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need advice pouring large slab

Started by OneWithWood, July 16, 2004, 10:38:52 AM

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OneWithWood

I am working my way down my honey-do list of distractions that keep me from working on my saw barn.  The current distraction is the erection of a 30' x 96' greenhouse.  The greenhouse will be heated with radiant in slab heating ala our central boiler unit.  I would like to pour the slab in one continuous pour.  I plan on using 10" tall steel forms for the perimiter.  There will be 4" of #7 crushed limestone packed beneath a layer of 2" foam board.  The 1/2" plex tubing will be attached to the steel mesh and pulled up to be in the middle of the 4" concrete slab.

I have never poured a slab this big in a continuous manner.  I feel I need to pour it all at once because of the tubing running throught the slab.

How do I strike off the concrete?  Are 40' strikers available?  How heavy would one be?  

The surface will not be finished beyond using a bull float after striking.  Is it feasible to push/pull a bull float accross a 30' span?

The cement trucks will not be able to get completely around the perimeter of the slab.  They will only be able to get next to the slab on the east, north and west sides.  I imagine we will have to chute the concrete for about 75' of the southern half using a 16' wooden chute I have constructed and a couple of saw horses.  

I have not assembled a crew yet.  In the past I have enlisted my two female neighbors, my wife and perhaps a male friend or two if they are available. I am thinking the size of this pour is such that I probably should hire some stronger backs. The pros are all booked pretty solid around here so I don't think I will be able to find any esperienced hands.

I sure could use some advice from those who have experience with this size of a pour.

One With Wood
LT40HDG25, Woodmizer DH4000 Kiln

iain

go for 4" of  foam and pull it up around the edges 2" is no where near enough for that size of green house unless your heating is free and plentyfull
then get some real GOOD help with your pour even if you have to wait a few weeks
you maybe able to hire a vibrating screed that wide but the form work will have to be solid
i would break up the pour and at the breaks fit expansion joints 6 panels should be more do-able with your available labour :)   iain

etat

Best advice I would know of is when you assemble your crew make sure at least one of them is reliable, and has had experience with finishing something this large. When you find him tell him you need some of his friends too, lots of work on something that large, a tremendous amount of work.  Probably would want to pay him more than the other guys. When you order the concrete have them bring out extra chutes that hook to the back of their truck  so they can extend out and pour further.
Old Age and Treachery will outperform Youth and Inexperence. The thing is, getting older is starting to be painful.

GF

I would put in some rebar grade stakes then use a piece of 4" or 6" steel C-Purlin 20' long, and pivot off the grade stakes to outside of the forms, this is going to get you pretty close to level, them you can drive the grade stake down. A trowling machine should know any small humps out, I would recommend a finishing machine with long blades since it will not have a tendency to follow any humps.

I also took an 8'  2x4 and fabricated a metal andle for both hands that come up off the top about a foot or so, this will also allow you to smooth out high and low places, depending on how far the grade stakes are you could use this to level in between.

I definitly would not pour if the weather was even close to being hot, it also helps if the slump is wet and pretty much self levels on something this large.

Just my thoughts.

Bro. Noble

We have poured several different slabs around the dairy over the years.  We tried to do all of it ourselves and have learned some stuff the hard way.  Using a board to strike off concrete gets really difficult when you get over 8 or 10 feet wide------use a method like GF suggests.  The guy delivering the concrete can be very helpful and make the job much easier if he is experienced and wants to.  Some drivers cause you about 10 times the work------try to get a driver or drivers that are known to be good.  We once poured a 'tip up'  bunker silo and hired a retired concrete man to help us especially with the 'how to' part.  Best money we ever spent.
milking and logging and sawing and milking

Furby

If you want to do it in sections, just lay out the tubing to fit the sections. Then you can shut off every other section or whatever you need to help control the heating. I belive there is something that you will put down with the tubing to cross the joints for the feed and return lines. If you use joints, I do belive you need to keep the tubing layout within the section, except for the feed and return line.

This is just what is coming back to me from what I have read, so it may not be 100% correct.  ::)

Larry




30' X 50' pour.  The truck could get to all 4 sides.  We set it up for 4 men to do the pour, 2 to strike it off and 1 to finish.  Only 3 showed but it worked out fine.

