Slow-setting concrete ?

[Adrian]

HI All

Installing my new polytunnel out here in the windy West of Ireland will involve casting some 'chunks' of concrete to hold the whole thing down (recommended by the supplier). The concrete profile is about 10" wide, by 9" high - by 14 metres long - down each side of the tunnel - plus across the ends...

Calculations at the excellent _paving expert_ site suggest that I'm looking at about 1.75 cubic metres of concrete - which I don't fancy mixing by hand, or even with my little electric mixer.

So.... wondering about getting the 'readymix' boys in.... Only problem is that a readymix lorry won't be able to get 'alongside' the tunnel site - so they'll need to dump the mix on the ground and I'll have to barrow it to the tunnel.

This will take me a bit of time (!) - so I was wondering if there's an additive they can include in the mix that stops the stuff from setting to allow me time to do the shovelling / barrowing.

If so - what's this magic substance called ? - so's I can ask for it....

Many thanks Adrian

[Cicero]

=============================== You can get pumped concrete in many areas. See here for the general idea:

[Adrian]

neighbour was having deep concrete piles inserted (nasty! )

I agree that it's work - but it's kind of overkill for this job, I think. If I can just make sure that the stuff doesn't set quickly in a heap where it's been tipped, then I think I can barrow it reasonably well.

The readymix lorry can get to within 20 ft of one end of the tunnel - but, as it's all freshly 'shifted', somewhat soggy earth, I don;t think they'd risk getting the lorry submerged in the mud.....

Regards Adrian

[Phil L]

Why not just buy concrete blocks? - these can be handled easily, won't go off and will probably cost about the same...don't forget, sooner or later the polytunnel will need to be removed / repaired / replaced, what do you intend doing with two 14m long blocks of concrete then? - with celcon type blocks, they can be removed, stacked and re-used.

[fred]

In article , Adrian writes

Retarder; not sure how long it gives you or if you can get different times from different ones but that term should let you get started with your supplier.

An alternative would be to use a spot-mix type company, they will mix on site and will barrow a reasonable distance to your pouring location. They use huge barrows and will expect you to be fully set up when they arrive with shuttering and planks for easy access. Note that one chap here had a very bad mix from a company using a a manual mix drum on the back of a truck but I have had good results with a company using a sealed auger type mixer where the mix is mean to be better controlled. I think it was about 200quid a cube. Be aware that the rucks are huge.

[Andy Hall]

I think that the solution could be a lot simpler.

Readymix and Ready Micks.

In other words, find who does a bit of local building and landscaping and get them to show up with four of their mates complete with barrows in exchange for some euros and Liffey water tokens.

[Adrian]

I understand your concerns - but it's a bit more complicated than that...

The polytunnel frame is set up with the 'legs' of the hoops about 6 -

8 inches into the ground. The concrete is then cast above ground in shuttering, so as to surround the legs.

A patent plastic channel is then bolted to the hoops, and then plastic cladding is secured by being trapped in this channel, which is then forced down the hoops until the whole things is drum-tight.

The point of all this palaver is to make renewal of the plastic an easy operation in 5 - 8 years time. The alternative technique is to simply bury the plastic in the ground - but it's very difficult to get decent tension on it then, and renewal of the cladding involves diggin up the old stuff - which is a right pain !

So - the idea is to make replacement of the cladding easy. If it needs to be removed then that's somebody else's problem, and, if the concreting is done right, we can forget about the need to 'repair'...

Many thanks Adrian

[Adrian]

Ah - thanks...... ...mind you - it's probably known by a completely different name out here

Had a long and confusing discussion with a digger driver - which was only resolved when we realised that what he was calling 'a ditch' was what I was calling 'a bank' - and that a 'ditch' in Irish is known as a 'drain'...... talk about going round in circles

Yes - that's another possibility.... I'll do some research. I'm sure I saw an ad from a 'mix it on the back of the lorry' company - I'll have to look it out....

Thanks Adrian

[Adrian]

Oooh ! - bad pun

It's a thought.....

Trouble is - a small voice in my ear keeps saying 'it's only a little bit of cement - you can do it.....'

I'm already 'half-chickening-out' - in that the polytunnel supplier is 'sending a man' to help with putting up the frame, and he's coming back to help with putting the plastic on.

Any less involvement from yours truly and I'll start feeling really guilty - as well as very poor.....

I suppose the other approach is to engineer some means for the readymix lorry to get closer to the actual site. Any idea how far the chute on the back of a lorry will reach ??

The tunnel's 14m long by 7m wide.... - trouble is, if I get the earth 'solid' enough to bear the weight of the lorry it'll require some serious digging before I can plant anything it it after..... need a skyhook or a zeppelin !

Thanks Adrian

[Owain]

Model aeroplane runways?

The base for an experimental scale model of a maglev train?

Owain

[Owain]

Remove the topsoil before concreting, put it back afterwards.

Owain

[nightjar]

it was in the back garden with vehicle access only through a built-in garage in the house (he has lots of bits of old cars that are in a constant state of being restored). It saved a huge amount of work, for relatively little cost.

Colin Bignell

[The Natural Philosopher]

At this time of year it will take a day to go off at least anyway.

A good Irishmen, I once heard, can shovel and barrow 30 tons in a day.

"McAlpines Fusiliers"

[Adrian]

Thanks for the comments

Oh - I'd not thought of that........

OK - so a couple of those should have it done & dusted in about half an hour ?? - got any phone numbers ?

Actually - the Shed Man cometh tomorrow - and as part of his deal to erect a 12' x 24ft shed he's going to lay a 3" slab for it to sit on - be interesting to see if he mixes himself or 'gets a load in'.

If the latter then that'd be a good time to buttonhole the driver & see what he thinks about the polytunnel problem...

Gorgeous sunny day out here in the sticks today - cold, but wall-to-wall blue sky - makes a change from the 24/7 rain, sleet & snow we had last week !

Great song !

Regards Adrian