Saturday, December 1, 2012
Timbrel Vaults, mortar material for first layer
I am not an expert on timbrel vaults, but this is what I am doing.
The first layer of thin bricks or tiles on a timbrel vault is laid generally with little or no form work. This makes it cheaper, faster, and xxx than just a brick vault. (It is also stronger)
So what does one use for mortar , a mortar that is quick setting, cheap, and available. It doesn't add any (or much) structural strength to the vault, it is only for holding in place until a complete arch is made. Many arches are side by side the strength is in compression. Well on a timbrel dome it would not be an arch but a horizontal ring being completed then gives the strength, not until last piece is in place.
I use gypsum plaster, or plaster of Paris for "gluing" up the first layer of the timbrel vault. I go buy the gypsum plaster you use to plaster walls in a house. for me it costs $10 a 20kg bag. It is NOT a local material it is imported from Thailand, England , etc
I am not sure what exactly Gaustavino used. The beginner on searches will come up that they used gypsum, but this is gypsum that has been heated to 150C and then ground. this is plaster of Paris. In brief, you heat it up, the water is removed as steam, you grind. When you need it you mix with water 3:1 and it sets within 15 minutes and hard in 30. It has returned to gypsum now. It needs to be kept dry to stay hard.
I just discovered that I should recycle my plaster of Paris .
I use clay/sand mortar to stick up brick on brick vaults. What could I do to make clay work on the same?
What about modern cement additives to make a quick setting plaster?
what about adding some fine sand with gypsum to make it cheaper?
anything else I don't know about.
Next topic: How do you make the tiles stick with gypsum plaster without holding for a long time. Guys in Spain stick them, tap them and they hold. they are adding the next one in less than 30 seconds. I tend to have many rows going , giving the last one a bit of time to dry.