The construction sector substantially consumes resources, generates waste, and emits greenhouse gases. Thus, reorientating this sector is crucial. Using wood could serve as a catalyst. Wood stores carbon, positioning it as an eco-friendly building material compared to many alternatives and a sustainable choice for construction. However, we can only unlock this potential by using the wood. Once wood reaches the end of its use, common practice involves incinerating it, which releases the stored carbon into the atmosphere. Thus, keeping wood in long-lasting or sequential applications is essential to maximize its benefits.
Several studies have investigated how to reuse wood by implementing a building design that allows easier disassembly. However, we must also consider situations where the wood is damaged or when the original dimensions need alteration, which might make reuse not an option. This is where the idea of “wood cascading” comes in. Wood cascading is about using wood for different applications, one after the other, with the last step being burning it for energy. Previous studies considered the use of recovered wood in glued building products. However, we still largely do not know the mechanical properties of recovered wood. Other unknown factors are damages due to previous use and aging processes, which can influence the material yield of recovery processes and, thus, if it makes financial sense to do it.
In this study, we asses the potential of secondary lumber for structural applications through visual grading and mechanical testing in Germany. We evaluated the mechanical properties of lumber specimens measuring 30/50 mm, 40/60 mm, and 30/90 mm in cross-section, processed from rafters previously used in buildings. In the current research stage, we try to predict the strength of the lumber through visual inspection in accordance with a German standard (DIN 4074-1:2012-06). In addition to non-destructive methods, we also subject the specimens to bending and tensile tests, stressing them until failure to determine their strength properties.
With a background in civil engineering, I often dealt with construction and demolition waste in my former daily work. Many of the materials appeared to be in good condition, which leads me to think: Why aren’t there better common ways to deal with them instead of just throwing them away? Now, in my PhD studies, I can combine my interests in craftmanship and the structural design of historical buildings with the evaluation of wood technological analyses. I can work on my passions while also contributing to mitigating the climate-related factors of resource consumption, waste generation, and emissions with our research.
Keywords: wood cascading, recovered wood, waste wood, visual grading, mechanical testing
Authors
Florian Böhm
Technical University of Munich, Germany
Sajjad Hossan Jubair
Technical University of Munich, Germany
Andriy Kovryga
Technical University of Munich, Germany
Michael Risse
Rosenheim Technical University of Applied Sciences, Germany
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