Chapters from this episode
Now Playing
Clip Transcript For:
Constructing Concrete Walkway with Crushed Granite Aggregate
computer-generated transcript - may not be 100% accurate
" You guys pour a specialized concrete here, right?"
" Yes, we do."
" Let's talk about the prep work first. I noticed you've got the shape all in place, and of course, that was designed by our landscape architect so that it kind of winds its way to the front door. What is the frame made of?"
" The frame is made out of a 1 x 4."
" 1 x 4, so that means the thickness of the slab will only be 4 inches, right?"
" 4 to 412 inches, yes."
" Now, do you need to put down a plastic vapor barrier like you're using here in an exterior situation?"
" No, we don't Bob. It's not a plastic vapor barrier. What it's for is it is about to control the water in the concrete to hold it in a lot longer to make it stronger."
" I see. So the concrete will cure more slowly and that's how you get a stronger in the slab."
" Yes."
" Yeah. But the main thing in the slab is all these reinforcing that goes in here, right?"
" Yes. You have to have that type of furnace."
" And this is really very stiff stuff. It looks like, almost like reinforcing rod as opposed to the wire reinforcing the top and put into a sidewalk."
" Exactly."
" So I guess this has the float in the middle of the slab, right?"
" Right."
" Good."
" As before, we'll be checking that up."
" Yeah. And you got your level line in place right here."
" Yup."
" Okay. So what about the concrete itself? The truck is here. Is there anything special about the concrete? "
" No. it's just 3,000 pounds of concrete. "
" 3,000 pound mix."
" Mix, yes."
" And, then the special feature comes in in the finishing, right?"
" That's right."
" When we'll be putting in some of these aggregate right on the top."
" Right."
" This is----"
" Right after we top form."
" Okay. Well, let's her rip and get some of that concrete in here, huh. There is it. And we're using maybe 2 yards here."
" I'd say a little more, probably 312."
" It's hard to pinpoint precisely how much you're gonna need for a walkway like this."
" Exactly. It all depends upon the gap."
" Yes."
" As you can see Bob, [unk] why it mess up."
" Yeah, that's the important thing to keep in mind is the cement wants to be centered. If your slab is 4 inches thick, that mesh or reinforcing rod really should be up to it."
" Exactly. You know, it doesn't serve any purpose on the ground."
" Exactly."
" Hey Bob, here it is screed in the concrete. "
" Screeding, which is the----"
" Creating a level on it."
" word that means leveling it off, yeah. And over here, he's got a different kind of tool. What do you call that?"
" That is a bull float."
" That's right. A bull float. And, that eventually is the first swipe that you make on it to start smoothing it out, right?"
" Exactly. As you noticed Bob, this is a special bull float. It's a ribbed bull float. As you see, the lines [unk] not tight."
" Yeah."
" It's not. What it does is that helps push the stone down to bring some of the frame up that was underneath to bury the aggregate stones."
" Okay. So this is the first specialized tool that we're using."
" Exactly."
" And the objective is to try to bring some of the pure cement,----"
" Cement on top."
" pure Portland up without any aggregate in it."
" Exactly."
" Now this is a custom job that will end up looking a little bit like natural granite. What is this material that he's casting here?"
" This here is a colorant Bob that will be put on over the concrete and buried in, and what it does is that it gives it color to the concrete. "
" So, it looks kind of blue-gray."
" Yes, it is."
" And is it a ground up stone or what?"
" No, it's just a dye."
" It's a dye."
" Simply dye."
" Yeah. Well normally, the concrete would dry out to a kind of gray, gray-white."
" Gray-white, yeah. This white here is gonna have a granite look to it."
" More of a blue, yeah."
" As you can see, once the colorant is spread, it turns like a water-based, and what it does is it spreads across the whole top of the concrete. "
" Well, you really start to see the difference now between that last square that's still the normal concrete, you see the olive green there, and the rest of it where you put in this colorant or pigments."
" That's right, Bob."
" Yeah. Now, the aggregate that goes on top is simply crushed granite, right?"
" That's right, Bob."
" And this can just be scattered along the top or do you put a lot of it on it?"
" I put a lot, Bob."
" Lots of it?"
" Yeah. To get an even broadcast all the way across."
" Nice action with the shovel there, yeah. Because the idea is not to throw big bunches of it, but to cache it evenly."
" Yeah. Evenly is the correct word."
" Yeah, I notice how he handles that shovel. He lets it all come up the side of the shovel and it's in the wrist----"
" That's all there."
" the way he's getting it to fly out of there. So now, another pass with the bull float. What's that accomplishing?"
" Okay, what he's gonna do is bury the stone so that you can't see it anymore."
" Really?"
" Yup."
" Well, I thought the whole point was to see the stones?"
" Well, we'll bring it back up later."
" Now this is pretty counterintuitive though. I mean you want to look at exposed aggregate and you're burying it off. Why?"
" Well, we're burying it so that we get the concrete all around the stones so we don't have any problems with the stones coming up."
" Alright, we've let 4 hours go by in real time, and that's enough to let the concrete set up so that that Portland cement is almost like cream at the top of the bottom and you can just wash it off now."