Jump to content
Sign in to follow this  
JamesMusslewhite

Hempcrete and Coco-crete - Possible Atlternative to Hollow Block/ Concrete Construction

Recommended Posts

JamesMusslewhite

I have been looking at materials for building a home that would be lighter weight, stronger, and affordable as an alternative to hollow-block construction. Hollow block requires steel and tends to fail in earthquakes. Hollow blocks are made so poorly and concrete begins to lose integrity in 35-45 years so the structure deteriorates. There is also the expense of the heavy steel rebar needed to strengthen the columns, beams, posts, and walls. The shear weight requires the pouring thick concrete foundations and floors which makes homes extremely heavy which can be problematic on hills and sloped properties.  

 

One thing that caught my eye was a product called hempcrete which seems to be a fascinating product with incredible properties.

 

Hempcrete can be used with basic wood frame construction which is considerably cheaper to hollow block / steel rebar construction.

 

Edited by JamesMusslewhite
  • Like 1

Share this post


Link to post
Share on other sites
JamesMusslewhite

It is the use of wooden frame constriction to act as load-bearing walls and beams that is so interesting. Even the use of coconut wood in non-weight-bearing walls and basic white pine in load-bearing walls allows for easy construction and reduction of cost.


 

 

The fire retardant properties of hempcrete is another good selling point

 

The primary downside is the availability of the hemp fiber and the volume of hydrated lime could easily be problematic here in the Philippines.

  • Like 1

Share this post


Link to post
Share on other sites
JamesMusslewhite

So I started looking for a possible alternative as a replacement to the hemp fiber and during the research I found a more readely available and much cheaper solution using shredded coconut fiber, less lime and concrete.  I ran across this article http://arkitrek.com/http:/arkitrek.com/cococrete-mixing-instructions/

 

 

Cococrete Mixing Instructions by Ian | February 25th, 2013 | Green Materials & Products, Tinangol Kindergarten | No Comments


NSlider-cococrete-542x200.jpg

 

Coco-crete is a low-carbon lime-based composite concrete. Arkitrek have been experimenting with a mix of; coconut coir, river sand, dry hydrated lime, portland cement & water. Lime and cement are destructive to nature because their production necessitates quarrying of limestone. We think that lime-based bio-cretes, such as coco-crete may go some way to mitigating environmental damage.


The following are instructions for mixing a 10:5:4:1 (coir:sand:lime:cement) by volume for a cast in-situ wall.


We have previously experimented with a mix ratio of 10:5:3:2 (coir:sand:lime:cement) by volume. This mix creates a dense concrete-like material with a characteristic compressive strength of around 5N/mm² after 4 months (methodology). This is stronger than we need for self-supporting non-loadbearing walls and we are now optimising the material with less cement.


Health and Safety

Cement and Lime are corrosive alkaline so we recommend wearing boots, long trousers, waterproof gloves and safety goggles for protection. The photo below is of the ‘how not to’ variety. If you get the mix on your skin rinse it off in clean water. If it goes in your eyes, rinse it out thoroughly. Shower after coco-creting and apply moisturising cream where lime/cement has been in contact with your skin. Other on-site risks, such as cutting off toes with a spade, are also present so do your own assessment and take appropriate precautions.

 

                      

cococrete-03.jpg

 

Step by Step

 

Step 1: Make your formwork, making sure that it is robust and water tight.


Step 2: Pick your vessel of measurement – small wheelbarrows work
well, where we counted 50kg cement or 25kg lime as one wheelbarrow.


Step 3: On a clean surface, thoroughly mix the dry cement, lime and sand until it is a uniform colour


Step 4: Soak the coconut coir in water. Do this by filling your measuring vessel with 1/3 water and pack in the coconut coir, compressing it down into the water with your hands. Soaked coir will hold itself down after compression. This amount of water also seems to be about right for a workable mix and extra water may not need to be added.


Step 5: Progressively add the soaked coir to the dry mix. Tearing it into smaller clumps helps workability. It’s easier to mix if you spread your pile out rather than heaping it up. Mix until it is all an even colour. There should be no clay-like clumps of sand/lime and similarly no stubborn bunches of coir which are still brown in the middle. The mix should look like grey fibrous slimy coir and have minimal liquid leaking out. It it’s too wet, add some more coir.


Step 6: Pour into the formwork. Well ‘pour’ is the wrong verb. Slop it in in thin layers (less than 100mm). Rake out any stubborn clumps and tamp thoroughly with a stick. A 50x25mm (2″x1″) stick works well at a length to suit the depth of formwork. For a rake, try putting a 4″ nail or two part-way into the end of your stick. This makes breaking up stubborn clumps much easier. The objective is to avoid voids. Don’t pour more than 450mm (18″) at a time unless your formwork is very strong.


