Ran the pressure washer over the patio today. No idea how long it's been there but quite a while and it clearly hasn't ever been washed before. Pressure washing might have been a bit over-vigourous as some of the aggregate is showing but I've no way of knowing whether they were always like that. The colour wasn't really visible before (just dirty grey) but now they're buff when they're wet and closer to light grey when they're dry. The buff colour looks better so I was thinking a coat of patio sealer might help bring the colour out and stop it getting quite so grubby in a hurry. The paving expert site seems to quote PU as the best formulation, whereas the 'normal' stuff is acrylic. Not cheap (about a fiver per sq m for the Cementone stuff at my BM), so I was wondering if anyone has used it on concrete slabs and whether it did a decent job.
Cheers