Crack Control and fiber addmixtures

[BruceKWHP]

I just found my username and password on a dark web alert using "Pentester.com"

scary.

[david s]

I use both AR glass fibres and basalt fibres. For the price of each and the recommended dosage:strength attained, there is little difference. A slight improvement of strength <400C for basalt, but over 400C the AR glass fibres are stronger. For this reason I use 50/50 of each. Both are ok for the service temp range we use. For mixing I prefer the AR glass fibres because they disperse in the mix better. The basalt fibres tend to clump which requires extended mixing time. Both are soft to handle. My AR glass fibres are all of a uniform length and thickness, while the basalt fibres I sourced have varying length and thickness. This could vary from different suppliers.
As well as stainless needles (melt extract fibres) which are used with dense castable hot face, I use the very fine as well as the thicker and longer pp fibres and nano fibre reinforcing (one graphene based and the other carbon nanotube based), which provide reinforcing on a molecular level. I only use these out of interest and have yet to conduct flexural strength tests on sample cast bars next month when I hope to have more time.

[microbe]

A year on from my build I have decided that worrying about cracks is over-rated.

Mine has a fairly long crack along about 50% of the length from front to back. When I finished the build I was really concerned about the crack and kept patching it. Each time I used the oven, the next day I would fill the crack with mortar and then next time it would open up again.

Nowadays I am not worried about it at all.

It opens up when the oven is hot and closes when it cools down. For sure some rain gets in, then when the oven is fired, some steam comes out for a while No doubt the insulation is compromised, but big deal...we make 15 or so pizzas and are not counting on retaining the heat.

It makes outstanding pizzas.

[microbe]

Gold Coast, Australia - chopped basalt fibre is available by the kg ($22) from carbonparts(dot)com(dot)au

Finally found some locally...

[Gulf]

Sorry, it seems posting a URL isn't permitted, it kind of spoils the power of sharing info, I reckon.

+1 on Russell's post.

Direct links outside of the forum can lead to some nasty phishing, spamming, and viruses. There are work arounds that can be used and are done all the time. The name of the product and who sells it can be written out in the post. Just no direct commercial links. Direct links are what gets the spammers there quota for their big$. Anyone can do a search for the "product name" and "who sells" it based on the key words provided. Also, a print screen can be done of product data sheets if someone is asking for advice.

It's a shame that we have to do this but that's the way the world is now a days!

[UtahBeehiver]

Yes it is unfortunate that we have to restrict links to third party sites but the Forum has been hacked several times where members have lost several weeks worth of post and info.

[david s]

Chopped basalt is available from Southern Basalt Supply in Tasmania. $12.40/kg plus postage which was more than the cost of 2kg of fibres.

RF Composites in Geebung (Brisbane) have 3mm AR (alkaline resistant - for concrete) chopped fibre for $8.75kg + GST, but it is only sold as an 18 kg bag which is way too much.

Sorry, it seems posting a URL isn't permitted, it kind of spoils the power of sharing info, I reckon.

If anyone can find someone who will sell small bags of AR fibre, post the info here.

I get my AR fibreglass fibres from a different supplier in Sydney, min supply of 20 kg. Yes they are expensive, but yours is a better price than I pay and I also have to add $100 for freight. Because they reduce so much labour I'm still well in front as opposed to using chicken wire. In addition to the AR fibres I also add the really fine propylene fibres whic reduce slump cracking, but not flexural strength. The AR fibres are widely used by the concrete countertop manufacturers, although that game is not as popular in Australia as in the US. If you can source one they may be able to sell you a smaller quantity.

[microbe]

Chopped basalt is available from Southern Basalt Supply in Tasmania. $12.40/kg plus postage which was more than the cost of 2kg of fibres.

RF Composites in Geebung (Brisbane) have 3mm AR (alkaline resistant - for concrete) chopped fibre for $8.75kg + GST, but it is only sold as an 18 kg bag which is way too much.

Sorry, it seems posting a URL isn't permitted, it kind of spoils the power of sharing info, I reckon.

If anyone can find someone who will sell small bags of AR fibre, post the info here.

[microbe]

So, during firing #2 a crack opened up in my 10:1 perlcrete insulating layer (75mm) over the house-brick dome, yet to be rendered. It closed up again when the oven cooled so I am not particularly worried about it,

I had an idea and would appreciate feedback.

I plan to fire 3 more times before rendering (looking forward to guests tonight) to give everything a chance to really dry out.

Would it work to cover the dome in glass fibre insulation, then chicken wire and render onto that.

My thinking is that the glass fibre will create a bit of expansion space, saving the final rendering shell from cracking.

Thoughts?

Thanks in advance

[UtahBeehiver]

Plus one with David's response. There are a lot of YouTube vids out there touting perlcrete dome ovens. They are not in your best interest for a long lasting and effective oven.

[david s]

Do some more research. A perlcrete dome lacks the required strength, thermal mass and conductivity. However, it is a good insulator if used over brick or dense castable

[TM66]

Hi all,

I'm about to start on a Perlcrete dome home project myself and was browsing the internet for options for dome reinforcing.
To be honest, I don't much like the look of positioning and setting the chicken wire method in a just laid dome, seems a bit haphazard.

Fibres added to the dome looks like agreat option, and when I saw the Tasmanian reference I was very interested.

Cheers.

[UtahBeehiver]

You can post info on basalt fibers such as a screen shot or txt file, we want to avoid direct commercial links due to spam, phishing or site promotion issues.

[david s]

Since the product has been removed I can’t tell what you’ve used. I’ve been using AR glass fibre reinforcing in the cladding layer on my ovens for years. Having deconstructed one and found that layer in very good condition I’m sticking with it.
I also now use carbon nano tube reinforcing (reinforcing on a nano scale) with both standard concretes, homebrew and castable refractory with good results.

[microbe]

This is an old thread but the info is still relevant.

I have just found this: which seems like it might be a new reinforcing additive. The good news is that is on the Gold Coast...where it is so hard to find WFO materials. But they only sell 5kg bags for $99.

This mob sells by the kg -from Tasmania

The other good news is that I am really happy with this...

First pizza, Christmas Day 2021

Thanks to all the people who have posted stuff in this forum (especially you, david s ), couldn't have done it without the info.