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Beetlecrete: Concrete solution for beetle kill wood
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Combining the characteristics of concrete and wood, Beetlecrete has the potential to be used for making a backyard bench or rebuilding an earthquake-torn country.


Sorin Pasca developed the material he calls Beetlecrete at UNBC (University of Northern British Columbia) in Prince George in 2007 and it earned him his master's degree.

Using a blend of wood chips, cement and water poured into molds, he created a hybrid material that can take a nail or screw without pre-drilling and can be cut with regular woodworking tools. It's also water-resistant and stronger than many similar products on the market.

At the time, an article on the UNBC website said the research "was of tremendous value to the BC forest industry, which is seeking alternative wood products to complement the production of dimension lumber, plywood, wood pellets, and oriented strand board."  It is also a way to use mountain pine beetle wood that can't be used by lumber mills because of its cracking tendency. 

Today, Beetlecrete is still in development but, says Pasca, not at the rate he expected. The severe downturn in the forest industry over the last two years may have a lot to do with that, dampening the initial excitement about the product where funding was concerned. Pasca has been trying to move the product out of the lab and into small scale manufacturing by partnering with a shop in Prince George to make real size applications.

He is also developing a series of workshops, presented as continuing education at UNBC, to share his knowledge and enthusiasm with the public.

"It's the easiest way to promote development - let everybody experiment with it, let people start making applications," says Pasca.

There will also be a website, www.beetlecrete.ca, to promote the workshops and share discoveries.

So far, applications of Beetlecrete include countertops, at the Local Government House of the Union of BC Municipalities in Victoria, B.C. and at the Ramada Hotel in Prince George, and a bench at the UNBC campus. At his own home, Pasca has stair treads that test the material's abrasive resistance in a flooring application. Outdoors, he has garden blocks and stepping stones that have weathered four Prince George winters without cracking.

Characteristics
"Wood cement composites have been developed for more than a century but in North America there's not a real market for wood cement boards," says Pasca. "In Europe, the products come as boards made by pressing like OSB or plywood. Beetlecrete is a moldable product made with just cement and wood, "green" and free of petroleum based binders."

To make Beetlecrete, Portland cement powder and wood chips are combined with water. The wood replaces the sand or gravel aggregate normally used. Like concrete, the material can be made into shapes using concrete forms or molds. 

"It's a hybrid between concrete and wood particle board so it takes properties from both sides," explains Pasca. "The concrete gives it moisture resistance, so, for example, you can soak it in water for 2 weeks and nothing happens. It won't swell. It's also fire resistant because of the cement matrix covering the wood chips." On the other hand, Beetlecrete can be worked just like particle board, since wood replaces the aggregate in concrete while cement acts as a binder.

Recipe
"There's no sole recipe because wood is so variable in its nature," says Pasca. "I develop a formula based on the type of wood I'm using, the shape of the particle, the size, how well the particles are arranged. Also, I look at the wood's permeability for determining the right consistency of the mixtures. It definitely needs more water than making ordinary concrete where the mineral aggregate is impermeable. You need enough water to complete the cement hydration but too much water could also ruin the quality of your concrete. ”

Regarding the wood species, "Lodgepole pine is the best available in North America," says Pasca. "Because wood is an organic material it inhibits cement hydration. Some wood species are more compatible than others - based on the level of extractives, the type of chemical components, etcetera - and Lodgepole pine works the best."

But Pasca wanted to see what happened with the beetle kill Lodgepole pine and found it's even better. "Weathering of these dead trees which stand in the forest for so many years possibly extracts or volatilize whatever inhibits cement. It’s almost like a mineralization process."

There are many methods of making the wood more compatible, "or rather reducing its incompatibility," says Pasca.  He uses an innovative process that improves the chemical compatibility and also reduces the permeability of the wood.  "The wood is already compatible but I want to make it more stable. It's better for decorative products. But you can still make products without applying any extra treatment to the beetle wood."   

The wood chips don't need to be dried before using. Sorin tests every batch of wood prior to doing a mix and adjusts the amount of water to compensate for variation in moisture content. He grinds and screens the wood before using it to optimize the shape and size of the particles.

Curing time can be up to 28 days. "Curing is keeping the water with the cement, not allowing the water to evaporate, in order to prolong the chemical process of hydration and to increase the strength," explains Pasca. "In this case, the wood is so absorbent it provides the moisture required for curing. It needs more research, but the aggregate could actually be used as a curing agent so you can do curing and drying in the same time."

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