Dave Baker wrote:
Any good for patios and driveways or is it useless? At 30p a kilo
from Tesco for the value stuff it's a damn sight cheaper than
anything else I can find. I used to use sodium chlorate when you
could still buy it although the weeds always came back next year.

Failing that what's the best way to deal with weeds in A) block
paviour patio and B) gravel covered driveway?

it does kill weeds but it has drawbacks.
It leaves white deposits which will walk into the house.
It kills other plants, some of wich may not belong to you.
It makes pointing or re-pointing difficult as salt has an adverse effect on
(wet) cement.
It also is corrosive to steel and iron.
It's not good for garden wildlife