Step 7: Allow 5 days before striking the formwork.

 

cococrete-02.jpg

                                                      

A Note on this Coco-crete mix

We have used the above mix for self supporting non loadbearing walls up to 1800mm high and 200mm thick. We have not tested the compressive strength of the above mix yet, although as noted an earlier mix with more cement achieved a characteristic strength of 5N/mm² after 4 months (methodology). Typically, infill walls in Malaysia use sand:cement or clay bricks with a compressive strength of ±2.0 N/mm² so we are over-engineering at present.


We’d like to omit cement all-together, in favour of lime, but in the very high humidity of the Malaysian climate we’re being cautious about how quickly a lime-based biocrete can loose its moisture and achieve minimum strength needed to be self supporting. We think that cement speeds up the curing process, leading to a stronger wall more quickly. For the same reason, coco-crete may not be suitable for bricks given the long time required to cure in the mould.


A similar European product, Hemp-crete, uses a 1:4 mix of lime:hemp shiv as an infill material for framed walls where timber or steel frame does the load-bearing and the biocrete is used for its environmental performance. We will be experimenting with a similar coco-crete mix soon.


A Note on Coconut Coir

Our coconut coir is sourced from a mill near Kudat in Sabah which produces coconut husk mulch for an acacia plantation nursery. The coconut husks themselves are by-products from the copra or coconut oil industry. The coconut husk is the fibrous mass that surrounds the coconut kernel. It is green or yellow when young and seasons to brown. Seasoned coconut husks are fed to the mill where they are ground up, spitting out crumbly mulch at one side and tough long fibres at the other. The mill that we go to has no other use for the fibres and if we don’t use them, they are burned.


A Note on Sustainability


A drawback of our method so far is that cast in-situ walls use a lot of timber for formwork that may go to waste afterwards. On the other hand, thick monolithic walls may enhance the potential beneficial properties of coco-crete as follows:

1. Low-carbon material

2. Thermally resistant material (insulating – keeps sun’s heat out)

3. Hygroscopic material (water can go in and out – cooling by evaporation)

4. Uses locally available waste natural fibre (benefits people and planet)

5. Can be crushed and safely added to soil/landfill (recyclable by decomposition)

If anyone can help us to substantiate or disprove these claims we’d like to hear from you.


We have been using coco-crete on a community project at Tinangol near Kudat in Sabah.

Edited by JamesMusslewhite
  • Like 1

Share this post


Link to post
Share on other sites
JamesMusslewhite

So the use of coconut fiber and a lime additive that closely resembles hempcrete seem like a possibility. It could even be made in 1"X4'X8' sheets and be used as interior wall board and exterior siding and nailed or screwed directly to the wood framing as one would use sheetrock (gypsum board) or exterior t1 11 siding plywood. It is flexible and does not crack during earthquakes, stronger than hollow block and concrete, last hundreds of years, fire retardant, and has insulative properties as well as resist humidity. There are some bright members on this forum many with years of home construction properties. So what are your views on hempcrete and coco-crete?

Share this post


Link to post
Share on other sites
JamesMusslewhite

Here is a site of a business in Quezon City that manufactures a coconut fiberboard that can be used to make furniture or for building homes.

 

http://www.mixph.com/2008/08/manufacturing-process-of-coconut-fiberboard.html

  • Like 1

Share this post


Link to post
Share on other sites
CardiacKid

So the use of coconut fiber and a lime additive that closely resembles hempcrete seem like a possibility. It could even be made in 1"X4'X8' sheets and be used as interior wall board and exterior siding and nailed or screwed directly to the wood framing as one would use sheetrock (gypsum board) or exterior t1 11 siding plywood. It is flexible and does not crack during earthquakes, stronger than hollow block and concrete, last hundreds of years, fire retardant, and has insulative properties as well as resist humidity. There are some bright members on this forum many with years of home construction properties. So what are your views on hempcrete and coco-crete?

The idea of using fiber to increase the flexibility of the 1X4X8 sheets is proven technology. When I worked for British Plaster Board one of our products was an exterior sheathing that combined chopped strand fiberglass with gypsum and a polymer to produce a board that was rated as lasting 100 years with no paint applied to the exposed surface. The only problem I could foresee with using it for interior walls would be the smoothness of the surface. That might be achieved using plaster or a skim coat of cement. Looks like an excellent idea to me.

