Why does my slate tile have a chalky white residue on it?

Question

I have a slate tile patio on the back of my house. One of the tiles has formed a chalky white section. This section is also weaker and is beginning to crumble.

I've tired washing the white substance off with water, and while it looks like it washes off, when the tile dries the white stuff is still there.

Does anyone know what is causing this and/or what I could do to stop/neutralize it?

Answer 1

It's probably lime leaching up through the stone from a concrete surface underneath. If so, it's probably permeated the stone and there's not much you can do about it. Maybe try a slighly acidic solution (vinegar and water) on it to neutralize the alkaline lime.

Answer 2

Usually that is lime in the mortor mix.......wash with acid and seal.......if you can afford it.......good luck.