Doing the mud for Catalan vaults, why they don't fall

What I get asked a lot are the mix proportions Did the mix? Does the proportion of the mix? Well, lump of lime (25 kilos), depending on the sand, the thickness of the sand, because there are very thin sand he puts four to five cans(20 liters), to a package of lime (25 kilos). when the sand is a bit thick because it will lay three depending on the consistency you will want to give the mixture and to ... one sack of cement (50 kilos) is put four lumps, four lumps of lime (25 kilos each) and already multiplied by the portion of sand That is the amount that is put into the mix and get it anywhere lime, cement wherever it gets. There is not a very special mix many people ask or say that put sealant or that put resin to hold it, right? The explanation of this material is still damp, absorbs moisture, so it is that stops; but if they wet paste, does not stop. Then the brick is dry? The brick is dry. Yes, if you put the brick wet it will fall, it does not absorb anything, and, as it comes down. And another good explanation ... very logic of the dome: Do not fall for that has been in a curve, an arc. Is an arc, if I lose around the bow, I come down; but while you have around, not fall Whether with little curve it takes, holds.