I damaged the colored sanded grout in my shower floor while trying to clean it with a lime deposit remover. The damaged area has an extremely hard crusty covering that I can't remove even with a grout saw. What to do?

Try a hammer, chisel, sweat and alot of cussing.

I removed some old grout from my tile using muratic acid. Used full strength on the grout for 1 to 2 minutes and it loosened it so I could chip it out. May be helpful.