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]

Re: Lightweight Concrete

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

I should imagine it would crumble and fall over.

[david s]

Re: Lightweight Concrete

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]

Re: Lightweight Concrete

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

[brickie in oz]

Re: Lightweight Concrete

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

Out of vermiculite?

[david s]

Re: Lightweight Concrete

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]

Re: Lightweight Concrete

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]

Re: Lightweight Concrete

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

[david s]

Re: Lightweight Concrete

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.