New uses for low-quality US hardwoods

A wood panel is produced at West Virginia University, part of research that focuses on ways to utilise Yellow poplar as a source of engineered wood building material. Pic: WVU Davis College of Agriculture, Natural Resources and Design

What may be considered lower grade West Virginia hardwood lumber can serve as an affordable, sustainable alternative to traditional building materials like softwood, steel and concrete.

Researchers at West Virginia University’s (WVU) Appalachian Hardwood Centre (US) have been testing the effectiveness of Yellow poplar, an abundant species in the state, as a source of engineered wood building material. Yellow poplar grows straight, has small limbs and processes easily, making it well suited for construction.

Half of the hardwood harvested for sawn timber in West Virginia is considered low-quality lumber because it has too many knots and other defects, according to the researchers at the Davis College of Agriculture, Natural Resources and Design. It is used for pallets, boxes, railroad ties and flooring.

While traditional lumber comes as a single piece, it’s possible to create a sturdy, durable product by gluing and pressing multiple pieces together in layers. These large, thick panels are known as cross-laminated timbers (CLT).

CLTs come from lower grade material. They are used for long spans in walls, floors and roofs, and do well as load-bearing elements. The panels are typically manufactured using softwoods — spruce, fir and pine — but not with hardwoods.

Structural applications

The researchers suggest that certain Appalachian hardwoods, like Yellow poplar, work well in structural applications. They liked Yellow poplar because it has been tested extensively in the past for structural applications.

In the lab, the team has created panels of three, five and seven layers using a press that can apply 120 kg of pressure per square inch. The researchers tested the panels’ bending and breaking strength and subjected samples to harsh conditions like water saturation and dehydration.

Tests were performed multiple times also to see if the glue bonds held. Results indicated the panels will perform well in construction.

The next step will be to get Yellow poplar accepted as a permited raw material by the American Panel Association. At that point, CLT manufacturing companies will be able to use Yellow poplar CLTs in commercial construction.

This will be useful not only for the construction industry, but also for the forest product companies throughout Appalachia, where much of the hardwood ends up being used in low-value items.

The potential success of CLT use hinges on a region’s ability to produce them. The panels are difficult to transport – each 3x10-foot panel weighs up to 320 kg – so hardwood manufacturing facilities need to be close to the market to reduce the cost, he said.

Red oak

Researchers are also looking at uses for Red oak, another Appalachian hardwood, in the construction of timber mats, which are wooden structures used to support heavy duty equipment working on sensitive sites.

They are used where soils degrade quickly with traffic, wetland sites and in applications like gas exploration, logging and electrical powerline maintenance.

Timber mats are used in fields to hold up large pieces of equipment. The mats are made predominantly out of Red oak, which outlasts all the other components and can endure harsh climatic conditions.

There are no restrictions or regulations for these mats. They are going to be destroyed after heavy equipment repeatedly runs over them. If these panels are tested and they work effectively, a lot of Appalachian hardwood lumber mills could get into this business by making timber mats using CLT technology.

In addition to economic benefits, CLTs may be useful in crises and humanitarian efforts. They could be put together in a pinch by in any emergency situation where people need housing.



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