  • Like 1

Share this post


Link to post
Share on other sites
Denis

James,

 

I knew a guy in Australia who was an old fashioned master plasterer.

 

He built his home back in the 1960's with conventional timber frame but the walls were plastered concrete onto chicken wire with a hessian backing support for the concrete 'plaster' to bed onto (concrete was applied after wetting the hessian to effect maximum shrinkage).

 

The other 'old' method is lath and plaster which you could effect with bamboo strips for laths. The good plaster used to have horse hair in the mix!

 

I have done a bit of research on the use of abaca fibres and was interested to see that Mercedes had trialled its use for selected components in their cars (they funded a trial vertical production program in the Phils).

 

I agree that the concrete monolithic structures here do not seem to age well.

Share this post


Link to post
Share on other sites
JamesMusslewhite

Abaca (banana family) fibers also caught my eye because I know it is used to manufacture rope, rugs, and garnishments for shoes. It is widely grown in the Philippines. In the videos and articles I have read they mention a lime based bonding agent. This is still a bit of a mystery as to the composition of this bonding agent? I know that they are using hydrated lime, but as a good friend of mine who is an engineer told me yesterday that there is no chemical reaction in hydrated lime to make the lime properly harden. As a horticulturist and a commercial landscaper it was a common practice to apple lime to soils to swing acidic pH towards a more alkaline pH. The south Texas humidity is higher than here in the Philippines and sakes of lime would harden solid but could easily be crumbled back into power to be used. Because of this I know that just adding water will not permanently harden lime, so there has to be a catalyst added. This catalyst is never mentioned. I know that calcium is used as a hardener as well as cement, but cement is not mentioned in non of the hempcrete videos. So as of now I must still try to further research various materials that will interact with hydrated lime to be a catalysis capable of permanently hardening the lime while allowing the desired flexibility needed to keep sheets and walls from cracking when stressed during earthquakes or typhoon storms..    

Share this post


Link to post
Share on other sites
hyaku

How about termite damage with these blocks? Just wondering how they would fare in termite city.

Share this post


Link to post
Share on other sites
fred42

Interesting stuff..

I`ll be doing something similar for a perimeter wall except Im using a rice husk portland mix which is free and plentiful just about anywhere in the R.P..

  • Like 1

Share this post


Link to post
Share on other sites
Knowdafish

Interesting stuff..

I`ll be doing something similar for a perimeter wall except Im using a rice husk portland mix which is free and plentiful just about anywhere in the R.P..

 

Is the rice husk you are using carbonized or not? Carbonized rice husk can be used as a replacement for concrete to a point without losing any strength, but not plain rice husks.

  • Like 1

Share this post


Link to post
Share on other sites
JamesMusslewhite
@ fred42,
 
Making Carbonized Rice Husk is easy to make and only takes 1-2 hours.

 

 

 

How to make your own carbonizer

 

Edited by JamesMusslewhite
  • Like 1

Share this post


Link to post
Share on other sites
AlooGobi

The guy in the youtube  program below uses GRC glass reinforced concrete in his build,which is shown briefly around the 11.14 mark on the video.

There is some really interesting design ideas in his build if you wish to watch the entire episode

sorry the vid quality is not the best

http://www.youtube.com/watch?v=FnBuA50IL2c

  • Like 2

Share this post


Link to post
Share on other sites
Alan S

Back in the 90's, I did some work there that involved a Manila company that had developed a poanel building system, the panels being made form, concrete mixed with... and hear my memory fails me.

Some natural and local product, is all I can recall.

 

They were superb..

In fact I brought  a small panel back to the UK, and via a friend it went to one of our testing labs who confirmed that it was water, heat  and vermin proof, had superb strenght, long life, and was an ideal building material.

And cheap.

 

Now if I could just rememebr the name.....

 

 

However, it does show that there are good alternatives to the conventional, and that they might be worth seeking out.

  • Like 1

Share this post


Link to post
Share on other sites
JamesMusslewhite

"Hemp building boosters claim that hempcrete foundation walls are up to seven times stronger than those made of concrete, half as light and three times as elastic. This superior strength and flexibility means that hemp foundations are resistant to stress-induced cracking and breaking, even in earthquake-prone areas. The building material also is self-insulating; resistant to rotting, rodents and insects; and fire proof, waterproof and weather resistant."  http://www.hemp.org/news/hempcrete-hemp-building-materials

Share this post


Link to post
Share on other sites
Guest
This topic is now closed to further replies.
Sign in to follow this  

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use, Privacy Policy and Guidelines. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue..