Pouring concrete floor, HF mixers

[Proctologically Violated©®]

Awl--

I'm getting ready to pour a floor, which has to be done in sections of about

2.5 feet by 14 feet, by about 4 to 6" deep--or about 1/2 to 2/3 of a cubic yard at a time. Cupla Q's:

Any experience with HF mixers? They have 1.5, 2.5, 3.5 cu ft mixers. I've rented a 2.5 cu ft mixer, which seemed convenient ito # bags of ready mix one could put in it--but don't quite recall all the details--it was a pretty traumatic experience. For some reason, some of the HF 1.5 cu ft mixers are more expensive than the larger ones. Why would that be? Same HF mfr--Central Machinery.

Should I use wire or rebar? What size rebar? I plan on using QuickCrete mix, or the equivalent. Any tips? Should I break up the pour into, say, 2.5 by 3.5 foot sections, or just a continuous 2.5 by 14 ft pour? If smaller sections, is 3/4 pine OK for the joints? Lay down plastic sheeting first? Any kind in particular?

Not a critical pour (shop floor), but don't want to screw things up unncecessarily, either.

Would like a demo on getting a smooth floor. Any advice or mebbe a dvd on this I could buy? Mebbe Sakrete puts one out. Or Jimmy Hoffa?

TIA. Appreciate all input.

-- Mr. P.V.'d formerly Droll Troll

[nailshooter41]

I am just wondering... why does it need to be in so many pieces? The more sections you pour (especially the smaller ones you describe) the more cold joints you will have, the more movement you will have, and the harder your floor will be to finish.

You shop floor should be burned smooth with a troweling machine so that you can easily sweep away all the dust and debris you will generate. With all those cold joints, your floor will be rough, your machines will not roll, when the floor heaves due to climatic conditions your floor will be uneven and if all sections are not properly doweled to together, they will separate with wild abandon.

This is you shop; take the money you are spending on the mixer and concrete, and pour it in one piece if you can. Your expansion joints should be cut into the new floor with a walk behind concrete saw (easily rented) about an inch deep to divide it into sections that will move with the substrate.

When I was pouring tilt panels and lots of concrete all the time, we cut our panels with the walk behind saw the day after pouring so the concrete was still really green and easy to cut.

Robert

[buffalobill]

we tried doing an outside pour with truck delivered mix in sections and in a hurry found out how stupid we were not to get a loan and bids with a concrete contractor. we wound up short handed, sucked at finishing the surface, and all our work was a waste of time and had to be torn out.

[hallerb]

with such a large amount of concrete needed the cost of sakrete will eat you alive... really compare the cost of 5 yards truck delievered and 5 yards of bags. sakrete will likey be 5 times the cost.

you will get a better job and near the same price and a ton less work by having it done professionally.

because sakrete or buying concrete materials sand cement gravel costs so much more than delivery by concrete truck

[marson]

i once poured a 30X40 slab (in four sections) with a 1/4 yard mixer. i had a large crew. never again! the batches are inconsistent and the time lag between the first and the last made finishing a nightmare.

even with ready mix, there are many ways for a beginner to screw up a slab finish. mixing small batches will make it even tougher.

I'd use rebar just because it's cheap insurance IMO, though probably not necessary. you can also use fiber mesh to control cracking.

whether you use plastic (6 mil black) under the slab depends. don't need it for a garage. definitely in a house. i'd strongly consider using foam instead of plastic. don't think you need anything in your joints. you only need expansion joint material where a slab is butting into something you don't want to move, like a foundation.

as for finishing techniques, you can google finishing concrete and find some info. make sure you have the right tools. you can't float with a steel trowel and you can't trowel with a float. again, if there is any way to pour it all at once do it. and rent a power trowel.

[George E. Cawthon]

I helped my dad pour a lot of concrete, concrete walls, and we used a 3 or 4 cubic foot mixer. I wouldn't want to use anything less than 3-4 cF for the amount you are pouring. It makes no sense to use ready mix when you are mixing it; the cost will be enormous. You need to buy a gravel-sand mix (often called road mix) and cement. Count the shovels of road mix, count the shovels of cement, count the gallons of water.

Two people work fairly well, one mixing, one placing the concrete when putting it in wall forms. If you have it pretty well set up, the stuff will be just about done mixing when the wheelbarrow gets back. You probably want 3 or 4 people for doing a floor. You are only talking

3-5 loads assuming 3 cf mixer and wheelbarrow; so thats probably 20-40 minutes of mixing.

As to the questions, you need a book to look at for how to prepare for the floor, using wire, screeding, etc.

[hallerb]

you know building all the forms and getting them just right will be a ton of additional work.

at least get a estimate for a concrete truck as well as a finished estimate along with the cost of sakrete for comparison purposes

at least that way you can make a informed decision

[Edwin Pawlowski]

Keep in mind also, it is tough work. If you drive a desk all day, it may be beyond your physical capability.

>

[DanG]

As others have said, I think you should hire the work done as you don't know how and some of your questions indicate you have little experience. That said, we all started somewhere. Errors in concrete are harder to erase than some other materials.

Concrete likes to be square. Concrete never likes to be larger than 12 feet. You are considering some long skinny rectangles that do not lend themselves to concrete. Can you make the sections 7x7 or 3.5x3.5? 7x7x4" would be just over a 1/2 cubic yard per section. Most sack concrete is 2500# on its best day. This mix is difficult for professionals to get a slick hard floor. If you pursue this course, either get the sack concrete with more portland in it or add your own. Be very careful about the size of sacked concrete you purchase. 1 (one) cubic foot of concrete weighs 140-155 pounds depending on several variables. Some sacks are 40 #, 60#, 80#. Plan on an 80# bag to make about a 1/2 cubic foot, about 30 bags for a 7x7 with very accurate sub grade.

Wire mesh holds the cracked pieces together after they crack, it is not a reinforcement. Rebar is a marginal reinforcement when used in a 4" slab as you don't have much concrete cover over the bar, but you could use #3 bar on 16 to 24 in centers. Make sure you position the rebar at or slightly below center of slab as you are trying to reinforce the concrete in tension.

You've not said if this is in an existing space or a new slab for a shop. You've made no mention of footing or thickened edge, so I assume it must be existing space. No code authority would allow you to build it without a footing. Either way, I would put a vapor barrier under the slab. For your purposes 6 mil visqueen should be adequate. What kind of shop? ______________________________ Keep the whole world singing . . . . DanG (remove the sevens) [e-mail]