This tile in my kitchen became loose a while ago and today I decided to try to fix it but not sure what to do. As you can see from the image link, a fair amount of concrete has come off with the tile. I suppose I can‘t re-use this tile. I have a spare one available. What I need to know is what product do I use to fill in the hole? Should I try to get out all the old concrete stuff first?
Remove as much of the old stuff that you need to fit it back flush with the rest of the tiles then apply thick bed adhesive to the mesh and to the clean part of the tile and ease it on.
Sockies, this is actually an easy repair. The first responder suggested liquid nails. Don't even consider that. If you have a matching tile available, use that in lieu of trying to clean off the tile. First off, it looks like the tile came loose based the non-continuous thinset on the bottom of the tile. If that is the case (which is probably the cause), you want to fill in under the tile with thinset, so the entire area where the tile sets is filled solid from the sub-floor to approx. 1/8 below the bottom of the surrounding tiles. You should remove the existing thinset where the tile will set. You can do this with a brick or masonry chisel. If a little remains at the perimeter, that will be fine. Trying to remove all of it flush with the surrounding tiles may result in loosening additional tiles. You don't want that. Allow about 5-6 hours for that to set (harden) enough to set the tile. You don't make it flush because you will spread additional thinset on the underside of the tile to set it. Use a 3/8 notched trowel to spread the thinset on the entire surface of the bottom of the tile. Place the tile keeping an even spacing from the tile to the surrounding tiles You want the grout joints to be the same size all around. Press down over the entire surface of the tile to ensure it embeds completely and is flush with the surrounding tiles. Allow it to set overnight and remove any thinset that will impede the grout from obtaining 1/4 depth. It's not necessary to make the grout the full depth of the tile. It's imperative to remove any loose grout prior to grouting. That's it. I suggest buying thinset that comes in the bag that you mix with water. Don't make it too soupy when you mix it. The thinset and grout need to (what's called) slake during the mixing process. It simply means you mix it, allow it to set 5 minutes and remix it, and it's ready to use. The bag will have those instructions on the back.
