Cross-Laminated Secondary Timber: Experimental Testing and Modelling the Effect of Defects and Reduced Feedstock Properties

Abstract

The construction industry creates significant volumes of waste timber, much of which has residual quality and value that dissipates in conventional waste management. This research explored the novel concept of reusing secondary timber as feedstock for cross-laminated timber (CLT). If cross-laminated secondary timber (CLST) can replace conventional CLT, structural steel and reinforced concrete in some applications, this constitutes upcycling to displace materials of greater environmental impacts. The fabrication process and mechanical properties of CLST were tested in small-scale laboratory experiments, which showed no significant difference between the compression stiffness and strength of CLST and a control. Finite element modelling suggested that typical minor defects in secondary timber have only a small effect on CLST panel stiffness in compression and bending. Mechanically Jointed Beams Theory calculations to examine the potential impacts of secondary timber ageing on CLST panels found that this has little effect on compression stiffness if only the crosswise lamellae are replaced. Since use of secondary timber to make CLST has a more significant effect on bending stiffness, effective combinations of primary and secondary timber and their appropriate structural applications are proposed. The article concludes with open research questions to advance this concept towards commercial application.

Understanding forest-based value creation in a regional context

“…Valorisation strategies include reuse to maximise the lifespan of the resource, recycling and energy recovery, following the principles of cascading use of biomass. However, there are also differences in reuse: the potential for carbon sequestration is highest in structural building constructions (Rose, Bergsagel et al 2018). Therefore, there is a clear difference between reusing secondary timber in structural applications and using them as resource for particle boards.…”

“…The recycling of construction and demolition wood waste to produce particle boards was tested and the test results showed that such resources can be used as a resource for the inner layer of medium density particle boards (Azambuja, de Castro et al 2018). Recently UK researchers tested in small-scale laboratory experiments the recycling of secondary timber in the production of cross-laminated timber (CLT) (Rose, Bergsagel et al 2018). The tests were promising but further tests are necessary, and the researchers suggested to combine CLT from primary timber and CLT from secondary timber in structural applications (Rose, Bergsagel et al 2018).…”

Feasibility of cross-laminated secondary timber

“…Their work considered sourcing the timber from existing buildings, but they chose instead to explore pilot manufacture and mechanical testing of ICLT using standing trees that have been affected by pine bark beetle (Wilson 2012). The present authors conducted preliminary research to explore the technical feasibility of using secondary timber to produce CLST (Rose et al 2018).…”

“…The fabrication process and mechanical properties of CLST were tested by the present authors (Rose et al 2018) in small-scale laboratory experiments. These showed no significant difference between the compression stiffness and strength of CLST and a control.…”

“…As a pilot research project, the findings from Rose et al (2018) stimulate further research questions to advance the concept of CLST towards commercial application through additional laboratory-and pilot-scale experiments and modelling:…”