# Forum Home Renovation Sub Flooring  Bagged Concrete Mix for Stump Pads ?

## buzza1

Hi All, 
Yet another question for you guys. 
I am building an extension which needs about 24 stumps. I'm worried that if I get readymix and pour into each hole, it would have set before I have finished placing the stumps 
Can I use a bagged concrete mix instead and would it have the same strength as raedymix. I know its a little time consuming though ?  
Or am I worrying over nothing and do I order the readymix a little "wet" (dont know the exact terminology) 
Thanks
Chris

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## Bodgy

Can't give you the tech specs on ReadyMix v bags, but with ReadyMix you state the grade u want. For this low grade work tho you just take the cheapest. 
Reason for posting was that the slabs for my sheds were laid respectively from ReadyMix and bags of concrete ex Bunnies. 
The Readymix is rock hard but I noticed when I was chiselling some drainage channels for the 'bags' slab it was noticeably softer, easily flaking off. The concrete was laid about 8 months ago so not still green. 
In your shoes I'd get the readymix and some mates to help, plus a slab or two of beer.

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## wands

Chris, 
The concrete truck will have water, thus you can ask him to make it really wet. What you really need is a few extra hands. One to barrow the conc and you and another to be setting the stumps, at worst just you setting the stumps while the mrs barrows. Ask the driver to pour half or quarter barrow loads. You may have to pay extra if it takes longer than 15 minutes. And don't be afraid to tell him to take back what you don't need, but he will get ####ty if it is his last load. Use a string line, go row by row (start with the furtherest) You only need to set the stump so that it is barely touching the string line. You'll be surprised how fast you'll be able to do each one. Besides, depending on the soil, you will have more time than you think to work it. 
I'd hate to be mixing all the bags you'd need, you can use them, but it will be a hell of a lot more work. 
Cheers, Steve

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## Shaun04

Dont make the concrete to wet, making it to wet affects its strength. Most people think concrete is just concrete, its not, dont make it so wet if the stumps are taking load.

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## Gumby

We had about that many for our new deck and did them all with bags. No stress about getting all the stumps in before the concretet truck wanted extra time, took our our time to set the stumps just right etc etc. 2 bags per hole, could get the consistency just how we wanted it and easy to do. 
It's now holding up a spa with 1500L of water in it with no problems at all.

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## Wardy

hi chris :Smilie:  unless youv'e got 2or3 barrows,then i'd suggest bags.use rapid set bags, they set in 15 mins. i've used these at work for log barriers, sign posts.put the first bag in dry add some water,spear down around the mix with a spud bar so the water mixes in,put your next bag in add the water  spear down through the mix with the spud bar again so the water seeps in. the less water used the stonger the concrete will be.(something to do with oxygen molecules in the water, the more water the more air gaps between the aggregate and sand which causes weaker concrete)
cheers :Smilie:

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## Gumby

I don't think I'd use rapid set for stumps. Use normal.

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## scooter

Agree, rapid set not suitable for structural work.

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## Shaun04

About to say the same thing, structural work is not to be messed around with aye  :Rolleyes:

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## echnidna

I used to put in 60 stumps from a minimix in 1 go by myself.
24 stumps in 1 go of minimix would be easy as long as;
all the holes are clean 
and the stumps just sitting in the holes 
with stringlines up, 
all you have to do is barrow concrete and lift stumps to the line

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## bpj1968

Concrete usually has 2 specs 40 mpa and 20 mpa.  40 for structural, so premixed bags are okay, but rapidset is only 20. 
If you use 2 bags per stump, that's 48 bags at about $300.  Have you considered hireing a mixer, a metre of sand, and aggragate and a few bags of cement.  Or if you would have future use, maybe buy a cheap mixer.

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## Pulse

Readymix is actually available in any strength, 20, 25, 32, 40Mpa are common ones. Most driveways etc are 20Mpa, some factory floors are 32Mpa for example. Rapiset is not structural and less than 20Mpa. 
Adding water on site is a big no-no, read www.concrete.net.au, everything you need. 
Cheers
Pulse

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## julianx

> If you use 2 bags per stump, that's 48 bags at about $300. Have you considered hireing a mixer, a metre of sand, and aggragate and a few bags of cement. Or if you would have future use, maybe buy a cheap mixer.

  this sounds like the best option to me

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