I have a house in Thailand. It is 10 years old. It has a terrace of 97 square meters. It is covered with 33x33 tiles. I used to wash the tiles with a pressure washer but not too long ago something less pleasant happened. A while after I washed, I noticed that some tiles have lifted. When I looked closer, I saw that about 20 were loose when I tapped on them. After a while, more became loose, totaling about 40. I'm pondering what to do and come up with the idea of using PL60 from a tube, which doesn't build up. I start using this but after a while, I see that the tiles have come loose in new areas. Then I give up. It needs to be completely redone. I consider why this has happened and come to the following conclusion. The tiles are not set in tile adhesive but in cement! When I sprayed, water seeped in where the grout was poor. Then the water caused the tiles to lift. The tiles are now gone, and new ones are to be laid. Then there is a problem. The cement base, which is indeed even, has many dents. To avoid using too much adhesive, I have started filling the dents with thin mortar, which I spread with a wide steel spatula that I've taped to a handle. It works well. But then I wonder if it will be strong enough to attach the tiles. It's 30+ degrees here, so it dries very quickly. And how is it, is mortar a lime mortar? So my question is, do I need to make it stronger? If I need to, how do I make it stronger, what can I mix in? Should I mix in cement or some other additive from Sica? I don’t want to mix sand and cement but start from mortar which has a fine structure. I have already applied this to more than half of the area, can I retrospectively apply a product to make the base stronger?
