Filling a 75l tub with concrete

AboutLee · 19 Mar 2017

Hi guys I posted before about making a ground anchor in a tub for my motorbike security. Now what would be the best way to fill about 70l of the tub with concrete? I've never mixed concrete before and guessing it would need to be a bit watery for it to settle?

I was looking at that ready made post mix and maybe adding some gravel to strengthen the mix and maybe some chicken wire to bond it together?

Would I need to do one bag at a time? Or could I put like 4 bags in mix with gravel and water and let it set?

Thanks.

flameport · 19 Mar 2017

You can mix it all in one lot - if you are up to shifting the substantial weight of it and can mix it all before it sets.
In reality you will need to do smaller batches.

If buying postmix do not add anything else - the whole point of that product is that you don't need to.
If you want to have specific things in it, buy the cement, sand and whatever else separately.
In any case, use the smallest quantity of water to get a decent mix.

4 bags of postmix is nowhere near enough for a 70 litre bin.

DaveHerns · 19 Mar 2017

1 bag of Postmix filled a 10 litre bucket when I was making some bollards so you'll need 7 or 8 . I'm not sure if that amount in a big tub will go off uniformly, others will know. It's going to be heavy though!

foxhole · 19 Mar 2017

Best to mix the concrete [around three bags should be enough]with cement on the ground and fill container dry, sprinkle with water from a watering can, the less water used the stronger the cement.

Doggit · 19 Mar 2017

Postcrete is easy, but not cheap, but 3 bags at Wickes for £4.59 each will give you a 60Kg lump, and that may be sufficient. If you want to go for the full 70Ltrs, then you'd need 4/5 bags of ballast, and a bag of concrete, and mix a bag of ballast at a time with about 5Kg of cement, and then add it to the tub as you go. I assume you have a post to set centrally as you go. The postcrete will go off in a couple of minutes, whilst the ballast will need supporting till the mix goes off.

Interesting method Foxhole, I've heard of it for doing posts, but haven't had the courage to try it yet.

ntb · 20 Mar 2017

70L of concrete is going to be around 160Kg. Make sure your tub is where you need it before filling.

AboutLee · 22 Mar 2017

flameport said:
You can mix it all in one lot - if you are up to shifting the substantial weight of it and can mix it all before it sets.
In reality you will need to do smaller batches.

If buying postmix do not add anything else - the whole point of that product is that you don't need to.
If you want to have specific things in it, buy the cement, sand and whatever else separately.
In any case, use the smallest quantity of water to get a decent mix.

4 bags of postmix is nowhere near enough for a 70 litre bin.

I want it heavy enough that it can be moved without my bike chained to it. But heavy enough that both the tub and bike locked together cannot be moved. And 4 bags was a guess lol.

If I did it in batches could I use mesh or something to bond the mixes together?

DaveHerns said:
1 bag of Postmix filled a 10 litre bucket when I was making some bollards so you'll need 7 or 8 . I'm not sure if that amount in a big tub will go off uniformly, others will know. It's going to be heavy though!

So basically 1 bag per 10ltr? Not planning on filling the whole tub, just enough to have some basic plants in it to make it look pretty lol

Doggit said:
Postcrete is easy, but not cheap, but 3 bags at Wickes for £4.59 each will give you a 60Kg lump, and that may be sufficient. If you want to go for the full 70Ltrs, then you'd need 4/5 bags of ballast, and a bag of concrete, and mix a bag of ballast at a time with about 5Kg of cement, and then add it to the tub as you go. I assume you have a post to set centrally as you go. The postcrete will go off in a couple of minutes, whilst the ballast will need supporting till the mix goes off.

Interesting method Foxhole, I've heard of it for doing posts, but haven't had the courage to try it yet.

£4.59 cheaper then buying all the materials separate? And yer Ive had a friend bend some 20mm rebar which ill be sinking two bars in making it 40mm thick hehe.

ntb said:
70L of concrete is going to be around 160Kg. Make sure your tub is where you need it before filling.

From what I was told before its something like 2.4 x 70 x 0.75 = 126kg / 19stone.

Thanks for all your advice guys. Roll on payday on getting it setup.

ntb · 22 Mar 2017

Definitely heavier than that unless you use lightweight aggregates. Typically has a density of 2.3 to 2.4 so 2.3*70 = 161Kg

rsgaz · 22 Mar 2017

AboutLee said:
From what I was told before its something like 2.4 x 70 x 0.75

Last time, the 0.75 was in the equation I gave, because you only wanted your 110litre tub to be three quarters full.

Semi portable ground anchor

Gaz

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Filling a 75l tub with concrete

Doggit

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