Mixing refractory cement for casting.
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- เผยแพร่เมื่อ 18 ก.ย. 2024
- I hope this short video will help some people to successfully cast high temperature concrete. I used polyurethane foam to make the mold, I cut out the shape on my bandsaw and covered the foam with PVC damp proofing membrane as I know the cement won’t stick to it!
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Nice demonstration, thanks.
I can't wait to see where this is heading.
Hi there. Thanks for sharing your knowledge, it’s very helpful. I’m about to build my own outside wood fired oven. Most people seem to use vermiculite or perlite to cast the dome and use fire bricks for the oven floor. I was thinking about using perlite for the dome. I have some reclaimed fire bricks which I believe came out of some old storage heaters which I plan on using for the oven floor, although I was wondering if I could use fire cement instead of the fire bricks so that the surface is smooth with no joins for the peal to catch on. I was wondering if you have any thoughts about this and also if you could explain how to make my own refractory cement. Cheers, Steve 👍🇬🇧
@@steveandsherilyn7543 Hi Steve, yes lots of videos about folk making wood ovens from vermiculite and cement mix but, very few videos showing how long they last!
First you need to realise how a traditional wood oven works, we are going back to Roman times like 2,000 years ago, even back then the builder had worked out and understood that heavy clay bricks are the best material to use because they hold heat for a long time and that heat will radiated back into the oven space.
This is what we call a high mass oven.
A high mass oven will take around one and a half hours to fully heat up but will hold heat for two days.
On the other hand vermiculite is a low mass insulating material that wont hold any heat and also crack up after a few hot fires.
So by far the best and most effective ovens will use a dense, high mass material to hold the heat and an insulating layer over the top of that to hold the heat in place.
So a solid brick or refectory cement, dome is covered with a cement and vermiculite mix or other insulating material.
An oven built like that will last a life time and not half a summer!
A brick base is the best because it will hold the heat and absorb moister from the pizza base, there wont be any ridges to catch a peel if built accurately.
However if you dont want to invest in good quality fire bricks (they are expensive) it is possible build a DIY refractory cement dome over a mould of sand.
It would take me a long time to explain how to do this so I advise you join the Forum called Forno Bravo. There you will find every detain needed to build a cost effective high mass oven.
First video talking about the plastic fibres. Made me think what if you used broken up styrofoam instead. They make small little balls.
Well I have heard of people using salt and polystyrene (styrofoam) but nylon fibers are the tried and tested method. You can buy ‘counter top’ reinforcing fibers from many stores, they are extremely thin and wont effect the overall strength of the finished product.
I think the little poly balls would be far too big for our purpose.
@@foxfish7115 well at first i thought using hair due to another video of someone trying to make clay, then thought about the styrofoam. Then i scrolled down after commenting and saw the comments using nylon rope. Lots of rope around my parts since its a fishing town. Great video, i appreciate you taking the time to respond to my comment.
@@rashadabdullah9769 yes you could try nylon rope although try to find really thin stands as possible, human head hair would be closer to counter top fiber thickness. I think a lot depends on the project and its use but we are looking at around 1% added to the mix. Make sure the fibers are evenly distributed in the dry mix before you add any water, it can be very frustrating and time consuming to get them spread out evenly but worth the effort. Good luck and please let me know how it goes …..
@@foxfish7115 i want to build a stove, on the ground. That is my intention. First i gotta build my home, but def will be dirt floor. This way the floor will be a heat sink. I also want to mould a large water tank where i can just throw buckets of snow to melt. Right now i am tied up with a project i started 2 years ago, a new (my third) bike trailer for my moped. Once thats built this spring and all goes well i will be saving and planning my next projects: chicken coop, or rabbit, summer home and winter home. Here in canada i hate how all homes are built with solely winter in mind.
@@rashadabdullah9769 you will need to isolate the fire box from the earth otherwise as you say it will become a heat sink and not allow the fire box to become hot enough to burn the smoke!
Anywhere, where there is a flame, must be very well insulated. After the flame you can steal the heat but leave enough to power the chimney. Keep me informed when you start planing…..
Try first coating your firebrick or perlite with shampoo or dish soap just enough to dampen it it won't penetrate not make sense in Portland cement only enough to coat it lightly allow that to dry by doing this your refractory mix will now need much less water cutting your cure time and helping any issues with cracking
Thank you for your comment although I dont quite understand the benefits of coating anything with soap.
