Concrete Foundation Shuttering

chickens and wheat

Member
Mixed Farmer
Well i aint no mathematician but the wider you go the more concrete required, the more concrete the more pressure ?
In theory not the pressure at the bottom of a 6 ft high wall of wet concrete is the same matter how thick the wall is,

drill a hole in a water tank 6ft below full level and the water will squirt out with just the same power whether the tank is 3 10 20 or 50 ft in diameter.

Saying that more to go wrong/more money spent on a wider wall so use stronger shutters, theory and reality dont always match
 

chickens and wheat

Member
Mixed Farmer
poured the day before chicks arrived, after a little accident with the old block wall. pins drilled into base slab, should be stronger. Luckily the biomass pipes escaped unhurt.
shutter.jpg
 

mar

Member
The force is only the depth of the concrete. A 200mm wall 1200 high will exert the same force on the shuttering as a wall 10m thick.
A cheep way is too build the shuttering pegged into the ground like a fence, wire the 2 sides together through the ply and cut the wire to remove the shuttering. iyswim.




If you poured a 6 inch slap 40 feet wide would you need stronger road forms than one 4 foot wide?


it all depends on the angle of repose, the lower the slump the less pressure, the higher the slump, more pressure https://en.wikipedia.org/wiki/Angle_of_repose

A wall 10m thick by 1200 high will exert a lot more pressure on the shutters than a wall 200mm thick by 1200 high.

The pressure on road forms in a 6 inch slab at 40ft wide is likely going to be the same as a slab 4ft wide.

Imagine you had a slab 40ft wide and 6 inch deep, pour the concrete, level it of and remove the road form immediately and the side will fall away, the whole 40ft isn't going to just collapse, just a strip around the edge

Repeat the same on the 4ft wide slab and the same width will collapse, it is only the bit that has collapsed that is exerting the pressure

 
Last edited:
it all depends on the angle of repose, the higher the slump the less pressure, the lower the slump, more pressure https://en.wikipedia.org/wiki/Angle_of_repose

A wall 10m thick by 1200 high will exert a lot more pressure on the shutters than a wall 200mm thick by 1200 high.

The pressure on road forms in a 6 inch slab at 40ft wide is likely going to be the same as a slab 4ft wide.

Imagine you had a slab 40ft wide and 6 inch deep, pour the concrete, level it of and remove the road form immediately and the side will fall away, the whole 40ft isn't going to just collapse, just a strip around the edge

Repeat the same on the 4ft wide slab and the same width will collapse, it is only the bit that has collapsed that is exerting the pressure


Less pressure with a higher slump? I thought it'd be more cause a 40 slump concrete will more or less stand up by itself where as a 120 slump concrete runs like water
 

Stock

Member
Less pressure with a higher slump? I thought it'd be more cause a 40 slump concrete will more or less stand up by itself where as a 120 slump concrete runs like water

Slump test is all about water. More water the higher the slump. Concrete mix is designed so much water to cement to sand and aggregate.
So if one wants a 25n mix it comes with the required amount of water, if you add water you weaken the mix.
A high slump also means a very fluid and easily worked concrete. HOWEVER if an admixture is added then the slump test is useless and different test is carried out.

For shutters one looks for a low slump and if one is pouring a large volume of concrete in to a shutter is is controlled to prevent overloading the design of the shutter and to prevent overheating of the concrete (weakening the wall). Once concrete is mixed the chemical reaction begins and continues for the life of the concrete. After a period of time the mix starts to support itself again reducing the load on the shutter.
Again one needs to be careful with the type of cement used in the mix, CEMII cures normally but cement containing GGBS cures slowly requiring the shutters to remain insitu longer and is fine for composite floors but not for every floor.

So make sure you know what you are getting in the truck...........................................
 
Slump test is all about water. More water the higher the slump. Concrete mix is designed so much water to cement to sand and aggregate.
So if one wants a 25n mix it comes with the required amount of water, if you add water you weaken the mix.
A high slump also means a very fluid and easily worked concrete. HOWEVER if an admixture is added then the slump test is useless and different test is carried out.

For shutters one looks for a low slump and if one is pouring a large volume of concrete in to a shutter is is controlled to prevent overloading the design of the shutter and to prevent overheating of the concrete (weakening the wall). Once concrete is mixed the chemical reaction begins and continues for the life of the concrete. After a period of time the mix starts to support itself again reducing the load on the shutter.
Again one needs to be careful with the type of cement used in the mix, CEMII cures normally but cement containing GGBS cures slowly requiring the shutters to remain insitu longer and is fine for composite floors but not for every floor.

So make sure you know what you are getting in the truck...........................................

I know how slumps and slump tests work (y)
 

Steevo

Member
Location
Gloucestershire
Thinking again about this. Will it need longer than the usual 28 days to cure?

Shuttering almost completed now. 18mm ply, chunky timbers, threaded bar to tie it together, and some steel supports too!
 

SFI - What % were you taking out of production?

  • 0 %

    Votes: 77 43.5%
  • Up to 25%

    Votes: 62 35.0%
  • 25-50%

    Votes: 28 15.8%
  • 50-75%

    Votes: 3 1.7%
  • 75-100%

    Votes: 3 1.7%
  • 100% I’ve had enough of farming!

    Votes: 4 2.3%

Red Tractor drops launch of green farming scheme amid anger from farmers

  • 1,285
  • 1
As reported in Independent


quote: “Red Tractor has confirmed it is dropping plans to launch its green farming assurance standard in April“

read the TFF thread here: https://thefarmingforum.co.uk/index.php?threads/gfc-was-to-go-ahead-now-not-going-ahead.405234/
Top