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Basic cement/ ballast Q


zoothorn

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Hi- I need help on a basic Q. Approximately how much volume does 1 bag of cement, plus added ballast equate to?

 

I guess its 'dependent on what sort of concrete/ what sort of job'.. so in my case its to fill 3ft wide drainage tubes (+ rebars) > to form pillar footings.

 

Thanks- zoot

 

 

 

 

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6 minutes ago, Onoff said:

Use one of the online calculators like this:

 

https://source4me.co.uk/calculate_concrete_mix.php

 

Thanks very useful Onoff- well my chap wasn't SO far off as I thought: 15bags + 3 tons ballast he said.. & I said to myself WTF? !

 

Calculator says 12 bags + 1.54 tons ballast for the 3 big pillar footings.. plus Ive 5x other small ones to do (3x on upper/ easy side of my slope) + 2 midway.

 

Strewth.

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Worth thinking of ready mix. Just found a place local will do it for £99 cash per cubic metre. Doesn't matter if you want 1/2m3 increments, they'll mix what you want on site. 

 

They don't go as far as Wales though! :)

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What Ive done is go 2 ton ballast (not 3) & 12 bags cement (not 18!) > & just do these 3 big lower pillar footings.. then later, go postcrete for the upper easier ones.. or another few cement bags + the leftover ~1/2 ton of ballast.

 

Ive only got a small area/ shelf Ive created near the job, on the upper part of slope up next to road / for my delivery.. & can't accomadate 3 tons/ dumpy bags + mixer + 18 cement bags you see.

 

cheers

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1 hour ago, Russell griffiths said:

Post Crete will be a very expensive way of doing it. 

 

Ah ok. thx for the tip.. ok will do the other ballast ton & cement bags later. Is it feasable to barrow-mix using these? I won't have a cement mixer you see.

 

The easy upper-side footings I'd hope would 'only' need to be 1/3 size of stream big sods- these 80cm high due to allowing for stream @ max swell.

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17 minutes ago, PeterW said:

 

Don't do this ..!! Postcrete is not structural ..!! Mix it 4:1 and do it properly. 

 

Ok PeterW won't do this then!

 

4 ballast to 1 concrete.. plus a splash of frost-proofer admix stuff, I think is my chap's recipe. But can I mix by hand in a barrow?

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5 minutes ago, zoothorn said:

 

Ok PeterW won't do this then!

 

4 ballast to 1 concrete.. plus a splash of frost-proofer admix stuff, I think is my chap's recipe. But can I mix by hand in a barrow?

 

You can mix up in a barrow...or on a board. I often use a mixing tray for small quantities.

 

https://www.amazon.co.uk/Builders-Building-Material-Children-Plastering/dp/B06XS2FJND/ref=asc_df_B06XS2FJND/?

 

 

 

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Postcrete is also rapid set (very rapid) you won't be able to mix it and pour it, it will set in your barrow. It is designed to be poured into a hole around a fence post dry, and then water poured into the hole. for that it does a good job.

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10 hours ago, ProDave said:

Postcrete is also rapid set (very rapid) you won't be able to mix it and pour it, it will set in your barrow. It is designed to be poured into a hole around a fence post dry, and then water poured into the hole. for that it does a good job.

 

No of course.. probably not right for the job.

 

Ok so as I'm here, & say I'm going with the 4:1 ballast/ concrete + splash mix.. can I just dig a hole in ground & put in? or does it need to be 'contained' in a (maybe smaller dia) section of tubing set into the dug hole. And is rebar neccessary for these? IE these three 'easy' footings will be on the high slope side, actually the ground's somewhat a level 'shelf' here, so the cabin will effectively sit on them (base between).

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If they need anything it will be shuttering around the tops which you can make from a £1 B&Q (other retailers are available) black bucket. 

