Wednesday, November 25, 2009

Walls of foam Lego blocks

I went out to the property to see what they were up to today. They were building walls of foam.

Getting another form to add to the wall.

These are the forms for the concrete. They are made from expanded polystyrene foam (similar to what is used in a foam coffee cup) and high density polypropylene. On the top and bottom of each form, there are plugs and sockets, sort of like Lego blocks. When they stack the blocks, these plugs and sockets get connected together and hold the forms in place with respect to one another. There are pieces of high density polypropylene that connect the two sides of the form together. These ties, will be embedded in the concrete, and also hold the steel that will reinforce the wall. Right now, we are just getting the first couple of layers put up, so that the bottom of the walls can be poured at the same time that the floor is. The means we don't have to set up forms just for the floor, and then build the walls around the floor.

 Here another form is being readied.

They actually come folded up, and they unfold them, and then stack them.

When they get to the center of the wall, they have to cut the forms to fit in. Here they are measuring.

Since the forms are made of foam and plastic, they can just cut them with a hand saw. They measure, then they trim the form to fit in.

 Here the layers for this wall have been put in place, and they are just adding the re-bar to the last form.

I took one of the pieces they trimmed off, so that I could get some better pictures to show what the forms are like. Each wall form comes as a 1 1/2 foot tall by 8 foot long block. For my walls, they unfold to be about 13 inches thick.

This is the form folded up.

The black piece of plastic that is running from the left middle, to the bottom center, is embedded in the foam. It actually serves as an anchor point for wall finishes on the inside and the outside of the wall. They will be able to drive screws into the plastic, and it will hold them. To find where these anchors are embedded in the foam once the wall is done, they look for the squiggly lines on the face of the foam. You can see them on the foam that is on top, in the above image. The ties that run through the concrete, are hinged on the pieces that are embedded in the foam, so the whole form can fold up to take up less space on a truck.

Here it is unfolded.

With these forms unfolded, the foam sides are 8 inches apart, for making an 8 inch thick concrete wall. You can also see how the foam has the plugs and sockets on the top edge (there are matching plugs and sockets on the bottom), which would connect to a form placed on top of this one. They also put teeth or grooves into the inside surface of the foam, so that it will hold tightly to the concrete. You can see the jagged edge on the inside of the form. The concrete will fill these in, and lock the foam to the surface of the concrete. So it is joined to the concrete with the ties, and in between the ties, the surface is firmly attached to the surface of the concrete as well.

 Here is a better look at the ties that will be embedded in the concrete.

Above, you saw where they were adding the rebar to the forms. To have it located in the correct place, they put it into the rounded slots you see in the ties. As they go up, on each layer, they shift the rebar from one set of slots to another. Then when they put in the vertical rebar, it will slide down between the rows of rebar they layed in horizontally, and it will end up being like a woven mesh of steel. They also layed a wire mesh in to the tops of the forms. I don't have a good picture of it, but it looks like a row of wire squares. This should make one heck of a strong wall!

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