"John" wrote in message
...
I bought a load of chinese granite "Bianco Cordo" about 1 cm thick 30 cm x
60 cm.

It's polished white/grey granite. They are placed outside where rain,
frost and
temperature ranges from -20 (january) to +30 (right now). After having set
some
plates I noted the granite plane color change slightly. It was probably
mortar
moisture seeping from below. The polished top did to get any moist. Next
day the
discoloration has disappeared. It probably just evaporated since its +30
centigrade now.

Will there be problems in winter? Will the granite crack from frost
changes? I
thought granite behaves well in winter.

Since the tiles darkened, they absorbed water. Bad news when it freezes...
Unless you seal the whole area religiously you might be in trouble. That
might mean every year.