Pools, Spas and Hot Tubs - Pool - Mastic for stone coping to concrete?

I have a gunite pool with flagstone coping and adjoining concrete deck--all about seven years old. The original mastic between the stone and concrete is now shrunk and cracking and needs to be replaced. The pool contractor had a sub come in at the very end and put some sticky black stuff in the gap and spread some white sand over it.

The questions now is: What should I use to replace it? The gap is about 1/2" wide by about 1" deep. Should I put backing material in the gap to minimize shrinking?

Thanks.

Brent
Atlanta, GA

the caulking needs to be replaced from time to time, they ( the kits ) come in colors, grey, white and black. pool contractors use #30 white silica sand once they pour the caulking in, it self levels.
you tyically should have either a white expansion foam about 1/4 to 3/8 below the coping / deck line, so your fill with the self leveling caulking is about that deep. you want to remove all the old caulking, razor knife it clean, vacuum out any debri, and set in foam or some sort of foam fill backing rod ( if needed )before mixing the kit. you also will want to masking tape a clean line on both sides of the gap to be caulked as the caulk sticks very well and is tough to remove. Keep a small can of xylene or toluene handy. Most of the time the kits are a poly urethane 2 part. You have a short time between mixing to pouring. Spread the silicone as you go, though it may sink in here and there, you may want to see if it sticks or sinks as you spread the silca sand. once done with caulking, carefully remove masking tape, there is no tooling of the joints required.

DECK-O-SEAL Polysulfide Sealing Compound (http://www.wrmeadows.com/wrm00157_.htm)

that's the stuff i use, I get mine in kits from a company called White Cap supplies

Thanks for taking the time to provide a very helpful detailed reply! I have tried for some time to figure this out and have gotten nowhere.

Enjoy Labor Day!

Brent
Atlanta, GA