue breaking the bank on a project? Plus, what about the time associated with having portland, mixing portland, applying portland, cleaning up portland, cleaning up the tools, cleaning up the bucket, etc., etc......compared to putting a tube of glue in a caulk gun and squeezing the trigger????? I see a LOT of portland jobs that are done with excess dripping on the front of blocks. Glue is much easier and cleaner.