I guess you are suggesting that the soap will somehow seal the grog but I would think it would lessen the adhesion of the fondu cement to the brick. The set time is already very quick at around 15-20 minutes.
The main issue for me is that the grog I buy is a mixture of crushed fire brick and firebrick dust, it would be very difficult or at least very time consuming to sieve out the dust, coat the brick particles, dry the particles and re mix them?
Maybe for small projects it would be worth trying but I use a lot of my refractory mix and to be honest it works extremely well with the correct amount of water and added fibres.
However it is an interesting suggestion ….
@@foxfish7115
Could you tell us how much of the Poly and Carbon fibers you add to your mix? Thank you
@@TheLitVic That is a difficult question as I tend to judge it by eye, I will have to try and work it out and get back to you….
@@foxfish7115 Thanks a bunch for your support!
I have some Nylon rope I've cut into 2" lengths, would you do shorter or longer than that? Now to find some carbon fibers...hmmm
@@TheLitVic I am not sure how to measure the quantities as carbon fiber is so light, it is difficult to weigh a cup full of loose fibre.Not quite as bad but is the same with poly fibers! I would say about a half cup of loose carbon fibers, about 20mm long and quarter cup of 10mm nylon or poly fibers per 20 kg mix. Longer fibers would be better but they become impossible to mix after a certain length. Carbon fibers are incredibly thin, only a fraction of a human hair and they form balls if you are not careful and that would have a negative effect! I use polypropylene fibers for the melt out effect, I buy them as ‘counter top cement fibers’ or concrete reinforcing fibers, from my local hardware store. They come in two lengths, 6mm and 10mm, the short ones are much easier to mix but if you are going to use nylon rope I think you could go for 10mm long. like I said in the intro, it is far easier to buy ready mixed refractory than to make you own but, as I was making 300kg pizza ovens, that was not economical for me! Good luck and let me know how it goes.
nice, can you melt cast iron with it?
@@bigdilliams ha ha I doubt that very much…
Great design and craftsmanship my friend! Thank you for sharing your details.
I'm going to follow your inlet and burn chamber design but also add side risers as this Japanese builder did. Should be able to control air flow to the side air risers with a simple baffle.
th-cam.com/video/NJENCc3o_-Y/w-d-xo.htmlsi=SdIwg9zegI-CwroB
Keep up the impressive work!
Great video, thank you for sharing. Could you please share the ratio of your mix? I am willing to make a pizza oven with castable refractory concrete. And make the mix myself. Your help is greatly appreciated. I am feeling overwhelmed with all the content on the net. Thank you very much !
For a pizza oven there are two main options …. Four parts crushed fire brick and one part high temperature cement (cement fondu) or what is called ‘home brew’ one part portland cement, one part lime, one part fire clay four parts sand.
Nylon fibers should be added at 1% in both mixes.
Good luck.
Thank you very much@@foxfish7115 , any thoughts on the 4:1:1 ratio (4 parts Perlite, 1 part sharp sand, 1 part refractory cement)?
I am planning to cast it in 6 pieces, so to allow for thermal expansion.
@@ariadnasol you do not want to add insulating material to a pizza oven, you want the opposite = dense mass to hold the heat.
You can then cover the mass with insulation to hold the heat inside the dense mass.
If you look right back on my channel there are a couple of pizza oven builds that I did .
@@foxfish7115 Thanks again, makes all the sense in the world. I will look into your other videos. Have a great day, and thanks again for your quick replies. Salud !
@@ariadnasol no problem just ask any questions….
Do you think rockwool fibers could subsistent e for your carbon fibers?
I dont think so as they have no structural strength, the longitudinal strength of carbon fibre is immense and it is readily available and cheap for this purpose. You can buy a small piece of carbon fibre and cut it up with scissors, even a small piece will provide tens of thousands tiny fibres. The Polypropylene or nylon fibres can just be cut from a piece of rope but I buy mine as they are commonly used in cast concrete and are available cheaply from my local store.
@@foxfish7115 Thank you for you great explanation!
Out of curiosity, is ciment fondu the default
cement where you live,?
Amazing to see the liquefaction!
@@foxfish7115 Are rock wool fibers the same as basalt fibers? I think basalt fibers have significant tensile strength. I have some ~50mm long basalt fibers with a cement-compatible surface coating which I hope to use with refractory cement.
@@GreenRainbowParty I think rock wool is made from Basalt, Basalt is a volcanic rock. Try it and see what happens? Perhaps make some small samples and see if they crumble after a few days of drying, then put the samples in a fire for 10 mins…..