Grouting concrete slabs

[j007]

Hi, I have just pressure washed my patio slabs (450x450) and removed weed etc. I now need to fill the gaps but not sure which method to use. I have previously use kiln dried sand and brushed it in the gaps but this doesn't last that long (maybe 1 year) and the weeds grow back really quick. I have read that it is advised to use a dry mortar/cement mix but I wanted to know how long would that last and if that prevents weed growth a lot better than kiln dried sand?

If dry mortar/cement mix is the way to go then what exactly do I need? Do I just need some sharp sand and cement at a ratio of 3:1 without adding any water? My area size is approx 30m2 so how many bags of each would I need? Also do I just make the gaps damp (not the top of the slabs) and then put the dry mix in? Do I need to spray some water on top after I have set it in using a pointing tool? Some help would be much appreciated.

 

[Wayners]

All I can tell you is push it in with a tool and finish it off smooth.
Seems to help if mix is a little damp.
You can use cheap wide masking tape along either side of joints to keep clean.
Yes you can spray a mist of water on final smooth off.
The problem is the width off gap. Is it wide enough to fill?
Resin fillers also need pushing in otherwise filling is just at the top and they disintegrate.
No easy answers or permanent solution to slap joint filing

 

[aveatry]

I add fibreglass strands to a wet mix of 3 to 1 sharp sand mixed 50/50 with kiln dried sand but I sometimes sieve the sharp sand as I find that there can be some bigger grit in there which makes it tricky for the thinner joins. The reason for the kiln dry sand is that other wise i find the normal sand very red in colour and i end up with pink joints.
I also use gaffer tape to mask off each side of the slab joint then I can wack the wet mortar in there without trying not to get it on the slab face. I use a flat 10mm or 5mm wide pointing trowel to pack it and smooth it off.
When it has dried on the masking tape - which is pretty quick I pull it of and hover it up with my titan wet and dry vac that i use for any building work.
And then I go a step further and add waterproof cream or a stone sealer to the join when dry. Its the longest lasting and cleanest method i have tried but you need a gap big enough to actually get the mix down there.
I find cloth gaffer tape the best to use as it needs to be really sticky as there will be dust and grit on the slabs before you even start. The cloth gaffer tape can be ripped in half lengthways as you do not need the 50mm width which makes it go a little further.