Concrete Slab How To Part 4

Hi, I'm Tim Carter from AsktheBuilder.com and I want to show you, as they continue to pour the slab, an important thing. Look at this. The entire half of the slab is now screeded. But in one corner there is not concrete. Why do you think there isn't any concrete there?

The reason why is the last thing you want to do is to put too much concrete in the area or hole. If you do, you will have to shovel the excess concrete out of the slab. But if you take your time and work with the truck driver, you can make sure that there is just enough concrete down where it is needed. In this case, they are now filling in the last section.

Keep in mind, you are going to work hard enough as it is putting the concrete down. You don't need to be shoveling extra concrete out of the hole. So screed as you go to be sure there is just enough concrete in the area. It's as simple as that.

This is the fourth of four parts on How to Pour a Concrete Slab. Click here to watch Part 1.

Concrete Slab How To Part 3

Hi, I'm Tim Carter from AsktheBuilder.com and we are here continuing to pour the concrete slab. I want to show you a neat tool they are getting ready to use. It's a power screed. It's really, really cool.

It has a small gasoline engine on it. That gas engine causes, through a cable, a vibration in the long blade of the screed. In this example, the workers have created two spots that they are screeding against. You will notice a spot right along the wall and the other spot in the middle of the slab.

They start at the wall and move the screed towards the center. This floats the surface of the freshly poured concrete. The operator just gently pulls the screed along the concrete, but the surface is smooth after the screed passes over it.

With a nice long pull, the powered-screed smooths a wide section of the slab. This keeps the scab surface in the same plane. You can definitely see the difference between the screeded section and the untreated areas. In the old days, it would take lots of time to float that much area.

That is a nice powered-screed. I doubt you will have one on your do-it-yourself job, but hopefully if you use professionals, they will have one. It is a great tool to do a lot of work in a small amount of time.

This is the third of four parts on How to Pour a Concrete Slab. Click here to watch Part 4.

Hi, I'm Tim Carter from AsktheBuilder.com and I want to show you a concrete finisher using a magnesium float to float the edge of some freshly placed concrete. Watch this.

That's how you would use a magnesium float when you are doing concrete work. Did you notice what he did? He puddled the concrete by pushing it up and down. Followed by some real nice gentle strokes to make sure the float stays along the chalk line that is on the foundation wall. That is a nice trick to keep the concrete level. The concrete at this point is very fluid, making it easy to use the float on it right now.

This is the second of four parts on How to Pour a Concrete Slab. Click here to watch Part 3.

Concrete Slab How To Part 1 Video

Hi, I'm Tim Carter from AsktheBuilder.com and we're getting ready to pour the concrete slab. The truck's here. Check this out!

What's really nice about these front-loader trucks is that the driver is in the cab and he can see exactly what the two workers are getting ready to do. By the driver moving the chute back and forth, he can make their work a whole lot easier.

Watch this. Here comes the concrete. Notice that the workers are using the hooks on the end of the come-alongs to pull the wire mesh up into the middle of the concrete.

Look how fluid that concrete is. It is flowing on its own. You can see how you can use the concrete rakes to just pull the concrete. If the concrete is the right consistency, it just flows. The concrete rakes are sometimes called come-alongs, but they look like a regular rake. They just move the material around to fill all the areas.

What's really important to note is that the concrete driver has stopped the flow of concrete while he lets the men work and place the concrete in the corner. Just a nice controlled work flow between the driver and the workers. Don't let the truck driver get in front of you. Tell him to stop the concrete flow if he is pouring too much, too fast.

This is just the first of four parts on How to Pour a Concrete Slab. Click here to watch Part 2.

Hi, I'm Tim Carter from AsktheBuilder.com and I'm here on a job site where they are pouring a concrete slab. I want to show you something a lot of people don't get to see. It is really, really important to know because this is where a lot of concrete fails.

It is called concrete bleed water. Look at this. You can see the shine on the concrete. (This example is very light. Bleed water can be much worse than what appears on this job site. It can be large beads of water on the surface.)

What you are seeing is a really thin sheet of water up on top of the concrete. Now, what is that all about? Let's think about it for a second. What's the four ingredients that concrete is made out of? They are gravel, sand, Portland cement and what? Water.

Water is the lightest component of concrete. If you pour all the other ingredients into a bucket of water, they sink to the bottom. So concrete right after it is bull floated or screeded has the water come to the top. You have to make sure you don't float it into the concrete. It will go away on its own. But if you float it in, it will dissolve the cement paste at the top of the slab and it will make the upper part of the concrete very weak. That is one of the causes of spalling. So don't trowel bleed water back into your concrete slab.

Hi, I'm Tim Carter from AsktheBuilder.com and I am here on the job site today. It is real pretty cool as they are getting ready to pour a concrete garage slab in just a minute.

But first I want to show you one part of the slab that is really important and it is something you might forget if you are doing some concrete work. Look at this. What you are seeing is a big black sheet of plastic. This goes underneath the entire slab, it's thin and it goes everywhere. The purpose of this vapor barrier is simple. It stops the water vapor from the soil from coming up through the concrete. It might be hard to believe but water vapor goes right through the concrete and it will make the inside of the garage damp if you don't have it.

Make sure you have a good vapor barrier under your concrete slabs.

Concrete Wire Mesh

Hi, I'm Tim Carter from AsktheBuilder.com. Guess what? They're getting ready to pour a concrete slab today. The concrete truck is on the way. What I want to show you is some wire mesh or steel reinforcing that's put in concrete. It is very important. Look at this!

What you see is a piece of wire mesh that is 6 inches x 6 inches. It is what is called 21 pound mesh. It is pretty light weigh and the best part about this particular mesh is it comes in flat sheets. Typically, it is purchased in rolls, but I don't recommend it as it is very hard to unroll it and get it to lay flat.

What the concrete men can do it tie it together if they want. But as the concrete is being poured, they will pull up the mesh and get it in the center of the concrete slab. The importance of the steel mesh is concrete has great compressive strength, meaning you can squeeze it and it won't fail. But it only has one-tenth the strength when you pull it apart or try to bend it, as compared to compressing it. But steel on the other hand has tremendous tensile strength, so it takes a lot to pull the steel apart.

So putting steel in concrete, you make it much, much stronger. It's that simple. Make sure you have reinforcing steel in your concrete.