Hempcrete Experimenting

I recently bought some hemp bedding for use in my dog kennels and the chicken coops. I lost my supply of bedding and needed a new source... At least that is the excuse I gave the wife. 

The real reason for getting the hemp was to play with Hempcrete.

I am interested in trying to do a bit of building with this very interesting product. Basically made of Hemp hurds and Lime mixed together with a bit of water. Add the amazing natural processes that happen when you mix lime/water/air you end up with a "limestone" wall that breaths, insulates, and acts as thermal mass all at the same time. Give it a good Skeleton (framing), and a roof with large overhangs, and you have a very nice house.

Then to top it all off this material actually ends up being Carbon Negative. That's right. Negative.

Hemp is very good at sucking in the carbon, and grows really well all over the world in many different climates. But then you add to that the Lime and you get even more carbon sequestration. Sequestration. The lime mixed in actually pulls carbon out of the air and locks it away. That is how this stuff hardens and, over time, becomes limestone. Lime starts out as LimeStone. Through a process that I am not going to go into it is stripped of carbon and changed into a couple different forms of lime. When it is exposed to water and CO2 (carbon dioxide) it reverts back into limestone. Hard as a rock! 

Anyway, I am beginning to play with it.


Here we have our first batch of Hempcrete. Two small batches. Each one is a different mix of Hemp hurds, water, and hydrated lime. I also am trying a few other additives to play with the working time.

   
4:1 + additive                                                             3:1

I mixed these up and tamped them into little boxes yesterday. Today the 3:1 is beginning to harden nicely. I definitely could remove the box and not worry about it falling apart. The 4:1 is not as hard but looks much nicer. The 3:1 has more lime apparent in it. Not as nice visually. Over the next couple months I'll try as many mixes as I can think of. I'll also track down some Hydraulic lime and see how that goes.

Has anyone else here played with this stuff? Or anything similar? I would be interested in peoples thoughts.

Update time:


Here are the two current blocks removed from the forms.
Easily removed. Firm to touch. Slightly damp. Compresses a small amount with moderate pressure from fingers. Heavy with remaining water content. I will weigh them in a few days.


Corners and details from the forms are easily noted. Holds shape with no deforming or slumping.


Although very textured, there is still a very flat surface. Should be very easy to plaster directly onto this and achieve a very good connection.

The 3:1 ratio mix leaves a lime residue on your fingers when handling the block. Should be a couple of weeks before they truly begin to harden properly. We will see.

Keep going, I am very interested in what you are doing. 

Way cool!

Hemp bedding is made of the biproducts from hemp fiber farming, for hempcrete don't you want the hemp fibers themselves?

Emerson,

Actually it is the Hurds that you want. The fibre is a good thing as an additive to concrete or adobe, etc. It is strong and lasts fairly well. But in this application the goal is a material that gives insulation as well as mass. For that you need the hurds.

Hurd is the interior of the stalk. It is a foam like material. Absorbent, so it will soak up moisture and then slowly release it over time. As a dry material has insulation value like a synthetic foam (not equivalent, and not rated with R value). The other part is that it is very coarse and will cause air to be trapped in the material. This again helps to increase the insulation value and the permeability of the wall.

The fibre helps with strength in very stiff materials like concrete. In this case we don't need this ability. Our walls are not meant to hold up the roof, they just fill in the space. They do more then that of course. They do help with the structure, but that is not their main purpose. The hurds and the lime already give the material a decent amount of "flex", so it is not a stiff material that needs help from fibre.

This material should be strong enough to be self supporting and protect the home from the outside weather. Heavy enough to give some mass. It should provide insulation from the extremes of temperature. It should also breath. This is a very important part. We are all used to the idea of building a house to be very tight, with minimal transfer of air through the structure. The contradiction to that is that we do need moisture to move out of the house without coming in. This is not all that easy. A hemp wall is designed to allow moisture to move from one side through to the other side.

