Lightweight Concrete

[dmorgs]

I'm thinking of pouring an in place, lightweight concrete chimney (vermeculite). Also, I'm going to apply an insulating coat on my dome with lightweight. The dome is recently finished.
Any of you with experience care to illustrate the difference in the two mixes. I read the section about this on the website but I'm a little confused, hoping to get a more basic understanding.
Thanks, JJ

[brickie in oz]

Originally Posted by dmorgs

I'm thinking of pouring an in place, lightweight concrete chimney (vermeculite).

I should imagine it would crumble and fall over.

[david s]

Vermicrete is not particularly strong and the Portland cement breaks down at around 300C so you are most likely to have a failure.

[Johnny the oven man]

Better of getting an insulating refractory castable, they do make a lightweight 1400c grade material. Not crumbly at all.

[brickie in oz]

Originally Posted by Johnny the oven man

Better of getting an insulating refractory castable, they do make a lightweight 1400c grade material. Not crumbly at all.

Out of vermiculite?

[david s]

Johnny,
I had difficulty finding one. What was offered to me as a lightweight castable was almost as dense as the dense castable I use. What is the density and the name of the product you're suggesting?
Al,
Vermiculite is only good for 1100 C so it must be different aggregates if it's good for 1400C

[Johnny the oven man]

1400c LW is 1050kg/m3, 41% alumina,42% silica,15% cement. I will chase up the content info for you. Product is from Sila. They also make Silalite LW100, which is 1000c rated and is 800kg/m3, this would also do the trick.

[dmorgs]

Okay then, clear enough I guess. What about the mix for the insulating layer?

[david s]

Originally Posted by dmorgs

Okay then, clear enough I guess. What about the mix for the insulating layer?

Vermicrete would be good for the insulating layer it doesn't need to be strong and won't be subjected to high heat.