I'm sorry, I should have been more specific. Due to the nature of glass against glass and the shear factor of silicone, it is the PERFECT glue for aquariums. I have used it to glue wood and stone to glass in wet environments (after curing of course) and usually it has come off within a year. I think the term for the kind of strength that it does not have is tare factor. That's why you can pull it off of things so easily.
Quik-crete has things in it that harden your water and raise your ph. Depending on what you're planing on putting in your paludarium, that could be good or bad. If you're thinking poison frogs and little colorful tetras, as so many vivariasts are these days, you are going to want softer, slightly acidic ph.
You're goint ot need to either A:use an acid to age the concrete or B: let it sit with a filter running for weeks to months to ensure all the chemicals in the concrete, such as lye, have leached out of the mortar to ensure you don't poison any fish or amphibians you place in there.