Spongy ground a nightmare

[rab1]

Its actually been a good winter up here, wet but no wetter than normal (think pissing down most days but no snow)

[williams]

Ok it's happened again

Dug the job out and actually covered it all up with a tarp because I knew heavy rain was coming. Went in today, took tarp off, ground was a. Bit wet but not too bad.

Type one delivered, spread it and felt ok underfoot, compacted it just once and it's was like a blancmange! Worst I've ever seen in my life.

So it appears it's not the ground it's the soaking wet stone that's being delivered. Spoke to the bloke who does me the stuff and he's using it as well as they also have a paving company, when asked how they get round it he told me they just crack on!
I'm not exaggerating it's like jelly!

It's just 25m so went and got 11 bags of dust and hand mixed it all into the type one and it appears to have dried it out enough. I have left it needing to be topped up by about 75mm so hopefully will be ok now.
Covered it again tonight as the rain was silly so hopefully tomorrow it will be solid.

Honestly never had these problems before

[GB_Groundworks]

change your agg supplier, piss wet through mot is no good, goes thixotropic with vibration

[Kuts]

try your bitmac supplier/local plant, i get mot cheaper than the recycled shite.

[cookiewales]

in the wet use lean mix am starting a job in ashstead surrey soon 180m2 setts ground clay 18m3 lean mix £1800 keeps site clean as well

[lemoncurd1702]

I've commented on this in the thread to "wet for block paving". Spread cement dust over the first layer of compacted base, final layer more cement and then compact. The cement from the first layer pumps up during compaction. It's not so much to make the base stronger, though it does also have this effect, but the introduction of cement dries the base material. I would also dust the sub-grade if not using terram.
You can also rotavate cement into the base before compaction but don't make concrete.

I've never tried this but apparently lime (specifically quicklime) applied to the sub-grade will dry the soil, maybe it would do the same for a sub-base.

Another method is to use clean 40mm and compact stone dust into it, do this in layers.

If your base is already down keep compacting it to bring the water to the surface brush the water to the lowest point or if your lucky the sun may shine. Regardless of the weather the base will eventually stiffen and I would go as far to say that it will be a better base than one done in the dry.

[Tony McC]

it's the soaking wet stone that's being delivered

There is a limit on the moisture content for Type 1 to be compliant. If they are delivering sodeen aggregate, refuse delivery on the grounds that it is outside the moisture content parameters of the spec.

Obv, the wagon driver will pull his face, but the stone is no use to you in that condition - he might as well deliver putty!

[Tony McC]

Spread cement dust over the first layer of compacted base, final layer more cement and then compact. The cement from the first layer pumps up during compaction.

You have to be wary of reducing the permeability of the sub-base. If the sub-base becomes less free-draining, it could result in the laying course becoming saturated which, in turn, causes liquefaction and movement of the block surface.

And you need to be ultra-wary about 'pumping'. If there is *any* risk whatsoever of pumping sub-grade material into the base, even if it is accompanying the cement, it could cause more problems with drainage and introduce a structural weakness.

[lemoncurd1702]

Yeah I understand this Tony I've seen what happens to blocks laid on a concrete base.
I'm not trying to make an inflexible base I don' chuck that much cement at it, just enough to move the job forward. It may reduce permeability a little but not significantly enough to cause problems. Nothing has come back to bite me on the butt as yet.

Any thoughts on a no fines concrete or permeable bitmac with a terram layer to separate the laying sand.

[williams]

The problem here in Essex is that a plant closed down, think it was one beginning with a b?
Anyway all the stone now comes from the same place afaik. All the places I know have this stone, the only other option is crushed which generally is not all that, I have seen some nice stuff but more often than not it's got that muddy dirty smell, I'm convinced it's mud....

Makes life very difficult.

Anyway, went in today and it was fine, put another layer of type one on top and it's perfect (thank god).

I would imagine that 2 bags per ton isn't turning the base into a concrete base, that's something like a 11:1 mix I reckon.

[williams]

That said it was bloody hard work knocking up 6 ton of compacted base with 11 dust :0

The idea of doing a layer, chucking some dust down, then another layer sounds quite reasonable though, ultimately all you want the dust to do is take up the wetness of it really.

[lutonlagerlout]

in fairness one of the best block pavers i ever saw "tom togher" before his truck got wiped out by an artic on the motorway
always used 12:1 dry leanmix as a sub base
theres a drive near me he did 15 years ago and its still true today
i dont know the physics of it but it worked for him for years
LLL

PS he has the allotment next to me now and I didnt recognise him for 3 years,only when i saw an ultrascape bucket we got chatting
isnt that mad?

[Tony McC]

No fines is a well-understood construction and is one of the recommended methods for permeable paving, but there's nowt to stop it being used for conventional paving. I'd certainly prefer it to permeable mac, which I still think is over-priced.

The only real concern I would have with a no-fines base in place of a flexible/unbound sub-base is that sodding geotextile to prevent trickle-down. I've seen what happens when geotextiles create slip and it scares me. Admittedly, it's an unlikely scenario on a driveway, but I wish there was some other way.