Anyone added biochar into cob/adobe to make walls or roofing?

I came across some very promising studies on the use of biochar as an additive to cement. Has anyone tried mixing biochar into their cob or cement mixes and would share their results?

Links: https://www.biochar-journal.org/en/ct/3 (scroll thru the middle paragraph if you don't speak Deutsch, or whatever that is)

http://e-biocharbricks.blogspot.com/

www.ithaka-journal.net/55-anwendungen-von-pflanzenkohle?lang=en (scroll down)

Conner Goertzen : A Fellow member Dale Hodgins has proposed the use of bio-char both as insulation and as a surface treatment to increase Solar Gain.

See link below !


https://permies.com/t/19303/natural-building/Dale-Marvellous-Inventions-Adaptations

Awesome! I knew someone else on this forum had to have come up with the same conclusion-- just didn't see the topic clearly defined as I was searching. Thanks, Allen!

Conner Goertzen wrote:I came across some very promising studies on the use of biochar as an additive to cement. Has anyone tried mixing biochar into their cob or cement mixes and would share their results?

Not sure if this thread is still active, but we're in the process of designing our new office on the farm using adobe construction, and we intend to use rice husk char in the mud bricks (if they are able to retain their load-bearing strength) and interior/exterior plastering.

I have not considered this use for biochar.

Opening more doors for me learn, thank you.

I've kicked around the idea of adding granulated charcoal to a section of rammed earth wall as the collection surface of a solar chimney; glad to see people more experienced and knowledgeable than me have had similar ideas!

I made a light weight cement ball using a 3:1 Ratio of Biochar to cement.

I saw a web link where they are experimenting and it floats. ( I think I need to build a bigger block.)

I also did a 1:1 Ratio of earth to clay mixture for a black Dorodango - it turned out nice.

Kevin Tracy wrote:I made a light weight cement ball using a 3:1 Ratio of Biochar to cement.

I saw a web link where they are experimenting and it floats. ( I think I need to build a bigger block.)

I also did a 1:1 Ratio of earth to clay mixture for a black Dorodango - it turned out nice.

I would like to hear more about your charcoal cement.  Any info you have, like how strong it is, how weather resistant, is it waterproof, how insulating is it, etc.  This would be something really fun to try and inexpensive if I could use it to making building blocks.

I posted about this awhile ago. In the book and interview, Albert Bates talks about how biochar can make cement stronger,and it is a way to sequester much more carbon.

https://permies.com/t/131013/Mercola-biochar-article-interview-Albert

John S
PDX OR

Bio-char one is very insulative, therefore you would save in that way. It is very frequency absorbent, therefore lower pressure, and should make you feel lower pressure. It's low pressure means you will have more water in your soil, even used un-attached to soil.

we are doing it.. its awesome! like with cement you need to hydrate the char before use. It can hold six times its own weight in water, so you must factor this into your mix. You can work with this "internal curing potential" in both cement and cob. Meaning it will dry faster, and from inside as the char soaks up moisture, so be prepared.

I only partially hydrate my char before dry mixing in the sand and the straw in a wheelbarrow. Then I add the clay and mix by hand... adding water as needed. Leaving this overnight can yield a nice dry moldable char-cob. I arrived at this thru trial and error, you will have to adopt to your particular ingredients.

Ive been using Manzanita char that I sent thru a wood chipper, that left me with 1/4 inch chunks down to powder.

6 shovel-fulls char  /  2 shovels sand  / 2 hand-fulls rice straw  /  2 pails (~2 gallons) blended clay soil (wet)  /  1 gallon water.

I love to potential to replacing much of the sand in earth building, with biochar. It could mean lighter better insulated buildings made from a carbon negative material that can be made locally from a wide variety of sources.

I have worked with 100,000's of earthen bricks, that does not make me an expert but I know how to spend my time wisely.
Some thoughts on bio-char in the mix;
- never heard of it prior to reading it here
- saving weight with an earth brick may not be important
- as insulation it may be minimal because insulative material needs to be consistent.
- I suggest the additional work involved with the bio- char may not a a real benefit.
- I will have to study the claim that bio-char improves the action of cement.
- use of cement is not nescessary if you have the correct soil in the first place.
- when clay dries faster it sometimes cracks.

Rammed earth as we do it today doesn't pass muster with modern energy codes.  Builders are faced with adding a layer of insulation to get permitted.  I don't want to give up on the idea of rammed earth.  Can I add enough biochar to increase insulation enough to get the job done?  I found the following in one paper online so I guess don't go over 10%.

Biochar was used as a replacement for cement and aggregate in cementitious composites and as an addition in wood polypropylene composites and plasters. The biochar dosages ranged from 0.5% to 40%; in most composites, the addition of biochar increased strength and reduced thermal conductivity and the bulk density of fresh mortars. Also, biochar dosages of 0.5–2% decreased, while dosages of 10–40% increased water absorption and penetration on cementitious composites.

Thanks for any advice.
David
South Carolina

David, where is the source of that statement please?
Is any biochar added as a powder or as lumps?  
FROM; [url=https://www.ithaka-institut.org/en/ct/97#:~:text=Two%20of%20biochar%27s%20key%20properties,insulating%20buildings%20and%20regulating%20humidity.]ITHANKA INSTITUTE[/url]

URL SYSTEM NOT WORKING HERE!!!
"The first building using this material was built in 2013 at the Ithaka Institute in Switzerland and is currently undergoing extensive performance testing.
Already though, the building has proven to be highly insulated with great humidity control.
Substantial opportunities also exist to use the char-clay material to upgrade existing buildings plagued with poor insulation, humidity problems or contaminations such as lead paint.
Two of biochar’s key properties are its low thermal conductivity and its ability to absorb water up to 5 times its weight.
These properties mean that biochar is just the right material for insulating buildings and regulating humidity.
In combination with clay, but also with lime and cement mortar, biochar can be used as an additive for plaster or for bricks and concrete elements at a ratio of up to 80%.
This blending creates inside walls with excellent insulation and breathing properties, able to maintain humidity levels in a room at 45 – 70% in both summer and winter.
Not only does this prevent the air inside the rooms from becoming too dry which is a potential cause of respiratory problems and allergies, but it also prevents
condensation from forming around thermal bridges and on outside walls which could lead to the formation of mold."

Also from the same reference above;
REPLACING SAND WITH BIO CHAR
"...lightweight biochar-concrete panels, biochar-lime bricks, indoor and outside insulating plasters or wallpaper and tile adhesives.
With wet bulk densities under 1.2 g/cm3 and partly under 1 g/cm3 and a compressive strengths around 20 N/mm2, this very exciting, highly functional
lightweight material will soon be making its appearance!
When using cement and lime, sand can be completely replaced by biochar reducing the weight of the material by factor 5."

I think this is the correct link to the aforementioned article:
Ithaka Institute: Biochar as Building Material

I cannot work out why the link I supplied is failing, if anybody can help, Thank you