Curing

[Neil2]

Re: Curing

Portland based concretes must be cured with continuous moisture to reach useful strength. Typically 7 days minimum.

[Paul in Rockwall TX]

Re: Curing

Although I haven't done homebrew, I'll reiterate my support for heatstop 50. excellent product, no cracks. I slow cured with wet towels and blankets for a week or so, then air cured for 10 days before starting the fires.

I'm running real hot, and no issues whatsoever inside. I was a little surprised, because I expected internal cracks after reading the forum and given that I'm a rank amateur. but nothing.

If it's available in your area, (mine was $50 per bag), I'd use it.

Paul

[brickie in oz]

Re: Curing

Portland based concretes must be cured with continuous moisture to reach useful strength. Typically 7 days minimum.

Your graph just shows it gets stronger over time, which it does.

[david s]

Re: Curing

Yes, but only if you keep it wet. Read the info again.
http://www.concrete.net.au/publicati...f/Curing06.pdf

[brickie in oz]

Re: Curing

After 7 days with no "curing" you cant drive a concrete nail into my mortar, so what am I missing?

[david s]

Re: Curing

It is probably only 40% of its potential strength, But if you think what you"ve got is good enough then you"re good to go.

[brickie in oz]

Re: Curing

Scaremongering? not by you, but the industry?
My mortar cant or shouldnt be any stronger yet its only 40%?
How Bizarre?

[david s]

Re: Curing

mortar is not meant to be really strong as has been previously discussed. You usually make the brew weaker anyway. Typically 4:1 for mortar rather than 3: 1 concrete.

[Lburou]

Will someone kindly talk about curing time for calcium aluminate in home brew?

There is confusion about the term "curing".....snip....
Castable refractory containing calcium aluminate cement does not need this treatment. It should be covered for 24 Hrs only....snip....

Can someone please compare and contrast curing for 'home brew' mortars with calcium aluminate and Portland cement?

Reason being, I used 'home brew' mortar with calcium aluminate -brand name ciment fondu- in place of Portland cement.

Are you saying there is little to gain after 24 hours curing in a wet/moist environment?

[david s]

Re: Curing

Yes, at least that's what I've read from at least two manufacturers/suppliers. It is a slightly different chemical reaction to that of Portland cement and has a different hydration period. I follow the manufacturers recommendations and cover it for 24 hrs. I find cling wrap really good for this. It generates a fair bit of heat while it goes off.

[Lburou]

Intranet search results for ciment fondu and calcium aluminate cement

The ciment fondu website says this on their front page -David, it seems to support your assertion for very short cure times:

Main Properties of Ciment Fondu

• rapid hardening allow return to service within 6 hours
• fast drying times - residual moisture below 3% within 48 hours
• resistant to extreme temperatures and high thermal shock
• provides better resistance to abrasion than Portland cement
• resistant to corrosion from diluted acids, seawater, sugar solutions, greases and fats.

Now David, this is where you say, "I told you so"....

This cement is not adapted to alkaline environment, do not mix alkaline material such as lime.

By the end of my dome, we had stopped adding lime to the calcium aluminate home brew because it set too fast and had surface cracks visible within an hour or two. I would join those who have already recommended James remove the Lime from the FB.com home brew recipe containing calcium aluminate.

[HeidiL2011]

Re: Curing

Hello PlanoPhil,

With the FB modular ovens, you can fully assemble the ovens with the mortar, insulation and the enclosure before curing the oven. Be sure to follow the curing instruction included in the installation guide.

If it looks like there will be rain and the oven is not fully covered with your permanent waterproof enclosure, you should cover it with a tarp. Otherwise the oven and the insulation will absorb water -- which is not good.

If you follow the curing instructions, you will be in good shape. The instructions are thorough. As you go through the curing process, you will see that the oven gets hot much more quickly and there is less smoke with you start the fire.

The reason there is some confusion is because some Pompeii oven builders have wider mortar joints, and use home made mortar where there is more water and it takes longer to cure. Also, some Pompeii oven builders like to start curing the oven without the insulation on to see if any cracks develop both inside and outside the oven dome. But these are not issues for FB oven owners.

Thanks,
Heidi

[david s]

Re: Curing

If you have a layer of vermicrete, which holds lots of water it is very important to dry this layer with sunwind and curing fires before applying the outer shell, otherwise you'll get plenty of cracks in the outershell from the expanding steam.

[PlanoPhil]

Re: Curing

Update - I have finally begun the curing process and like many I have several hairline cracks. Two are vertical in the mortar that covers the seams in the doom (Casa90) and one runs horizontal from the doom into the vent area.

Should I apply Heatstop 50 over the cracks before continuing with the curing process?

BTW - I have not installed the blanket yet.

Phil

[HeidiL2011]

Re: Curing

Hi Phil,

The hairline crack in the outside of the mortar is OK and you can go ahead and insulate and finish assembling your oven.

Phil I will also send you a graphic, it wont let me upload it here.

Heidi