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Growing, Processing, and Building with Hempcrete

January 21, 2021
Hemp Co. Admin

“Hempcrete is the eco-friendly building material of the future”

If you’ve been following for a while, you’ve probably heard or read something along the lines of the preceding statement.  And maybe those who haven’t still have questions.  That’s okay!  We’re here to help answer them.  

Hemp has been overlooked as a solution for practices that cause significant damage to the environment from industries ranging from clothing to construction.  But nowadays, the number of problems that it offers to solve is becoming too great to ignore.  The idea of building houses with a plant may seem a little far-fetched, but today we’re going to dive into why it’s such a viable idea.

Growing Hemp for Hurd

What is Hemp Hurd? 

Hemp Shives, Hemp Hurd, is also derived from the Hemp stalk’s inner woody mass that surfaces once the bast fibre is removed. But wait, doesn’t that make hurd a by-product? Well, even though that is technically true, this low-value agricultural by-product has a lot of practical applications. From being useful in the construction industry to being envisioned as the successor of wood pulp in the paper industry, hemp hurd might just be the next multi-million dollar industry on its own.

You can learn more about Hemp Hurd here!

How To Grow Hemp for Hurd?

First thing’s first, you need to be sure that you choose seeds that have been purpose-bred to increase your crop yield. You also need to make sure that whatever you plant is in compliance with your area’s THC policy or you might just end up losing the entire crop and possibly even face criminal charges. Another consideration would be deciding whether you would prefer planting a seed or a clone.

What’s the difference? First of all, seeds do not necessarily always turn out to be of the same phenotype or quality as their parents. There could be, possibly, more than five different phenotypes resulting from 10 seeds of practically the same variety. 

Planting a clone could save you time and money (in the long run) because you’re working with known and stable genetics and so you’re eliminating most of the risk there and then. Make smart and efficient choices.

The next thing to keep in mind is the climate and soil atmosphere of your plant. Hemp grows in a warm environment and a mildly humid soil atmosphere that receives enough rainfall/irrigation to keep its seeds moist. 

Harvesting and Processing 

Hemp, as a plant, exhibits pretty speedy growth. The crop is usually ready for harvest in 3-4 months after plantation. However, the time may vary if you are growing hemp with a specific harvest in mind. Harvesting timeframes for Hemp Hurd is generally around the same time as hemp fibre, before the last pollen is shed. 

The step that follows harvesting hemp is retting, which happens in one of two ways. You either let the dew work its magic, or you flood the field and let your Hemp soak in it for a few days before allowing it to dry. Different microbial actions will separate the enzymes that bind the fibres to the inner woody stalk, enabling you to separate the stem’s hemp bast. 

The separation marks the end of the retting process. Once retting is complete, the stalks are dried and crushed in a decorticator. A decorticator is an industrial machine that separates the fibres from the dried stalks and collects hurd separately. 

And there you have it! The woody shives are now ready to be stocked up in bales or used.. 

Mixing and Building

Turning Hemp into hempcrete is a series of steps that requires great precision and attention to detail. Here’s what you need to keep in mind:

Binding Agents

Lime based binders (50% lime, 50% metakaolin) can be used to make Hempcrete, mainly because they absorb water and chemically cure the mixture as it is made. A basic Hempcrete recipe is 4:1:1! 4 parts industrial Hemp Hurd, 1 part lime binder and 1 part water.


However, people also use clay and other unfired binders instead of lime ones, personally vouching for the potential cost savings and other benefits of using them.

Mixing

Hempcrete can be made either by using just your hands or a mortar mixer and usually no other sophisticated equipment is required to do the job. 

Almost everyone has a different sequence of adding ingredients. However, the science suggests that dumping the water into the hempcrete mix is the most effective way of adding it. Some people prefer misting the water, but this has shown to be less effective.

The whole process should take around 10 mins. You’ll know that the mix is ready when it is dry enough to retain its shape when packed into a ball yet moist sufficient to crumble when force is added. 

Remember, too much water will impact the drying time once it is made into a wall or concrete structure. Once properly mixed and set (usually takes 20-30 mins), your Hempcrete will be ready to use. 

Making the Wall out of Hemp

Monolithic Cast Walls

This is one of the most commonly used methods of making Hempcrete walls. Also known as the standard-slip form, this method requires that you “cast” Hempcrete in either wooden or plastic structures and tamp around the edges to secure it in its place. This is somewhat similar to pouring concrete while making a traditional wall. However, we use the term “casting” instead of running when referring to Hempcrete. 

The hempcrete will need some time to set, usually a day or two before you can remove the forms and use them for other walls. 

Once completed, allow 6-9 weeks (depending on the climate) for your Hempcrete to dry up to 15% moisture content and take its final form. 

Hempcrete Blocks

Hempcrete blocks are ready-to-use, non-structural, construction blocks that are lightweight, recyclable and pretty sturdy.

They save you the drying time needed for monolithic walls as they are batch-dried at the production facility; however, bear in mind that they are only used for wall-filling or insulation purposes. 

This is because they lack the cohesiveness of monolithic walls, which have no spaces in between and are cast all at once to achieve a seamless consistency. 

Spray-on Hempcrete

This spraying hempcrete method involves the use of an industrial spray for wall-making. Yes! 

You can simply add hempcrete in a cement mixer and let an industrial sprayer build the hempcrete wall from interior formwork instead of manually adding it layer by layer into the form and working your way to the top. 

The main drawback is that this method employs expensive equipment and requires far more practical knowledge of Hempcrete and Hempcrete construction than the traditional method. 

Benefits of Building with Hempcrete

Hempcrete can replace conventional construction materials and provide sustainable and environmentally friendly means of fulfilling our housing needs. Hempcrete greatly reduces the need for using toxic building materials and saves you a ton of money during construction. 

Here are ten reasons why you should prefer to build with Hempcrete:

  • Non-Toxic 
  • Affordable 
  • Durable
  • High Structural Integrity 
  • Insulator
  • Co2 Absorbent
  • Moisture Regulator
  • Mould and Pest Resistant
  • Recyclable
  • Fireproof

Hempcrete absorbs Co2 and other irritants in the air while naturally adjusting the room’s humidity and temperature. This breathable material not only gives you a natural, healthy environment but also drastically reduces your heating/cooling costs.

Being diffusive and moisture-absorbent means that Hemp walls are less likely to be infected with moulds, which also directly equates to lesser allergies, chronic respiratory diseases and asthmatic attacks associated with moulds and their airborne spores.

Our planet’s health takes a toll every time we use cement, wood or toxic chemicals for construction purposes. Thus, the sooner we can incorporate Hempcrete in the construction industry, the bigger part we can play in preserving the environment.

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