48 inch forest of dean UK

[brickie in oz]

Cant help there sorry as I have no idea what the stuff in the bag is.

[Denden]

Hi there I used the same "air setting cement" from kiln linings and it worked fine. Dryed pretty quick as well, I did build mine in the middle of summer though, maybe the damp winter air is not helping. I maybe wrong though.

[smallholder123]

No not at all wrong there we have noticed a big chang in the setting with a few dry warm days all is going well will finish the top of the dome this week

[Amac]

Hi smallholder123
Initially I bought 3 25kg tubs of airset cement. It was rather expensive and if you look at the FB recommendations on some sticky or other they are very specific that you should not use airset cement. I rang the manufacturers and questioned them about it. They said it wasn't suitable for joints >3mm (I think). That decided me since my joints are tapered from up to an inch to zero. I returned them all unopened and they refunded me. I decided to go for what is usually referred to as "homebrew" on this forum i.e 3 sand 1 portland: 1 lime : 1 fireclay: and I have almost finished building the dome with that. It is much much cheaper.

I think you said your arch was exposed to rain? I think airset is not meant to be used outdoors. You might get away with it if it is kept covered - but I recommend you change it for the homebrew or a dry premix (add water).