The Brew Cabin

i recently lifted and relayed my patio. because of its size (86m2) i opted to grout the patio with a dry mix. I made sure it was fully compacted and soaked it down. it has been about three weeks and the mix (5:1 plus dye) does not appear to have fully set. it is hard to touch but when i tried to jet wash the patio it started to lift the grouting so i quickly stopped. Have i done the the grouting wrong? will it have to be redun or can i strenghten it somehow? Or am i pressure washing too soon?

Cheers

Will
Will

A dry mix grout never really works unless it is used with a mortar-buttered joint. Any other use tends to fall apart in a matter of weeks.

The problem is that, with no access to water, the cement content starts to hydrate in a piecemeal way, and so the outer 'skin' of the grout hardens before the inner content has been dampened properly. Further, because the cement is not properly dispersed through the mix when it is wetted, it doesn't bind together the sand grains as it would in a traditional mortar.

If you are using buttered joints, and the dry grout is brushed in more or less immediately, and then tooled to ensure it's firmly packed and hard, then it does tend to work, but a dry mix in a dry joint....waste of time and money, I'm afraid.

There's nowt you can do to salvage the existing jointing. It's had it. The cement content has already hydrated, it can't be un-hydrated and re-set, so the only real fix is to rake out the lot (a big nail in a stick makes a great tool for raking out loose jointing) and start again. The method shown on the Pointing Case Study page is probably your best bet.