As per subject, what size is a 'bag' these days and the rough cost of a 'bag'?
Supplier worked out the job would need approximately 7 'bags' and delivered 7. I've just looked and they are what I would call 'half bags' 25Kg at around £3-80 per bag rather than the equivalent of 1cwt or 50Kg.
Is 7 half bags enough for the 2 cubic metres of concrete I specified?
The price is ok, but what do you want it for? The use determines the volume made up.
EricP submitted this idea :
The foundations for a small light out building.
Think that's what they call a 'bag' these days - Health and Safety, maximum lifting weights and all that.
David
The message from Harry Bloomfield contains these words:
Bags have been 25Kg for some years and I for one have been glad that the building trade has got decidedly wimpish as I got older. :-)
Depends how strong you want it but I don't think 175Kg of cement would go very far. At 1:3:6 (which is pretty lean) I think that would make about half a cubic metre.
2 cubic metres of concrete is nearly 5 tonnes in weight: You'd need about 3 times that much cement
Have you looked at getting it delivered by a "mix on site" truck - would be a lots quicker for foundations than mucking about with a small mixer
Charlie
Not really. I used to use about 5 bags to the ton, and you will need about 4 tons..
What do you think? Work out the volume you need for whatever you're using as aggregate. See Cormaic's site.
Harry Bloomfield was thinking very hard :
It seems my supplier has indeed miscalculated :-(
Thanks for the replies!
25kg is the standard bag these days...
Depends on how strong you want it... For a medium strength mix like C20 you would need something like 700kg of cement and 3600kg of ballast.
Loads more infor here:
Have you actually used one of these firms? Have a look at the thread I started called "Mixed-on-site concrete - a warning" (April 2006) to see why I I'll never use this sort of outfit again.
I used that for about 2/3rd of a cubic metre recently.
In article , Autolycus writes
That was an appalling story Kev, at the time I got the impression it was an open drum mixer hung off the back of a lorry, manually loaded so subject to all sorts of operator screw ups - accidental or otherwise. Was that the case?
My limited experience of site mixed concrete has been of a huge truck with sealed component compartments, a sealed auger at the back and little for the operator to screw up, a lever controls the strength of the mix but other than that it looked pretty foolproof. Maybe this type would be more reliable, it certainly worked well for me. Alternatively if your outfit was using one of these, I don't know what to think.
I haven't seen a bag larger than 25kg in years (excluding tonne "bags").
25kg is the largest item you are allowed to carry alone, so is the standard maximum weight for loads of things these days.Christian.
The truck that my cowboys used was a 6-wheeled Volvo (that dripped oil) with ballast in a hopper almost the length of the wagon body. A conveyor under the hopper loaded ballast, under operator control, into a drum mixer mounted on the back of the truck, and powered by hydraulic motors driven by a pump on the lorry's main engine. There was a water tank, with its outlet to the mixer again manually controlled by the operator (the water tank, incidentally filled up on my metered water). I didn't see exactly what the lad did when he clambered into a compartment almost at the back of the lorry, but it appeared that he was emptying bags (or, from the strength of the ensuing mix, probably bag) of cement into another hopper, and thence into the mixer drum. This may (I'm not certain) have been the only method of controlling the quantity of cement used. The operator claimed the mixer was 1/3 cubic metre capacity, and based his claim for extra payment on the assumption that he had completely filled it for each mix.
The brilliance of the design of the whole shebang is illustrated by the fact that the lorry had to be parked with its back wheeels on two lumps of timber to get the mixer high enough to tip into a standard builders' barrow.
Couldn't be any worse.
Lucky b..
In article , Autolycus writes
Thanks for the extra info, looks like there's potentially a lot to screw up in that method. Think I'll carry on recommending the concept but if you aren't around to beat me to it I'll be warning of the dangers of open mix over the mix in the sealed auger.
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