What to replace swimming pool /spa dam tile with?


I live in NJ and I have a gunnite Carlton pool installed in 2002. In 2004 the tile on the dam top surface between pool/spa peeled off and Carlton repaired in kind. Now tile on dam has completely fallen off. Carlton wants 00 to replace tile in kind, but I'm not keen on tile because of past problem. Questions:
+ Can I replace the tile on the top surface of dam with slate? Any other suitable material?
+ is this a common problem on tiled dams - why does it occur?
Thanks