The increasing popularity of cross-laminated timber as a building material has an Arkansas professor working on ways to transform a waste byproduct of CLT production into a construction material itself.
Frank Jacobus, an associate professor at the Fay Jones School of Architecture & Design at the University of Arkansas at Fayetteville, worked with a research team this past year on turning wood byproducts, often called wood flour because of its similarity to the baking flour, into usable building materials. Jacobus said the research is especially relevant now with the surging use of cross-laminated timber panels in several high-profile construction projects in northwest Arkansas.
The highest profile of all is the new home office planned by Walmart Inc. of Bentonville, which said it will use more than 1.1 million cubic feet of mass-timber products, including CLT. A Canadian manufacturer, Structurlam of Penticton, British Columbia, also announced it would invest $90 million in a plant in Conway to produce mass-timber products, prefabricated engineered wood used as structural components in construction.
Jacobus, who holds the 21st Century Chair of Construction & Technology at the school, said using mass-timber products like CLT panels is friendlier to the environment but also produces quite a bit of waste. Anyone who has sawed wood understands sawdust and shavings.
Jacobus’ research, funded in part by a grant from the university’s Chancellor’s Discovery, Creativity, Innovation & Collaboration Fund, attempted to turn wood flour into building material through use of a 3D printer.
“Cross-laminated timber loses about 15% of its matter to waste during production,” Jacobus said. “To me, it is, ‘How do we use byproducts, not just wood?’ Wood is good because it’s a renewable resource and it is already good in the CLT. We want to start using the byproducts. At some point, is there too much byproduct to burn as fuel to make sense? Maybe it becomes an economic engine for companies.”
The early results produced workable wood structures, although one prominently displayed in the lobby of Vol Walker Hall has suffered some breakage of brittle pieces; printing a house isn’t quite feasible yet.
Jacobus said the challenge is to figure out the right mixture of wood flour and binding agents. Right now, the mixture is 60% wood, with the rest water, a smidgen of baking flour and an epoxy resin.
Leaders of the Pack
The architecture school’s interest in mass timber and its flour byproducts shouldn’t come as a surprise, since it has been led by Peter MacKeith since 2014. MacKeith spent nearly a decade as director of the Master of Architecture-International Program at Aalto University in Finland.
CLT has been commonly used in Europe for many years. MacKeith has promoted the teaching CLT techniques at Arkansas. Under his leadership, the school is creating the $15 million Anthony Timberlands Center for Design & Materials Innovation.
“The expressed ambition of this project is to achieve design excellence of the highest quality and to demonstrate innovation in materials and construction, with a particular focus on the potentials of mass timber and wood products,” MacKeith said in a news release announcing the six finalists to design the center.
The state’s interest is also understandable. If there is one thing Arkansas has plenty of, it is pine trees, and the completion of the wood-processing facility in Conway could be a boon for the mass-timber industry.
Arkansas also began growing industrial hemp last year on a much smaller scale. Local builders said that hemp is used to make a concrete-like brick called hempcrete, but it is not ready for construction use anytime soon.
“Mass timber is the next thing that everybody is going to be talking about for the next few years,” said Jason Wright, a partner with the architecture and design firm Modus Studio in Fayetteville. “There isn’t a whole lot else to talk about. Frank Jacobus and those guys are the leaders of the pack relative to exploration.”
Cross-laminated timber panels are slightly more expensive to use than other materials, but part of that expense is related to the scarcity of the product in America. CLT panels have been widely used for years in Europe, but until recently, the only CLT manufacturing facility in the United States was in Oregon.
A facility in Alabama and the one in Conway, when they are up and running, could conceivably make CLT easier to get and cheaper to use.
“The big talk in Arkansas is CLT and the panels, especially with the new CLT plant in Conway,” said renowned Fayetteville architect Marlon Blackwell. “That will give access to other markets for Arkansas and also give access to builders and developers here, because typically you had to go to Alabama or up into Canada. That is a new material that is pretty fantastic.”
The two university projects, a 27,000-SF library storage facility and 200,000 SF of residence halls, used CLT shipped from Austria. The state of Arkansas grows 8 million more tons of yellow pine timber — a prime ingredient in CLT — than it harvests annually, said Matthew Pelkki, chairman of the School of Forestry & Natural Resources at the University of Arkansas at Monticello.
The university’s use of CLT in its two projects created Jacobus’ Eureka moment because it made him think of all that sawdust. What to do with it?
“It’s like using the whole animal,” Jacobus said. “You’re taking the wood and using the byproducts to make other parts of the building. People talk about zero-waste economy and this fits in with that ethos.”
Many builders don’t have the luxury of thinking up new construction materials themselves because their job is to build what the owner wants and the architect designed. “We are just handed a set of plans,” said Cody Crawford of C.R. Crawford Construction in Fayetteville. “It could be built out of toothpicks and we’d do it.”
Holding It Together
Jacobus said the next step in the process is to find a natural epoxy to use in the 3D printing mixture. He is experimenting with rice glue, long used in Japan, and hide glue, which is made from animal carcasses.
Jacobus joked that his nightly routine is cooking white rice, grinding it into a paste and turning it into glue. Too much water and his rice glue falls apart.
“What’s bad about this now is the resin; we don’t want to use an epoxy resin and we don’t want to use formaldehyde-based glues,” Jacobus said. “How do we do what we did here but with sustainable mixtures? The epoxy is not good in the long term. We want to make less of that and we want to make more of the natural stuff.
“My interest is how do we get 100% natural. I want to look at that thing and know it is not doing anything harmful to the environment.”
Jacobus said it’s likely to take years to solve the challenge of turning wood flour into construction material, but it’s a worthy endeavor because the importance of CLT as a building component is likely to grow.
“Mass timber is going to steal the spotlight,” Wright said. “It is a more responsible material for us. If you think about it, the building industry is responsible for a huge footprint in the carbon discussion. We want to find materials that are friendlier to the environment.”
Blackwell said he hasn’t worked with CLT before but he did recently design the CO-OP Ramen restaurant in Bentonville using only “off the rack” plywood sheets. He said the plywood edges were painted, giving the material a more finished look.
“It’s the little dumb things that actually turn out to be kind of smart,” Blackwell said. “We were trying to prove if you take anything ordinary and apply innovation and craft and thought with it, you can make it sing.”