Concrete garage base

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I want to lay a garage base at the bottom of my garden, for my motorbikes. It is 25 metres from the road side so delivery of pre-mixed concrete will be a problem, or expensive, or both.
I can mix the concrete myself using a cheap to hire mixer but I need some advice on the amount to lay in one batch, to avoid cracks.
The slab will be 6m x 4m x .125m = 3 cubic metres.
The mixer spec says it can mix 85 litres in 6 minutes.
Assuming I'm just tipping the concrete straight into the ready prepared area, with a bit of tamping and smoothing, I can probably mix and tip about 12 loads = 1 cubic metre, in 70 minutes, with possibly 20 mins more for actually shovelling all the ingredients into the mixer.
This means I can lay one third of the base in about 1.5 hours.
So, help needed here :- What is the best way to do this?
I'm assuming I can't just lay the whole base over a space of 1.5x3 hours 4.5 hours as the concrete at one end will have started to go off before I've finished at the other end?
Should I lay 2 slabs, 2 metres wide each, with a 2 metre gap between them? Then, I could wait a few days until they have both gone off then fill in the gap with another slab? Will this be prone to cracks between the 3 separate sections?
Any ideas anyone. All comments and advice greatfully received.....
Cheers James
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Don't fully fill it at any point but gradually build up the thickness evenly over the whole area until finally you are able to build up to the final level and tamp down with comparatively few mixes. This will ensure that you are able to move the top layer around sufficiently to properly level it, because the concrete at the top will all be fairly fresh.
Move all the ingredients as close to the base as you can before you start and don't skimp on the assistance. There's nothing quite like being totally shonkered by hard graft and having to keep going because you CAN'T stop. Been there, done that!
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So you think the whole slab can be layed in one session, even if this takes 6 hours? Would it not be prone to cracks?

lol. I'm kind of looking forward to doing the graft as I'm trying to lose some weight at the moment!
Yes, the ingredients will have been moved to the site beforehand, probably over the space of a *number* of days.
You are right about the assistance - probably mad to attempt it myself in one day. I can think of 2 mates who'll help me out, which raises another question - given that the mixers are only about 25 a week to hire, would I be better off getting two, and with the help of the mates lay the slab in double quick time? Would this help prevent any cracking?
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James wrote:

I'd do it in strips, as you suggested. I've done a few, without any problems. As long as the underlying base is firm enough and the slab thick enough, the slabs will bond together with no cracks.
I find the break, waiting for the mixer to finish, is a chance to get a breather, get the kinks out of my back, before going on..
I am surprised that the total cost of getting it pumped, ready mixed, is only double. I would jump at that...Buying readymix is so, so much easier, so, so much faster and the quality is so much more consistent than mixing your own.
However, your shuttering has to be all in place and absolutely perfect. I'd still do it in strips, whipping out the intermediate shuttering after getting a rough level on the two outer strips.
--
Sue





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lol, I see your point :-)

376 for ready mix delivered - not including waiting time to barrow it to bottom of garden, estaimated 90 barrows!!!
734 for it pumped, again not including waiting time!!
I reckon I can do it for 300 if I mix it myself, not including the 25 for a week's hire of mixer, and couple of crates of lager for hire of two mates :-)

So you'd put the middle strip in straight away, while the other two are still damp?

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James wrote: <snip>

Sorry, my misunderstanding - I thought you were saying you could get pumped readimix for twice the cost of the materials to do it yourself.. Still, the prices ae surprising - it only cost me 70GBP extra over the roadside price to get a load pumped about the same distance.
It's like when you get your first washing machine or dishwasher, it spoils you for life..

Well, not straight away. I would start early, get the outer strips done, stop for a generous lunch and then remove the intermediate shuttering and pour the central strip. If you haven't put in too much water, a couple of hours is enough for it to hold its shape with that depth of material. Just run a trowel vertically along the edge of the shuttering to release it, before pulling it away, or it might pull some material away with it (no big deal, but the lines showing where the strips join will have a wander in them)..Just level across the centre strip to the outer ones, but do it gently.
--
Sue















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There is a big difference here between morning (first round)pump costs and afternoon pump costs. You might investigate your costs on this basis.
______________________________ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net

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In a previous post James wrote...

Rent a line pump and do the job in one day.
Yes, it will be more expensive, but you will get a better result and you will save your back since you won't have to haul 3 cubic meters of sand, gravel and cement by hand.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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I don't mind doing the hard work as I'm trying to get fitter anyway! I'll move the stuff to the site at a leisurely pace over the preceeding days.
I got a quote for ready mix to be pumped into position and it was twice the cost of me doing it myself.

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penny wise ? Mixing consistent concrete and placement is critical to a successful job. Pound foolish ? Just don't hurt yourself or your Mate, he may not want to be as fit as you towards the end of the day
kickstart
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You're not going to get fit, you're just going to get knackered. I would split it lengthwise, ie do one lot of 2m x 4m, then do the other lot when it's set/when your back isn't hurting so much.
And don't forget your estimates of time to do the job are going to be way out because of all the messing about with shuttering, haven't got enough nails, now the hosepipe's leaking, can't find a washer for it, now the wife's saying the video won't record, your neighbour comes round to borrow something you can't find, the cat has been sick, etc etc, the list is endless.
Steve
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This is what my question really comes down to - will it crack if I do it in strips? Do I have to wait for the strips to completely go off before putting another one next to it?

lol. I'll build in contingency time then!