At a basic level this movement of moisture can be in and out of the house. But if you provide large overhangs on your roof, and finish the outside with something that will quickly shed extra moisture, you are then minimizing the moisture. The outside can be any thing from lime plasters and stuccoes to wood, metal or vinyl sidings. What ever you wish, as long as it can Breath. Lime plasters and stuccoes Breath. Solid siding must be installed with a 1/2" - 1" air space between it and the wall, and space at the bottom and top to allow this air to flow up and down the wall.

Inside finishes must again Breath. For this you must look at lime plasters or paints that breath. This is harder to find. Most people seem to use plasters and sometimes tint them for colour. The only paint that comes to mind is Milk Paints. Expensive but very nice earthy/natural colours.

Thank you for the encouragement. I appreciate it. Please let me know what you think. I am here for criticism as well.

I didn't know that, thank you for clarifying.

I'm learning all this stuff as I go, so we're all in the same boat.
I enjoy learning new stuff though. That is a major purpose of my life. Gotta learn new things on a regular basis or life gets kinda stale.

Update:

Each block is 7.5"x6.75"x8.5" in size.

I weighed the blocks this evening. 4 days after mixing and forming.

4:1 plus mix is 7.9 lbs, brown in colour, clean look.
3:1 mix is 9.4 lbs, pale brown in colour, light lime residue.

The 3:1 mix also feels to be a little harder when pressed with a finger.

I'll try to weigh these every few days over the next couple of weeks and see how they dry and change.


I will try another couple mixes this weekend, if I can find more time. I need to find a mix that is easy to do, gives a good amount of hardening within 24 hrs, and cures to a fairly hard finish. Once my different mixes have cured and hardened for a couple of weeks I will be placing them outside in the weather. It will be interesting to see how they stand up to the rain, wind, and sun.

In order to get approval for use in construction, I will need to show that it is a viable material.

I am now wondering about hemp in cob. 

Klorinth, thank you for documenting your experiment- you are truly benefitting us all!

Thank you for the encouragement, I really appreciate it.
I enjoy these kinds of things, but I live in a very conservative area. I quite honestly do not have anyone here that has any interest in anything"alternative". They all shake their heads at my chickens and sheep, let alone try to talk about the different design features in my house, or the reasons for the landscaping and pond design, etc. It all makes them glaze over.


Mekka,
I would say hemp could be a very good addition to cob. The fibre that is extracted is long and very strong, and has a good life span. If you used a mixed fibre/hurd cob, you might have something very workable.

Go for it!

Although hurd is used in hemp building promoted by hempcrete, this is because they need to sell lots of hurd!

The hurd is supposed to be a by-product of the hemp fibre processing industry but is now a major market for hemp processors.

The ideal is to use the whole hemp fibre/stalk. Then you can literally 'grow your own home'.

This method is promoted at http://www.thehempbuilder.com - I have tried this technique and it works perfectly!

Very good testing.  Thank you.

I believe this technique is called 'isochanvre' in France and goes way back, actually.

Also, I heard of a woman who built a house out of hempstalks she grew on site.  She planted them in a circle and waited.  She also planted extras.  Then she bent them into a dome, tied them together, wove other hurds horizontally, and then plastered the whole thing with lime-crete.  Beautiful!  Sorry I couldn't find the link for that one.  She was in the USA.

Cheers,

Her name sounds like Madam Perrier or similar. I apologise to her and anyone else for the spelling as I could not immediately find that reference.

The technique is older still however, in Japan there is a hemp house 300 years old. There is a picture here: http://thehempbuilder.com/pictures

earthenhand wrote:
Very good testing.  Thank you.

I believe this technique is called 'isochanvre' in France and goes way back, actually.

Also, I heard of a woman who built a house out of hempstalks she grew on site.  She planted them in a circle and waited.  She also planted extras.  Then she bent them into a dome, tied them together, wove other hurds horizontally, and then plastered the whole thing with lime-crete.  Beautiful!  Sorry I couldn't find the link for that one.  She was in the USA.

Cheers,

Wow.  I love that photo.  I wish I could get one of those.  The house, yes, and a copy of that photo for my slideshows. 

It's exquisite..

klorinth wrote:
...But in this application the goal is a material that gives insulation as well as mass. For that you need the hurds.
...

Well, if that is what you want, how would the inside of sunflower stalks work for the same application? (Some say you are not allowed to grow hemp.)

