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.
http://www.artmolds.com/ali/history_plaster.html
http://www.gypsum.co.nz/pages/product/kids.php
http://answers.yahoo.com/question/index?qid=20071207014217AAKIusG
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.
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Very informative Eric. I would think if you are using stone tile/pavers like say, 1 1/4" thick, that you would have to use a form because they are much heavier than brick tile. What do you think?
ReplyDeleteIn ethiopia and somewhere in Europe they used stone tile/pavers and same method. http://sudu1construction.wordpress.com/ although i cant find the place where it says that. I think my brick tile arent much lighter than stone, but more porous. I am not happy with my gypsum mortar yet, others they build much faster. Tap tap tap and they let go.
DeleteHere in New Mexico, USA we use gypsum plaster for interior plaster and we mix it about 3 sand to one gypsum. I prefer a coarse washed sand as it gives it more body for the scratch (1st coat) and the brown coat (2nd coat). You could try some lime in your mix to make it "stickier", but only add it just before use as lime and gypsum have different set times. I look forward to seeing what you find out out. A great topic.
ReplyDeleteWell there you go, some good ideas to try. I will try sand and lime (seperately). I would think i should add lime first as it sets slower. thanks man.
DeleteChes the sand and gypsum plaster works. I tried lime/sand but did not get good results on holding quick, and then later it is not as hard.
DeleteBeen visiting Guastivino built sites in NYC. His tiles are 5/8"-11/16" thick. Regarding plaster of Paris, the plasterer sub contractor I use has a nice technique. As you know, plaster goes off quicker when mixed. When you add water and mix, it quickens the process. He makes a circular dam of plaster and pours enough water in the center to thoroughly moisten it and leaves it. He mixes it with joint compound to speed up dry times. He will go over to the moist plaster and only take what he can use in a few minutes, not disturbing the rest of the moist plaster. I think for setting the tiles the thoroughly moist plaster would be more adhesive than a batch mixed and used quickly. If that makes any sense.
ReplyDeleteAndy- thanks. find my email on profile. does he then add more water before using. what is "joint compound".
Deletei will try the method your plasterer uses.
Try putting some up. Other experiences would be great.