Compacting the blocks

[williams]

Right ok. I'm trying to determine what the best course of action is in wet conditions, contractor to contractors I want to find out the best method and talk about what I actually do and what do you boys do?


So when the weather is nice I.e dry blocks AND joints I typically kiln the job up and then wack it, typically 3 to 6 passes.

However I recently was looking on the site and noted that it's better to actually wack without the kiln, I'm struggling to determine though what the process is and I wonder if it can help me when it's wet.

Rain causes us all problems but the biggest is when I need to wack the job, I've tried covering jobs but inevitably the water some how get under the tarps and will drench an area, turning the screed to slop making life hard, sometimes meaning bits need ripping up before I'm finished. It would be easier if I could wack when wet then go back to kiln, which surely would mean no sloppy sand to wack onto.

So I see the wack first method. Would this mean I could compact the job in the wet (as long as screed isn't sloppy) then just leave it until it's dry, go back and then kiln it? Or is it meant to mean wack with no sand then kiln then wack again?

Last two jobs I've compacted 6 times with no kiln apart from round the cuts to keep them still, it's gone down great and then I've just swept kiln in after- how do we feel about that? They are compacted to refusal and not going down any more. Blocks are nice and tight and pass my kick a corner down hard test ( no movement)

I have wacked dry paving before but joints have been damp with kiln first and the kiln just doesn't go in properly, once the joints are wet it just never seems to dry properly, blocks don't pass my kick test, I then hose in the kiln, then go back and re top up when dry, problem is that takes a lot lot more work doing it that way, unless I leave the job with a slurry of Kiln over it which I just can't do.

So how do you boys deal with wet joints/ blocks?

[Tony McC]

There's an urban myth amongst British and Irish paving contractors that paving must be dry before jointing and so must the jointing sand, yet in that Europe, they regularly joint wet block pavements using wet sand, and they get no problems. Amazing, eh?

I've actually used this technique on numerous occasions, and as long as the laying course material is really gritty and free-draining, and the sub-base is genuine Type 1, there's no problem. In Europe, they tend to use a mechanised sweeper to help persuade the sand, which is wetted to the point of being a slurry, into the joints. Probst make a machine to do just this.

So, free-draining sub-layers, sand soaked to saturation and beyond, plenty of sweeping and the result is joints that are well and truly filled, with little or no settlement in those first few weeks, and best of all, it's even easier if it's raining!

I keep intending to make a video showing this technique being used in Britain/Ireland, but then, I have lots of good intentions that I never quite get to achieve - if anyone fancies giving it a go, let me know!

In the meantime, here's a pavement, part blocks, part small element flags, which we laid in Co. Limerick a few years back as part of a training scheme, and jointed in near horizontal rain of the type you only get in the West of Ireland. The results are still there to be seen to this day and not a bother!

[DNgroundworks]

Ive done this before, i found a pressure washer on a low setting worked well

[mickg]

we have use this method for many years and normally on drives if its been raining after you have laid the blocks or the blocks are wet through when you open the packs, you can get 98% of all the joints filled to the top with just a hose pipe and brush

we use a course sand as a laying course so you cant use a vibrating plate the same day if you have forced the sand in with the hose pipe but if the rains stays away then over night the paving will of dried enough to run the vibrating plate over the paving the following morning

obviously use caution when using the vibrating plate, you will know straight way not to continue due to water from the sand laying course being brought to the surface of the blocks paving but like Tony said if you use a free draining laying course this will give ample drainage and not give you any problems

[lutonlagerlout]

I have done it a couple of time with the hose pipe on mist, it seems to work best on drives with a good fall

the thing that is a real pain is when the laying course gets soaked
you start wacking and up she comes through the joints
just had to leave for 2-3 days to let the water soak through

cheers LLL

[Tony McC]

Compact first, then joint - it works much better because the compaction is done *before* the laying course becomes saturated.

By compacting after joint filling using the wet method, you run the risk of fluidising the bed which can result in loss of surface level accuracy.

[mickg]

the only time I use this method is if its been raining and we cant continue working so it makes no difference forcing the sand down as the paving laying course is soaking wet anyway

[lutonlagerlout]

I have been compacting first for 6 years gaffer
if the laying course is too wet the water comes up nice and orange like a volcano
LLL