Papercrete bench

We are trying to figure out if we can make the bench out of papercrete ?
The pipes in the bench would be covered with vermiculite and over that
would be poured in PC. The stove itself would be cement and metal pipe.

Has anyone out there done this of have any information on doing it this way.
Thank you

A couple of issues come to mind. How combustible is papercrete? (I know you are isolating it from extremes, but still...) How insulating is papercrete, and how dense is it? You want something that will absorb a lot of heat energy, and transmit it slowly out.

The vermiculite is definitely a bad idea. You would be effectively insulating the ducts from your thermal mass, which would prevent it from extracting the heat.

You also mention "cement and metal pipe". Ordinary cement (portland) will break down at the temperatures experienced near the combustion zone, and metal (any kind or thickness) exposed to the flames will quickly melt or corrode. You need to use refractory cement or masonry, with no metal in the high-heat zones. The barrel will be safe because it gets less than the highest temperatures and the gases are fully combusted and inert.

Thank you so much. We were just wondering if it would work. Thank you for taking the time to
explain that and making it where I can understand it.

Anne Flatmo : Please don't !

Starting from the last and going forward ! As you are expecting to have a bench then you will be attempting to build a Rocket Mass Heater, Rocket (cook) Stoves
are something else altogether !

The incredible efficiencies of the Rocket Mass Heater RMH, and its squeaky clean burn are directly related to the Freaky High Temperatures that a RMH consumes
the wood it is fed 2,000ºF +, at these Temperatures any iron or steel metal used in the combustion core is Going to fail!

If you are interested in the Technical reasons you can Google "High Temperature Hydrogen Attack "!

At these temperatures any Portland Grade Cement will also fail! This means that no Cement should be allowed in the RMHs Rocket Burner portion, it should be
replaced with a specific mixture of Sand and Clay (Cob)

The reason for running your pipes through the thermal mass is to have them 'give up' their Thermal Energy into the Mass of the Bench, Therefor covering them in
an insulating material like vermiculite or perlite is exactly the opposite of what the stove pipe and the thermal mass are both designed to do !

Basically, Unless you have already had a lot of experience with papercrete I have grave doubts of your satisfaction with your finished project, Again you are
substituting a material with Known insulating properties for the Monolithic mass that You need to use to receive the high Heat Energy output of your Rocket.

Your final choice for finish material will only trap a small amount of heat energy and the bulk of the rest of the heat will be channelled through your bench and out
of your house and into the environment !

This is where I Strongly suggest that you consider going to Rocketstoves.com to download a PDF Copy of the Brand New 3rd Edition of Rocket Mass Heaters

With 100,000 + RMHs made world wide, this is 'The Book', most every RMH was made from this book and 95% of all of the 1st time builds (that worked ) were
made following 'The Book'.

THis book with save you money by keeping you from buying materials that WILL fail, and also save you time and frustration for this and many other important
reasons !

You have joined a group of fellow rocketeers who want to see you succeed, please listen to My heart felt plea. We still have time to do it right !

For the good of the Craft Big AL

Remember what I said about Cob a mixture of Sand and clay? We are talking about the dirt under your feet ! It won't burn, rot, insects won't eat it and its as cheap as Dirt !

Thank you ...Just purchased the book. That will help us make the right choices.