Dr_Temp,

That is a very interesting idea. Seems to me it is a very similar material and structure.
It just might work. For sure it is worth a try.

Collect  a bunch and run them through a wood chipper. You could even try different sizes to see what it is like.



Update:

The blocks are continuing to dry and change. They are now taking on a white colour. Slowly changing. Getting harder as well. They no longer compress with finger pressure.

Sorry for asking a dumb question, but where the heck do you get hemp hurds from?

I was thinking about insulating my outdoor worm hopper with mud plaster.  Sounds like this would work as well and be more durable, as it's made from lime.

That is far from a dumb question. Hemp hurds are currently imported from EUROPE into USA.

I am actually working with the importers for a more sustainable and local solution to this problem (no hemp processing in USA). See www.thehempbuilder.com for more info. on the solution (coming soon to usa...)

wormilicious wrote:
Sorry for asking a dumb question, but where the heck do you get hemp hurds from?

I was thinking about insulating my outdoor worm hopper with mud plaster.  Sounds like this would work as well and be more durable, as it's made from lime.

I would suggest avoiding putting organic fibers into concrete. If you must, please do long term trials before you build anything serious with it... For your own sake.

Yes, do a 30 year trial before you build please . I think it's more a case of doping your organic matter with concrete than doping your concrete with organic matter. I would think that keeping it dry would be of the utmost importance however. I hear papercrete molds something fierce.

fully agree

research and do proper (engineering) tests before you trial anything new

pubwvj wrote:
I would suggest avoiding putting organic fibers into concrete. If you must, please do long term trials before you build anything serious with it... For your own sake.

Wormilicious,

Hemp hurds and fibre can be imported into the USA from Canada. A lot of hemp is actually produced here on the prairies. It would most likely be cheaper then bringing it in from the EU. Tradical Hemcrete can be imported, but I would hate to see the cost of that.

I forget who does import it but there is at least one company that is importing the hurds. I came across it a few weeks ago while surfing the net.


Edit:
Sorry, I found the cost of the Tradical Hemcrete...

http://www.hemp-technologies.com/page15/page16/page16.html

$12.50/cu foot, if you buy a contianer load. 1800 cu feet. Shipping is then added to that.

You may find it hard to buy direct.

However, it is available in the US. Bales for 30/ 50lbs, with the lime that ends up at about 5-6/cu ft.

Contact via www.thehempbuilder.com if you want access to this.

Thanks for the info.  I'll keep it in mind.  This is really interesting.

Here is a Canadian company that does this type of construction:

http://www.hempcrete.ca/Home.html

They may be able to help with many questions.

Hello all,
Do you think hempcrete would work in hyperadobe-style tubes? I was thinking post and beam frame with 'cretebag walls. Is it affordable?

Thanks! 

our method of hemp building (not hempcrete - see www.thehempbuilder.com) can work in between post and beam frames. But you don't want to use cretebag walls at all - in any form. One of the biggest benefits of hemp building is that it is breathable - ie. a bag would not be breathable and defeat this purpose.

steveowen wrote:
Hello all,
Do you think hempcrete would work in hyperadobe-style tubes? I was thinking post and beam frame with 'cretebag walls. Is it affordable?

Thanks! 

I have to agree with Hemp.
I don't see that there would be any benefit to using the bags.

To build this way you are using a small amount of form work, which is easy to build/use, and is not expensive. You are then mixing and preparing the hempcrete the same way. Dumping it into the forms and tamping it should be easier then loading it into bags then lifting them into position and tamping.

Ease of construction is a major benefit with this. The breath-ability then becomes the final benefit. Remember that this is a benefit that almost all of us are not experienced with, so it is hard to realize how beneficial this could be.

Yes, I see your points, thanks. Breathability is very important. I should have clarified, I was thinking of the mesh-style tubes, rather than the non-ventilated. I've actually had some questions about that approach (hopefully I'm using the right term, 'hyperadobe'"), the mesh-bags or tubes I mean, and klorinth's experiments with hempcrete triggered the idea. Any inputs are gratefully received.

Gotta go to work now, thanks for your replies.