Dutch-grown and secondary timber in cross-laminated timber (CLT): An experimental and analytical study

The Netherlands aims to use 30 % biobased materials in 30 % of the new constructions by 2030. Currently, most structural timber is imported, adding costs and transportation emissions. Therefore, studying the structural potential of local sources, such as secondary and Dutch-grown timber, is essential. While the reuse of reclaimed timber from deconstruction has challenges, its availability, similarly to Dutch-grown timber, will increase, potentially offering structural capacities. Laminated timber can enable optimal use of virgin and secondary timber, enhancing biobased construction. Thus, the structural potential of circular cross-laminated timber (c-CLT) panels made from Dutch-grown and secondary timber is studied. Five-layered c-CLT panels made from Dutch-grown Ash, Douglas, and secondary Spruce (cross-layers) were produced. The laminates were graded using stress-wave analysis, providing input for an analytical model to predict the c-CLT performance. The c-CLT panels were tested in bending and planar shear, combined with Digital Image Correlation (DIC), to study their structural potential and validate the analytical model. The c-CLT exhibited 3 % higher stiffness and 36 % higher strength in bending compared to commercial CLT, and the strength was equal in planar shear. A good match was found between the analytical model’s prediction and the DIC data in bending and shear, confirming the model’s performance. Predicted c-CLT properties, such as bending and shear stiffness and failure load, matched the experimental values. In conclusion, the c-CLT panels exhibit competitive mechanical properties to commercial CLT, and the performance is accurately predicted using the properties of the laminates and analytical modeling.