I have a short (24" hi) concrete wall and I want to put a 2" facing of hypertufa on it, so the hypertufa layer will be 2" thick and like 24" tall. I'm using a 3-1 perlite-cement mix. I mix it pretty wet, then mush it in to wet the concrete as good as possible, and just do about a 2" high layer, sort of like making a row of bricks in place.

Questions:

Should I dampen the concrete before laying on the HT?

Should I put a layer of mortar on the wall first?

How long should I wait before I can lay on another course?

What are the potential consequences of only waiting say 5 hrs or so before laying on the next course (like I did for the first couple of courses before discovering the lack of bonding on the top layer - see below)?

I also want a layer on top of the wall. It's like 4" thick and flat on top. I did a test bead, 2" wide and 2" tall, and it seemed to be working OK, though my mix was fairly dry so it didn't seem to be wetting the concrete much, but after curing for a few days I was shaving some of it off to adjust the shape a bit, and it was loose and hadn't bonded to the concrete at all. The HT bead itself was intact and solid, it just hadn't stuck to the concrete. Hope I don't have the same problem with the wetter mix I've been using on the walls since then...

Thanks for your help.

J