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[snip]
Another option is to rent a gasoline engine powered wheel barrow that in the US is called a "concrete buggy". It will carry about 1/4 yard and you walk along behind it as you go from truck to work site.
I did a concrete pad once like you are suggesting. Fifty bags of premixed concrete (60 lbs each). Empty 2 bags into the mixer, mix, dump into the wheel barrow, place inside forms and smooth. By myself since the guy I hired to help didn't feel like showing up. Not the slightest frickin' shred of a chance I would ever do it again. Hurt like hell for about two weeks.
Rent a buggy, buy the concrete mixed.
Steve.
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Talk with your local concrete supplier. Here in the states they have trucks that employ "hoses" to pump the concrete over (fairly) long distances (don't know the maximum length.) Be a lot easier than mixing yourself and get a better set.

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Listen up everyone that is thinking of mixing there own concrete for a situation such as this. Or anythng over 1 yard
======IT WILL NEVER PAY TO DO IT YOURSELF. HIRE A TRUCK AND OR A PUMP.=====

You for got things like roding the concrete to make sure it is at the right level and if it is not having to go back and move material from another area or rake it up closer. You forgot bullfloating it to get the rocks down after its is roded you for got running the edger along the forms for the first pass....plus much much more this all takes time and must be done at a certian "set" time in the the process. Mixing and pouring and mixing and pouring will greatly interupt this process...can it be done yea sure but how much do you want to do it again when it fails in a year or so? Look if you want to do it this way do very small sections at a time and place rebar dowels at the edge of the slab ready for the next pour. You can drill holes in the form and place the rebar in these holes the next day take these forms out and pour up to it and repeat. BTW you dont necessarialy have to do one pour a day you can do as many as you can just make sure to finish the process with the previous one first then move on to the next one. Butting slabs together is not the problem its not tending to the already poured concrete that is the problem......
if you figure just the materials you are already so close to the cost of redimix it is not worth the hassel...time is also money......
James wrote:

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Can you explain what running the edger along the forms for the first pass is? Creating a smooth edge around the slab or do I have to separate the slab from the form?

Fair point. I will do smaller slabs and ensure I have lots of mates around to help.

Can I start the next slab while the one I'm butting up to is still damp without risking cracks? Or do I have to let each one go off before I start the next?

Mixing myself the cost will be about 300. Having readymix delivered to the roadside will cost 370 but that does not include the time the truck has to wait while the mix is wheelbarrowed 25 metres down the side of the house and through the garden to the work site. 3 cubic metres is about 90 barrows full so that will take a couple of hours, even with plenty of help.
Waiting time for the truck is 70 per hour adding another 140 minimum, which is almost doubling the cost and is a hell of a lot of heavy shifting to move 90 barrows full, all against the clock as the concrete is going off during those 2 hours whilst being moved.
I have a quote of over 730 to have it pumped to that is still too expensive given I can mix it myself for less than half the price.
Conclusion : If I mix it myself in small enough batches I can ensure a good quality mix each time and do the whole project for significantly less money than approaching it any other way.

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James wrote: Conclusion : If I mix it myself in small enough batches I can ensure a good quality mix each time and do the whole project for significantly less money than approaching it any other way.
Good luck !! Try finding a friend who knows something about pouring concrete. Trying to pour a garage slab when you haven't any idea of what you are doing, is a recipe for disaster.
--
JerryD(upstateNY)



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Thanks for the warning! I'm trying to avoid disaster by doing my homework and asking the right questions in the right places :-)
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Hi Keith
I've found a local company with the same kind of lorry and am waiting for them to get back to me with a quote.
I've also found a local ready mix supplier that can tip the 3 cubic metres at the roadside, 25m from site, for 275 which is cheaper than I can buy the materials from my builder's merchants for!
They say there is a plasticiser in the concrete allowing for 4 hours workability, but I'm still not sure me and a couple of mates could shift so much in 4 hours! My slab is 150% the size of yours at 16' x 18' x 6"
How far did you have to move your concrete in the barrows? My site is 25m from the roadside. Do you think it could be done in the time?
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James wrote:

Sounds as if you are getting nearer to a solution.
Unless the ground between is steep/uneven/difficult the wheeling is not that much of a problem, with good, not overfilled, wheelbarrows. Keep the weight forward so that it is taken by the wheel and not on the handles and even a girly can manage. A good barrow, properly filled, will balance when full, so your arms are only used for steering and pushing, not lifting.
Preparing the route, right to the tipping points, is the vital thing. If you can set up a raised walkway down the middle of the slab, so that you are always tipping the barrow downwards, most of the effort disappears. Establish a circular route, so you can tip, straighten and go on rather than have to turn around.
Do that and, provided that you (and your mates) are fit enough to keep /walking/ for 4+hours without a break - no problem. If any of you could actually manage a marathon without dying, then you will have time to spare..
But, if your back starts hurting, you are doing it wrong - too much weight on your arms and your back not straight. Keep going and you could do yourself a lot of harm.. Do it right and your legs, OTOH, will be screaming by the end..YMMV..
--
Sue









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