Concrete - again.

Can anyone suggest an estimate for how long it would take to move a cubic metre of concrete by shovel and barrow? The barrowing distance is only about 10 metres, shovelling into the barrow at one end and tipping directly into the hole at the other. Assume one person, one normal-sized barrow, one shovel---then I can work out how many people and barrows I need to borrow!
Colin

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took 2 of us 4 hours to mix and lay 1.3cubic metres (nearly 3 tons), mixer was at the bottom of the garden about 15m from the entrance to the room but it was all up hill, worked out at approximately 50 barrow loads
LJ

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One person - 3 hours! Based on the figures by 'in2minds' 2 people (but one spent some time mixing) so, say, 1½ people divided by 1.3 cubic metres to get 1 cu.metre. and divide by 3 then mutiply by 2 to get the 10 metre distance - works out at 0.7692306 people. Enlisting this quantity of assistance is not practical, therefore multiply by 4 and you get the time it takes for one whole person to shift that amount - 3 hours. Please by all means double check my figures as I don't want to be resposible for a solid block of immoveable concrete - although I could probably lend you a Kango if the worst came to the worst. :-) Hugh

Colin Blackburn wrote:
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I always did badly at school with this sort of equation, given the ready access to calculators and the invention of the JCB I really didn't see the point of archaic 'how many navvies do I need to' type numeric conundrii.
the real questions is, collin, what's your mass and do you know how to use a sledge hammer, effectively, to disperse a _few_inches of concrete ?
RT

On Wed, 09 Feb 2005 16:34:47 +0000, Colin Blackburn
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Two people, both relatively fit, used to a hard days work. If you go for too many you get in each others way.
As time goes on, it becomes harder, and his harder to shift, I guess you want it moved in an hour or so.
Two people give you some body to work with, keeps you going a bit.
Also you are having this delivered from a waggon, so have the driver empty into barrows for as long as you can talk him into staying arround, cups of tea & bacon butties will help out here.
Don't overload the barrows, you will struggle, best keep it inside sensible limits.
All this is based on my experience of similar activites ...
Tell SHMBO to have the cold beer on standby for when you are finished..... Its an incentive !!!
Rick

Colin Blackburn wrote:
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I work on 6 barrow loads per ton usually. Cubic meter is about 3 tons.
A good navvy could barrow 30 tons in a day, although he needed a load of guinness afterwards.
It's probably a hard days work for a single person, not used to it.
Two of you? should take a hard couple of hours.

An afternoon: I shifted a 1 ton dumpy bag on my own ( shovelful by shovelful into a barrow of course! ) in one afternoon.
Andy.

The Natural Philosopher wrote:
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Assuming you mean a ton, and not a tonne, then each barrowload would weigh 373lbs! Granted there's a fulcrum point (the wheel), but I doubt you could lift or push it!
If you mean a tonne, then its 166kg/barrowload. Still doubtful.

Paul King wrote:
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Yes. I thought about that a bit.
I use 5 bags of cement per ton of sand, and each half bag of cement is a barrow load.So its nearer ten barrow per ton. Although each barrow load has got a lot of water in it.
So I am doing about 224lb per barrow - maybe a tad more.
I can certainly push 2 tons of car. 300lb is probably the limit to control a wheelbarrow.
Its certainly possible to lift a cwt bag - 50kg or so - by hand. That is 1/20 of a tonne.
I would certainly say wheeling a pair is not hard, and three is on.
So somewhere between 6 and 10 barrows per ton.

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Barrowing the concrete and tipping it is the easy bit with somewhere between 1 and 1.5 cu feet to each barrow load. What will make all the difference is whether the barrow is being filled by a contractor (who might not want to wait very long to dump his load), shovelled off the ground or mixed locally in a small mixer.
Estimating the time for shovelling wet concrete is very much like estimating the length of a ball of string. It would vary by at least a factor of 3 depending on how wet it is. I have no direct experience of it but I reckon I can mix and lay about 6 cubic feet of concrete an hour and that includes tamping down and levelling off. Just shovelling it up and barrowing it around I would expect to be able to shift between 2 and 4 times that amount. There are about 35 cu feet in a metre cubed so my estimate would be between 90 minutes and 3 hours.

Okay, everything was in place for getting concrete into this hole this Saturday morning. Then I read of the weather warnings for next week, freezing temperatures, lots of snow. The forecast at the moment is for cold temperatures and snow from Saturday through to Monday with the cold weather continuing into the week. Our house is right in the main area for the first blast of cold weather and we are on an exposed moorland.
So, given that I have read that concrete should be kept above 10C and given that this is impossible to guarantee at this time of year should I shelve the plans?
What would be the consequences of pouring the concrete in cold weather or more significantly of the first few days of its curing being in potentially sub-zero temperatures.
Colin

Don't suppose most of the 'hole' will be that cold - how deep/sheltered is it? Can always insulate it beneath straw & plastic sheeting.

Phil wrote:
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The hole is about a cubic metre. It's below a wall so there is some shelter. It would be difficult to heat---other then by lighting a fire on it!---but I could certainly insulate the top and cover it in polythene. Would that be sufficient

Should be. -5 is forecast , of course that's air temperature, so insulate well (also stops it drying out too fast).

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I can't imagine problems in this situation. Concrete generates warmth as it sets (on the Hoover Dam they had to cast cooling pipes into the concrete) so if the ground isn't frozen and you cover it well all should be OK

Colin Blackburn wrote:
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Nope. Just use winter additive.
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You must protrect it from freezing by using e.g. feb 'wintamix'
It will take an age to set - probably 3-4 days before its even sensibly set, and several weeks for full strength.
BUT its probably going to be better going off at 5C and 95% humidity than 35C and 5% humidity.
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winter slabs are generally better cured than summer slabs up to the point that they are frost damaged so protect the surface and they are fine

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Add an antifreeze admixture and cover with a frost mat, all available at the builders merchants, the frost mat is a layer of insulation so if you have anything handy laying around that will do, if the concrete is ready mixed ask the supplier to put something in the mix.

The ground is warmer than the air this time of year, so dont insulate setting concrete from the ground
NT

snipped-for-privacy@meeow.co.uk writes
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Have you ever heard of concrete being insulated from the ground?? at least not in this country, even in the north of Norway I have only ever tented over and kept warm from above but at our temps a frost mat will suffice