Hello,

You're experiencing efflorescence of your natural stone; salt and minerals appearing due to chemical reaction of cement etc. It sounds as though they've laid on pads hence the circular pattern you see. Efflorescence does fade in time which is why its a good idea to leave your paving for a season before sealing it. Whatever you do, don't apply any acid washes just yet as this can exacerbate the problem by bringing out the natural iron in the stone - it looks terrible!!

Leave it a few more weeks and if you're still unhappy get back in touch with your tradesperson and have them take a look or lay on full beds of mortar (they should've done this anyway).

All the best

Dan

This sounds like efflorescence of the natural stone. It sounds as though they've laid the slabs using a dot and dab method, rather than a full bed. When laying natural stone, I always use a full bed. Efflorescence can fade in time, although this is not guaranteed. As mentioned by another poster, do not seal the patio, and try avoid using harsh chemicals on it as there can be a reaction.
I've seen people using all sorts of patio cleaners, white spirits, jet washing etc to try and get rid of it but unfortunately, time is your best bet.

You would be well within your rights to ask them to come back and relay on a full bed, although the problem is the marks have already appeared and may not totally go away.

I think you do not use any kind of patio cleaner because these staffs just worse for the patio . You have two choose. You can ask the patio shop what they do you to suggest, Next one you can wait until the slabs of patio itself change the situation.good luck Laszlo