Resin artificial rock construction?

[Coral Hind]

The issue is that its friable unless you use the right stuff. Give it a year or two in a marine environment, especially if you are just using it as a mortar, and it will crumble. Fairly sure you can get some high tensile marine environment stuff that is fine offname brand - but at this stage I'm going for the emarco stuff and just using that.

I have not found it to be friable but more indurated. You must not be mixing it right, not using enough cement. I've been using the same homemade concrete rocks I made back in 2000 and they have not crumbled at all. I used regular portland cement from Home Depot.