Sunday, September 09, 2007

Second Time Around

OK! We are set up to pour again Monday morning about 10:30 a.m. so keep your fingers crossed for me. I wish we could have gotten mud earlier but that was the best we could do; I just hope we have enough daylight to get a good slick finish on the slab. I could not arrange a finisher either so looks like me and Allen are going to be pulling double duty. I told him if he would run the troweling machine, I would be the one to get down on my knees and do the hand work. I was able to get everything back together and ready on Saturday so I had Sunday free to work on the inside. I mucked out all the soft stuff and put the plastic sheeting back down. You need to do this anytime you have a slab that is going to be in an enclosed area or you will have moisture wick it's way up through the slab and make the concrete sweat. That causes all kinds of problems. Always use at least 6 mil poly too for this. My rebar is laid out on a 2'x2' grid; all #4 bars. You could use that welded wire that has the 6"x6" grid but I had salvaged this rebar; it's easy to come by. You must put something in your slab though. What most people don't realize is that concrete is going to crack. I don't care what people tell you; it's going to crack and if there is not some kind of reinforcing in the slab, pieces can begin to float up or down and then you've got a mess.
This is the western edge of the slab that will one day (when the other half of the house is built) have a door here. There will be a block wall laid on this edge and since I don't have a footing for that, pouring this edge thick will take care of that. That is a 6" edge form there made of 2x4's ( the slab itself is 4") and we dug out from that form about 8-10" to form a horizontal flat area that slopes up to the normal 4". There are steel drive pins about every 4' behind the edge form to hold in but so much dirt washed behind it also, that thing ain't going anywhere.
We determined the top grade of the slab by measuring down off the bottom of the floor joints. The house is level (yea!) so this should give us a consistent measurement. We drove these rebar pins (at grade) about every 10 feet to give us something to screed to on the dirt bank side. On the concrete block side we just popped a chalk line.
I had to scrap in the rebar since it obviously was not made to order, so that means lots of filling in places and laps. Lap your rebar at least 16". I saved all of the drop from when Charles laid the concrete block and made all those cuts and that is what I am going to use to chair the rebar up with. Works great. Rocks work great too if you don't have anything else. The rebar should sit about in the center of the slab. It's best to leave the rebar laying on the ground and just have the little blocks nearby so you can roll a wheelbarrow over the steel, if you are going to have to do that and I think we will have to wheel just a little of this. The slab is just about 13'x 36' and 4" thick so that's about 5.75 yards of concrete. Hmmm, Allen said he just ordered 5 yards. Going to have to see what size he figured. Do you know how to figure concrete? It's not hard but you have to know how to convert inches to decimals for the slab thickness. Anyway, 5 yards is a piece of cake. The biggest pour I was ever on was only 700 yards. That's 70 full concrete trucks minimum. We worked 16 hours straight that day. Allen has poured upwards of 1,200 yards at one time, I think, when he worked on a cement factory.
There is something always kind of exciting about pouring concrete. On days of a big pour, most of the guys are always in a good, festive mood. I'm not sure why. It's almost like the same kind of excitement I feel when I am firing a big load of pottery. I think it's because you have spent all this time building these forms ( like giant molds) which can sometimes take weeks, and when you pour it's like you are casting your piece of art. We sometimes even have a special lunch or something if a big pour comes off well.
I'll try to have photos soon of the finished slab.

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