As long as the patio is sound concrete, you shouldn't have any problems. Here's a couple of tips: Clean the concrete well with Muratic acid to remove any residue that may affect the bond. Use a polymer additive instead of water when mixing the thinset mortar. This will add strength and water resistance. Use a sanded grout and again, add the polymer additive instead of plain water. Make sure the tile doesn't set up too quickly or the bond will not be as strong as it should. Apply plastic sheeting over freshly laid tile and after grouting so the thinset and grout "cure" instead of dry. This is extremely important and will result in a long lasting quality job. Good Luck.