Heat stop premixed mortar

[Gulf]

Re: Heat stop premixed mortar

.....Do you think that the 4" of Perlcrete under the hearth floor is fine? I know more is better, but elevation wise, 4" works.

I think that 4" of perlite (no greater than 5 to 1) will work great! as long as it is allowed to, and and also kept dry .

[NCMan]

Re: Heat stop premixed mortar

Ok, thanks. I was planning on a 4:1 or so and will use a vapor barrier between the slab and it. Also, will do my best to keep it all dry.

[stonecutter]

Re: Heat stop premixed mortar

You can go leaner for a greater insulating value.

[NCMan]

Re: Heat stop premixed mortar

By "leaner", I'm assuming you mean more Portland and less Perlite? Or the other way? I'm not real familiar w/that term, although I've heard it before. Some people use that term differently. Since the Perlite "slab" will be holding up the entire weight of the oven, I want it to be able do so effectively. What ratio are you proposing, just so I understand you correctly? And thanks for helping a greenhorn.

[stonecutter]

Re: Heat stop premixed mortar

By "leaner", I'm assuming you mean more Portland and less Perlite? Or the other way? I'm not real familiar w/that term, although I've heard it before. Some people use that term differently. Since the Perlite "slab" will be holding up the entire weight of the oven, I want it to be able do so effectively. What ratio are you proposing, just so I understand you correctly? And thanks for helping a greenhorn.

A lean mix in masonry refers to less portland or binder to aggregate. Perlite or vermiculite is the aggregate in an insulating mix. I went 5 or 6 :1 on all my builds. Tscar had some kind of compression value chart he posted at one time, I don't have it though. But I'm pretty sure you would be ok at 8:1

[NCMan]

Re: Heat stop premixed mortar

Ok, thanks for the explanation. I'd like to obviously have it be strong enough to hold the weight, but get as much insulation value as I can. I'll go with either 5 or 6 for now. I'll also try and find that info from TScar. I know more is better, but in your personal opinion, is 4" sufficient? That elevation works best for us, but if it makes a huge difference, I could go a bit thicker. Perhaps going leaner helps make up for the thickness, thereby raising the R value (?) So, say if I stuck w/the 4" thickness, but went leaner to say, 5 or 6:1, it makes a good bit of difference, if I follow you right. Makes sense to me. I've never worked w/this material, it's all new to me. I appreciate your info.

[NCMan]

Re: Heat stop premixed mortar

Also, if I remember correctly from earlier reading, the components should be thoroughly dry mixed prior to adding the water, right?

[stonecutter]

Re: Heat stop premixed mortar

That the way it's normally done...avoids the portland getting clumps.

[NCMan]

Re: Heat stop premixed mortar

I would assume that. Everything else I ever mixed was dry mixed. Just wanted to be sure. And try to fold it over when mixing to avoid chopping it all up, right?

[stonecutter]

Re: Heat stop premixed mortar

Yes...........

[NCMan]

Re: Heat stop premixed mortar

Thanks for the help. I will probably get around to getting some Perlite and Portland this week after I raise up the forms. I'm still not sure if I want to go thicker yet. I'll probably stick to 3.5" and mix it at a 5 or 6:1. Once I mix it all up, get it in, etc., is there any advantage to covering it up for awhile,or not? I still have the slab covered (it's still as green as the day it was poured) and will keep the moisture barrier in between the two "slabs".

[stonecutter]

Re: Heat stop premixed mortar

I would only cover for a day or so, then let the sir and sun start working on it.

[NCMan]

Re: Heat stop premixed mortar

Ok. Thanks again. How long, in your opinion, should I allow the Perlite dry and air out before I start building on it? I know temps, etc come into play, but on average, how long is long enough? I'm not in a hurry, just anxious.

[stonecutter]

Re: Heat stop premixed mortar

A week or so. Sooner if you leave the form on.

[GianniFocaccia]

Re: Heat stop premixed mortar

A lean mix in masonry refers to less portland or binder to aggregate. Perlite or vermiculite is the aggregate in an insulating mix. I went 5 or 6 :1 on all my builds. Tscar had some kind of compression value chart he posted at one time, I don't have it though. But I'm pretty sure you would be ok at 8:1

I agree. I went with an 8:1 vermicrete 'slab', mostly because it was right in the middle of the ratios (4:1 - 12:1) reported here. After installing the vermicrete under 2" of CF board, I placed some of the last batch surplus into a round butter container and let it dry (3 days).

Even at 8:1, the test 'disk' (6" diameter by 1" thick) was surprisingly rigid and very difficult to compress with my thumb. It had the consistency of one of those puffed rice crackers. I could break an edge off quite easily, but when I placed an 8x8x16 CMU on top of the disk edgewise, it didn't budge.