Vermiculite and cement to make refractory?

[sparke]

Can anyone tell me what is the best way/ratio to mix vermiculite and cement to make high temp refractory? Can you use regular Portland cement or do you need to buy refractory cement? Refractory cement is expensive and the project I am thinking of will need several hundred pounds worth of cement... I have not had much luck trying to research this on the internet.

Thanks!

 

[emesine]

I'd like to hear from an expert, but I would guess that standard portland cement will break down quite easily at high temperatures. I would certainly use refractory cement. I have worked on the construction of a kiln or two (for ceramics, 2300F), it can be tricky. What are you trying to build?

 

[patch53]

Personally, I wouldn't monkey around trying to make your own refractory material. Just buy the refractory cement. You just mix it with water to the proper consistency, pour it into your forms and wait till its done hardening. Keep it damp and slightly cool as it hardens by keeping it out of the sun and put some damp towels over it.

When I built my Seton I got all my refractory cement from John at Bethel Eng. in Ohio where the Setons are now made. He gave me a much better price than I could find anywhere on the web for refractory cement.

Pat

 

[sparke]

I am changing the design of my Greenfire boiler(Seton knock off). What I have in mind is going to take 500# or more of refractory. It will not be subject to the extreme heat in the main fire box. I was quoted $63 for 50# from a local vendor. The ss needles are going to be another $15 a pound. At those prices I am not going to follow through with the project. Thanks for the lead at Bethel. I will give them a try. If I do the project I will document and post it as usual...

Patch - if you have an email address for John , can you PM me? Thanks

 

[mole]

I am changing the design of my Greenfire boiler(Seton knock off). What I have in mind is going to take 500# or more of refractory. It will not be subject to the extreme heat in the main fire box. I was quoted $63 for 50# from a local vendor. The ss needles are going to be another $15 a pound. At those prices I am not going to follow through with the project. Thanks for the lead at Bethel. I will give them a try. If I do the project I will document and post it as usual...

Patch - if you have an email address for John , can you PM me? Thanks

Sparke,
No fair teasing like that! Can you share more?

 

[Adios Pantalones]

Do you want dense refractory, or insulating refractory?

Vermiculite adds bulk and some insulating factor. The portland cement shouldn't be a large percentage.

Most recipes that I see call for fireclay, sand or grog, 1/10 to 1/8 cement, and sawdust or vermiculite if insulating. Some also add more alumina for high temp operation (talking kiln building for almost 2400 F).

 

[ironpony]

refractory cement can be made by mixing
1.5 parts portland cement
2 parts fireclay
1.5 parts perlite
2 parts silica sand

you do not want to use vermiculite because it absorbs water which will turn to staem and crack the cement when heated
this recipe is used for kilns so temperature is not a problem, but you must cure it sloowly and then start with small fires to
further cure the refractory
do a search there is alot of info out there
backyardmetalcasting.com is one

 

[sparke]

Mole - So hard to put my thoughts into words. Basically I have an idea to address the issue of cleaning the heat exchanger much quicker, cleaner, easier.

Adios - I am looking for insulating refractory.

Ironpony - thank you for that info. That is exactly what I was looking for on the web and was unable to find.

 

[Adios Pantalones]

Ironpony- that's for dense refractory. perlite or sawdust is added for insulating- sawdust burns out. You need some slow dryout fires to prevent issues.