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Old 02-15-2015, 01:30 PM   #1
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Pouring a concrete slab


I've done some smaller simple concrete work before but looking to do a 10x24 slab this spring for a shed. So I have some knowledge of concrete but never done anything this big where a simple hand trowel couldn't finish it. Have a couple of questions about the process and tools I need to buy. Forms I think I can handle, set level and stake. Will be using 2x6 for forms most likely. Bring in gravel for base and level and compact. Will run some rebar or mesh.

Now for the concrete. Will be getting a truck to deliver, I roughly figured 3 yards but when I actually form it up I will get a more accurate measurement. Will be wheelbarrowing the concrete so will have 3-4 guys to help me. so once the concrete is in the forms I plan to use a board run on the forms to level it out. This is where I'm not really sure on the steps to finish it right. Do I need a vibrator to go around by the edges to not have any voids? After you screed with a 2x4 or 2x6 board do you then use a bull float like this on a pole to smooth it out, http://www.menards.com/main/p-2366139-c-8954.htm? And a little hand magnesium trowel like this for the edges, http://www.menards.com/main/tools-ha...36-c-8954.htm? Do you run the bull float right away after your screed it level with a board?

Is a bull float a good enough of a finish or do I need something like a fresno trowel to go back over it and smooth it out better? When is the correct time to round over the edges? And when to use a groover to cut the control joints, http://www.menards.com/main/tools-ha...31-c-8954.htm? I think the broom finish will come last right?

Anything else I'm missing here? Anyone have a list of the order of steps for finishing a concrete slab? Just trying to do my homework and get a list of tools and other things I will need to buy. Thanks

Last edited by ponch37300; 02-15-2015 at 01:42 PM.
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Old 02-15-2015, 05:05 PM   #2
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The usual mistake for a rookie is having the concrete too stiff because someone said if it isn't stiff it looses a bunch of its strength. Inexperience and stiff concrete shouldn't be used in the same paragraph much less the same sentence.

With a slump you can work with a vibrator won't be necessary on a 6" pour. Just vibrate the forms with a hammer to bring a little cream to the form, all will be well and you won't have rock voids that are so common with stiff material.

These walks on a sand base are only about 2-1/2" thick in the center, wheelbarrow mixed using Quickcrete bags. No steel at all and an idiot fork lift operator loaded to the hilt with asphalt shingles runs up on it. No cracks at all. A compacted base is the answer and some pours don't even need steel.
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Old 02-15-2015, 09:47 PM   #3
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No need for a vibrator. Most of the guys I poured with that did exclusively flatwork didn't even own one. Bull float it right after screeding it.

Sounds like you've done your homework. Most of the tools can be rented, I'd do that unless you plan on doing more concrete work.
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Old 02-16-2015, 09:32 AM   #4
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Float after screeding but don't trowel until the slab has stopped oozing water and any water shine is gone. Ron
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Old 02-16-2015, 10:14 AM   #5
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Thanks for the replies. So screed it all level and then bull float right away. Screed is to get level and bull float is to get somewhat smooth right? Then wait until no water oozing and then trowel it, by hand or with a fresno trowel or both? When do you finish the edges by rounding them over? When do you use a groover to cut grooves into the slab?

I don't mind buying the tools. Really only need a bull float and poles and fresno trowel and a broom to put on the pole. Have everything else from doing smaller concrete jobs around the house before. I'll rent the plate compactor because I won't use it enough to justify the cost. But I'm sure I'll use the bull float again and it's not too expensive. As long as it ends up being cheaper then paying someone else to do it then I still come out ahead. That's the way I look at it.
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Old 02-16-2015, 03:07 PM   #6
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You've got the right idea. Here's a few additional recommendations:

- Make sure to order air entrainment in the concrete in our region.

- You don't need a fresno/walking trowel if you're going to do a broom finish.

- You'll want a jointer/groover that's at least 1/4 the depth of the slab, so in your case, 1.5" deep. Most people just saw cut the following day.

- If the shed consumes the entire pad, and is stick built construction, you likely want to add a thickened edge/grade beam around the perimeter. Grade beams with 2 rebar continuous are the most common, and code approved way, to allow adequate support under a detached building.
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Old 02-17-2015, 03:04 PM   #7
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If it where me..
I would put 2"-3" drainage, lay the plastic, then concrete brick every 2' on plastic, wire mesh on brick, then pour.
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Old 02-18-2015, 06:39 AM   #8
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no steel or wire mesh in a 4" slab,,, by the time the conc jabonies finish walking thru the mud, the mesh is displaced & does no good

http://www.concreteconstruction.net/...-floors_2.aspx - good read

Last edited by stadry; 02-18-2015 at 06:52 AM.
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Old 02-18-2015, 10:35 AM   #9
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Quote:
Originally Posted by stadry View Post
no steel or wire mesh in a 4" slab,,, by the time the conc jabonies finish walking thru the mud, the mesh is displaced & does no good

http://www.concreteconstruction.net/...-floors_2.aspx - good read
If you weren't willing to place steel in a slab for a shed that size in this state, you wouldn't pass inspection........
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Old 02-18-2015, 10:47 AM   #10
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interesting,,, so if #4 bar's used, you're placing a 4 1/2" slab in order to comply w/aci's specs ?
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Old 02-18-2015, 11:00 AM   #11
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If the building is big enough, it get's a thickened grade beam around the perimeter, generally 8-12" thick. Even if that's not the case, the OP mentioned 2x6's for forms, so I'm assuming a 6" thick slab.

Lastly, if the OP were to use a VB under the slab, you don't need 2" of cover on the under side according to ACI........
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Old 02-18-2015, 05:33 PM   #12
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Quote:
Originally Posted by stadry View Post
no steel or wire mesh in a 4" slab,,, by the time the conc jabonies finish walking thru the mud, the mesh is displaced & does no good

http://www.concreteconstruction.net/...-floors_2.aspx - good read
thats why Helix is great, used it in my ~900sq.ft 4" thick patio slab, doesnt really matter if they walk in it or not. control joints in right place, etc.

i think OP has it about right. screed it, float it, let dry some before finishing edges or brooming. for a newbie, the last step though requires testing before doing big projects because only experience on how concrete dries will tell you when its ready for trowel and/or broom.

and for those reading this who also saw my other posts about my slab, in ~900sq.ft i think i have only found 3 pieces of Helix that were exposed some.

Last edited by concrete_joe; 02-18-2015 at 05:36 PM.
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