Thursday, November 18, 2010

Pouring the slab

Poured the concrete slab today.  Notice in this first picture that the tubing is arranged in smaller loops with a space between them.  that's for different zones, and to allow the concrete expansion joints to go in without having a tube cross it.  An expansion joint is a pre-planned crack, that allows the slab to expand and contract.  Having a small joint there keeps the rest of the slab crack-free. 

Notice the orange line in the picture above- that's the target concrete level.  After the concrete is poured in, it's screed.  This is done by drawing a straight edge along the top of the concrete to cut off the humps and fill in the hollows.  it gives you a roughly level surface.  In the picture below, they're using the painted line on the sidewall to guide their scree.   

 Once screed, the concrete looks level in this picture, but there's still some ridges and hollows.  The next step is to go around the edge and hand-trowel the 12" in on all sides.  the picture below is the screed concrete. 
 The next step is to bull float the concrete.  This tool pushes the rocks down into the concrete and makes for a smoother surface.  you'll notice that it's a little shiny; the "cream" comes up out of the concrete, and this is what will eventually form the shiny finish on this floor.  I prefer a smooth, shiny finish for surfaces that I'll be pressure washing.  A rougher surface allows better traction, but also means that stuff sticks to it better and it's harder to clean. 
 In the picture below you can see the difference between bull-floated and screed surface.  The top right is the screed, the area to the left of the bull float is floated.
 Now we've bull-floated the entire surface and it's roughly level -- level enough for a barn.  We poured at 8am, and we were here at about 10:30-11.  Now we wait an hour or two for the concrete to firm up a little.  The plant added a lot of water to the mix, and that makes it easier to get out of the truck, but it takes longer to get to the consistency you need to use a power trowel. 
 The power trowel is how you get the smooth, shiny surface with the least amount of effort.  This tool has 4 blades that rest flat on the concrete and weighs about 300lbs.  You use it like you would a floor polisher, and in effect that's what it is.  If there are any dips or rises, this tool will help to smooth them out.  It will also push the rocks a little deeper, and bring up more cream. 
 Probably 2 hours of power trowel, and then some hand work, and then we enclosed the whole slab in plastic and installed a small propane heater to keep the air warm.  It'll be cool tonight and we don't want the concrete to freeze.  Concrete does generate some heat as it cures, but the propane heat means and we don't  take any chances. 
Slab is in, smooth. level, and warm.  A good day.


Anonymous said...

Did you sketch in the year and your name in the concrete?

Joanne Rigutto said...

Great tutorial Bruce!
I've worked in construction since 1985, with this year being the first year since then that I hadn't because I was farming full time. This was a nice trip down memory lane, even though I speciallized in the tile and stone trades.

Also an excellent documentary of how concrete is poured/finished for those who don't know.

Anonymous said...

I saw the "tent" up last night on my way back to the farm. Looks good! That smooth surface will make cleanup much easier!

Anonymous said...

Nice job Bruce, Do you pour the concrete with the radiant tube pressurized or empty?

Bruce King said...

Poured with the tubing pressurized so that we could make sure that it was good throughout the pour. It's still holding pressure 24 hours after, so I think we're good.

Bruce King said...

That tent will probably blow away tonight; the wind is pretty gusty, but at this point the slab is in good shape, curing nicely. We'll be forming up the wall extensions starting tuesday. Going to go up high enough that the floor will be above the flood elevation so that I can put stuff in there in the event of a flood and have it be safe.