On that big of pour I would get a good pro involved and let him call the shots.

I really like October and November in this part of the country to pour.  Shorter days, more rain, and less heat in the middle of the day.

Concrete is guaranteed to get hard and .... crack!!  Good luck. :)
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

Stump Jumper

you might want retarder put in the mix if its a hot sunny day
Jeff
May God Bless.
WM LT 40 SuperHDD42 HP Kubota walk & ride, WM Edger, JD Skidsteer 250, Farmi winch, Bri-Mar Dump Box Trailer, Black Powder

Bruce_A

Concrete doesn't have to be a tough job. Just don't try to do too big at one time.  Renting a pump truck is also a good idea.  He can set up and reach all corners from one spot.  Split your pour to three runs length wise, get three or four young hands to pull the screed and pour as dry a mix as possible.  The more water you add to concrete, the more shrinkage and cracking you have.  Rent  a rollerbug when you get a bull float, the handle will fit either as well as a fresno if you want a smooth finish.  Also a good concrete rake will make a lot of difference.  My experience comes as concrete form setter, builder, designer and supervisor on bridges, banks, docks, dams,and generating plants as a union carpenter over the last 35 years when I find I cant make enough money working for myself.  Good luck .    Bruce A

GF

You can also put a 2X4 or 2X6 down the center of the length to strike off fronm the side to the center, once you do bot side pull the board and shovel a little cement in the area it was out, I have also seen people leave the 2X in there for expansion I would treated if you plan on leaving it.

Haytrader

I weld 3" peices of 1 1/2" angle iron on rods about a foot long and drive them in the ground every so often and lay a peice of 1 1/4" pipe in the V. Have the pipe rest on at least 3 of the supports at a time. As you pour, twist the pipe with your hand and slide it to the next support. Take a shovel and put a little extra mud where the pipe was. Just leave the iron in the mud. This does not interfere with remesh.

On a 30' x 50' you would have two rows of pipe and have three 10' screeds.
Haytrader

Egon

For that size think real hard about a contractor. Any little error at the begining can really cause trouble later on as the workers tire. And if the workers are not experienced they will tire.

Egon

OneWithWood

I will be talking with a contractor this weekend.  The rough estimate he gave me just to handle the pour and minimal finishing will break my budget big time.

So, I am still considering the do-it-myself with help option.  

Buce and Haytrader I think I understand how to break the pour up into smaller more manageable sections. Thanks for that advice.  Haytrader, your suggestion of using the pipe is right on target given that I will have PEX tubing running everywhere and could not break up the area with solid forms.
When splitting the area into thirds using the pipes I assume you would pour and screed the outer sections close to the length of the pipe and them come back and do the center.  Move the pipes and repeat.  Is that right?
One With Wood
LT40HDG25, Woodmizer DH4000 Kiln

Haytrader

OWW,

Without looking back, if I remember right you said the cement trucks can't reach all sides. So, you need a pump truck or do it the way us poor folks have done and that is to wheel barrow it. I would probably pour all three sections at a time so you only move the pipes one time. It would be hard to get them in the "V" the second time. There would be a small rock or other variables. You could do maybe 5 running feet in each section at a time till you got close to the end of the pipes and then move them to the next set of rods.

I think someone mentioned a screed board with handlebars. I have made several. What worked best for me was a double 2x4 with "T" handles (about waist high) on both ends. About two feet from each end put an eye bolt in the 2x4s and attach a rope to each eye bolt. If you have enough help, put a guy on each rope to pull the board so the handle bar guys just have to push-pull. If you are short on help, a 4 wheeler or even a hydrostatic drive lawnmower will work.

I will also agree with the ones that promote the idea of professional help or at least get some guys with experience. Remember, you only get one chance at a good pour. Most of mine have turned out well but there were a few that didn't.

We have poured lots and lots of cement aprons for feed bunks in feed lots. They are either 10' or 12' wide and some have gone up to 2500'. When we got the hydraulic driven roller screed, we thought we had died and gone to heaven.
 ;)
Haytrader

bennelson

YOu might want to just stop by a job site in your area.  Most construction guys do sidework.  Offer them cash and most of the time they will jump at the option.  

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