In article , KK
writes
My patio (about 25 sq metres) is made of bog-standard concrete slabs
laid about 20 years ago. I have a problem with black stains on the
slabs. The stains are roughly circular, about the size of a small coin,
and very difficult to remove. I suspect they are caused by a fungus or
mould in the slab itself, rather than on the surface.

I've tried patio cleaner solution from a DIY / Garden centre (expensive
and ineffectual). I've tried blasting the slabs with a high-pressure
water jet (shifts the surface dirt nicely, doesn't affect the stains).
I've tried scrubbing with a broom and a variety of scouring / cleaning
powders & liquids (Ajax, Flash, Jif etc).
What about Armillatox - under the new regs this is now what it's
labelled to do anyway.
Colin
--
Colin Brook - Winchester (UK)

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