After cementing new patio base, surface is powdery and you can brush away the surface with a broom, over and over again!
Trying dustproofer at the moment, just wondered if anyone else has come up against this same problem!
It was all mixed with a electric mixer.
any help would be appreciated

davey, May 2005

Also cement could be low on active chemicals - or the incorrect mix - try adding active chemical quicklime but wear protection.

Nyge, April 2011

Too much tamping down will bring the cement to the top and this will dry off leaving a powdery surface. Only light tamping is needed to level the surface. Not much you can do other than maybe remove the top inch or two and screed with sharp sand or fresh concrete without tamping down excessively.

Denis Langley (flatcat15), May 2005