Heat stop premixed mortar

[Scope1]

Re: Heat stop premixed mortar

Just got Heat Stop 50 upstate NY at Herringtons in Hudson NY for $55 a bag, fireclay was $27 for a 50 lb bag. They also have red firebrick at $1.80 each. At that price for HS 50 its hard to justify making your own mix .

[NCMan]

Re: Heat stop premixed mortar

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.

Thanks. I think I'll be going w/the 8:1 mix, then.

[NCMan]

Re: Heat stop premixed mortar

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

If you notice, I'm a big fan of leaving forms on. I never take them off until they have to come off. The longer they stay on, the better. Thanks.

[stonecutter]

Re: Heat stop premixed mortar

I looked at some notes I had on my oven in CT.....8:1 on the insulating slab.

[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.

[stonecutter]

Re: Heat stop premixed mortar

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

[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

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

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

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

[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

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

[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?

[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.

[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