 

Take the handle off , turn it upside down and use a jigsaw to cut the bottom out around the base ring. Now set it where you want the top of the post, dig it in and level it and just build up soil around to hold in place. Now do a a 4:1 wettish mix, tip into the “bucket form” and tamp it as you go with a bit of timber. Smooth over the top and let it go off for a couple of days. 

 

Then it’s just a case of pull the soil back and lift

off the bucket and you have a nice neat cast top. 

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If your soil is firm enough and you can dig a hole accurately enough size wise then the soil sides will contain the concrete. Go oversize with your hole of course and you might underestimate your quantities. My brother hand dug a hole for his astronomy pier about 3 feet deep and I reckon it was near perfectly square. That's in clay though. Stems from digging holes in the Army I imagine! 

 

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Edited by Onoff
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5 minutes ago, Ferdinand said:

May be worth the mixer.

 

Not expensive ... around 300 for a Baby Belle type, and save a helluva lot of work / time.

 

And you get decent quality concrete / cement.

 

Ferdinand

 

I have thought of this.. but storage tricky, & cost, & I won't use much tbh/ I only really have ~this job to do. I may be able to borrow one.. if I play my cards right.. with a nice n'bor. Yes I do have one!

 

12 hours ago, ProDave said:

 

 

 

 

Edited by zoothorn
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52 minutes ago, PeterW said:

If they need anything it will be shuttering around the tops which you can make from a £1 B&Q (other retailers are available) black bucket. 

 

Take the handle off , turn it upside down and use a jigsaw to cut the bottom out around the base ring. Now set it where you want the top of the post, dig it in and level it and just build up soil around to hold in place. Now do a a 4:1 wettish mix, tip into the “bucket form” and tamp it as you go with a bit of timber. Smooth over the top and let it go off for a couple of days. 

 

Then it’s just a case of pull the soil back and lift

off the bucket and you have a nice neat cast top. 

 

Hi Peter- I like the sound of this idea.. understood. Ok good a few options here & seems not too much of a job for me.

 

@Onoff actually I have pretty heavy clay here so may well be able to get a nice neat square dug/ but I like the bucket to contain idea. Might do a combo of yrs & PeterW's idea.

 

Cheers- I'll come back to this once I'm ready to do them.

Edited by zoothorn
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12 hours ago, ProDave said:

Postcrete is also rapid set (very rapid) you won't be able to mix it and pour it, it will set in your barrow. It is designed to be poured into a hole around a fence post dry, and then water poured into the hole. for that it does a good job.

 

Another thing to watch is that postcrete is fine when a single bag, or maybe two, is used in a post hole, but if you try and use three or four bags the chances are that it will end up cracking.  I found this out when fixing one of our fence posts.  It was on a slope, and the hole ended up larger than I wanted, so I just chucked a couple of extra bags in.  It cracked quite badly, perhaps from the heat build up (postcrete gets pretty hot as it cures).

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Interesting points @JSHarris there.. understood. So sounds like postcrete is too small for the job really. Ok maybe I can dangle some money to 'hire' my n'bors mini-me mixer just for these few footings as of when.

 

Can't wait to get them done, then onto the brackets > pillars & timber base work.

 

cheers chaps.

 

 

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Half a cubic metre is the max amount of concrete to mix by hand and even a quarter is hard work. With a mixer I would not do more than 2 cubic metres even with a labourer unless readymix was not practical.  Concrete is over 2 tonnes per cube, so about 90 small bags of ballast and 18 cement.

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In this weather you need your wits about you to mix and pour quickly whilst the preceding mixes are still wet or it can dry too fast. Thereafter think about covering with a plastic sheet, keeping wet. Tbh it can be too hot to mix up concrete especially if you're new at it.

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you can get bags of ready mix that isnt postcrete and hence goes of at a normal rate.  We might have to do this for our pile caps unless we can get a pump long enough as its 40N (high strength) spec which you cant mix by hand apparently.  Will be using a concrete mixer though and each post is 6 bags

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