Vermiculite cure time. Newbie Forum Discuss Vermiculite cure time. in the Good Background Information forums; Hi all, Rookie builder here. I have just finished the vermiculite pour of my hearth, and I was wondering if ...

[JAG]

Hi all,

Rookie builder here. I have just finished the vermiculite pour of my hearth, and I was wondering if someone could tell me what kind of cure time I can expect, also is there any needed curing of the vermic. layer as there was with the concrete layer?

Thanks,
John

[asudavew]

If it feels hard and setup.. you are fine to start building your dome.

Mine was pretty hard the next day.

[gjbingham]

I just poured mine yesterday morning. It was pretty well set by early evening. It's definitely hard this morning.

[Frances]

Well, mine took about a week to get hard, and continued getting still harder for a week after that. I think I'd recommend waiting for a week before starting the dome - its the cement component which hardens after all, and that just needs some time.

However, I remember reading a thread recently (wish I'd read it when I was at that stage) which says you shouldn't cover the vermiculite layer like you do cement, because it already absorbs so much water while mixing.

Hope that helps...
Frances

[Neil2]

This is a type of concrete. The portland cement in the mix will need water to cure. Keep it covered and wet for at leat a week minimum. Three weeks would be better.

I would say you could start building the dome about 3 days after the pour.

[joninaz]

Along the same lines, is it better to cure when it's warm/hot or cold out? For example, I'm in AZ and am concerned about curing "too fast" in our very hot summers.

[dmun]

I think fourty degrees F. is the magic number. Below that temperature the concrete weakens considerably. It's also hard to work with wet heavy stuff when it's cold.