Refractory mortars

[Gulf]

Here is a quick search of the forum and a few discussions about airset refractory mortars.

[MikeD55]

David. I thought airset mortars cure st room temp?

[MikeD55]

So I just read that link. I was under the impression dry airset mortars are hydraulic and can be used for outdoor applications. Unless airset js a general term for dry or wet premix. To be clear I’m only interested in dry hydraulic refractory mortars.

[Giovanni Rossi]

David. Yes agreed regarding the lime. It’s interesting to note the firebrick company uses some type of Fondu cement for their mortar but only discloses it as a two part. Type A and type B. For their render they call it an air set mortar and recommend one teaspoon (5.7g) per 25kg of cement. That’s a VERY small amount. 0.00028%. Would love to know what exactly they use.

MIke, to be clear on the products this company uses: As my earlier post notes, the proprietary refractory mortar + Ciment Fondu is the mortar used for the dome and entry way bricks. The render layers use general purpose cement, hydrated lime and washed sand. The airset product is used to bed the floor tiles and this is the product to which a small amount of lime can be added as an accelerant, if desired.

[david s]

I think you need to be careful which product you select.
Here's the Hefner site that you quoted. Some of their products clearly say "curing between 600-800C"

https://hart-keramik.de/en/wp-conten...rogramm-en.pdf

My own experience with refractory mortars iand oven building is limited to CAC based mortar, homebrew and Vesuvius wet mortar in a bucket which is a sodium silicate based product. Of the three types in regard to performance, joint thickness, workability and price for a wood fired oven's service temperatures, I find the homevrew the best.

[MikeD55]

David I think that’s the wrong company. Here’s the link

https://www.hafnertec.com/baustoffe/moertelprodukte/

[david s]

Sorry, I can’t read that, it’s in German.

[MikeD55]

This is the translation:

1. Hafner HaftHeat 1000

-Fiber reinforced

-Crack free

-Shrink free

-Very forgiving

-1-60mm joints

the mason who turned me on to this builds masonry heaters and brick ovens with it. He said he’s never seen anything like it in this country.

[david s]

Sounds interesting.

[MikeD55]

I wish there was more info available on it. I believe it’s made in Austria.

[david s]

Unfortunately you just have to go with what’s available to you. There are a few products I would love to use but can’t obtain or would be too prohibitive to freight, like silicone coated perlite, foam glass, hydraulic lime and waterproof cal sil board. There are already some products I get that cost more in freight than the cost of the product.

[MikeD55]

I’m I can get it (HaftHeat). The Mason who uses it is a couple of hours away from me and imports it. Just wish there was more info on it.

[david s]

Google translate gives me this


Haftheat 1000° – The perfect adhesive mortar for fireclay and tiles The building material HAFTHEAT 1000° consists of high-quality ceramic materials and has the best adhesive properties as well as very special fiber reinforcement, which makes it easy to process. The adhesive mortar is temperature-resistant up to 1000° C and can therefore be used universally in oven construction. Haftheat 1000° has NO chemical additives that could give off harmful fumes when the oven is started up. heat resistant up to 1000° fiber reinforced crack-free application thickness 1-60 mm shrink-free individually adjustable processing time (delay liquid) 15% more efficient than comparable products

It sounds to me like it is a CAC based mortar with fibres (probably polypropylene) added which provide some strength to help hold the mortar together, but burn out at low temperature (160C). This feature allows thicker joints to reduce the possibility of steam spalling. I advocate adding these to homebrew to achieve the same outcome.
The little bottle of stuff sounds like a retarder (probably citric acid) to extend working time. Chilled water is an alternative method of extending the working time of CAC based mortars and castables.

[MikeD55]

Good to know. I’m gonna inquire into the fibers. I’ve emailed the manufacturer

[david s]

It would be preferable to enquire. Leave the inquiry for a later date if the product fails.

This might sound like a trivial error, but can be easily misinterpreted when translations are made. You wouldn’t want them to think you were considering legal action before you’ve even bought the product.