Small arches for support of the big arches ready !

March 15, 2019

Main shape of the form

The last updates on our blog are not really coming through regularly, but believe me that we not been picking our noses here. Just minutes ago I completed the removal of the forms of the small arches. The arches on which the much bigger arches will rest. Normally we remove the forms after one or two days, but this time we let it cure a bit longer in order to reduce the chance of cracks and corner pieces to break off.

How we did it...
We made the form of standard form wood, which is water and concrete repelling - it will not stick to it. Below this we placed numerous stamps. Six below the arch form to support the vertical forces and 8 horizontal to prevent the forces to the inside of the side pillars (see images what I mean with this).

Concrete is heavy, I cannot get used to it.
Better save then sorry. If you make your form to keep the concrete in the shape you want, you need to make it super strong. We needed 3 mixer loads of concrete per arch, which equals 3x300 liter = 900 liter = 2250 kilo. The weight at the bottom is always the highest and if you leave a tiny space somewhere at the lowest point, it can lift the whole form structure with many hundreds of kilos. We have seen this when we created 'The Wall', we couldn't believe it, but rational thinking makes it logical.
This time, everything went according to plan, the result is exactly how we intended it.

Next: creating the big arches, resting on the small arches.
Now the smaller arches are in place we start thinking about the big arches. Three arches in total, covering the extensions for room 1, 2 and 3. These are all resting partly or fully on the small arches we just created.

What's the plan ?
We will use polystyrene for the main shapes of the arches. It's light and it looks soft, but it can carry a lot of weight. Nearby is a company (Polivas), where you can buy big blocks of this material of 400 x 120 x 50 cm each. They can cut/saw it with a hot wire in the shape you want - they have an impressive saw table for this, CNC controlled. For sure we will do it this way; it saves a ton of time and it's super light - although the material is not really cheap.
We have to make the 3 arches in 1 time in order to balance the forces of the concrete to the sides, which means that we need 6 of those giant blocks. On top of the blocks we will place wooden planks, only because the original arches were made the same way. The blocks will rest on standard 3 cm form sheets which will be supported by many stamps.

I can't wait to get started. Next week I will order the polystyrene, cut in the shape I need.
In about 3 weeks time I think we are ready to pour some more concrete.

Thanks Folkert and Peter for your professional advice, which is highly appreciated.

Have a nice weekend !


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