The aging behavior of Moso bamboo in natural weathering condition

Bamboo, recognized as an innovative green building material, is extensively utilized in practical engineering, with its durability in outdoor environments being of paramount importance. The internodes and nodes of bamboo collectively form the primary structure of the bamboo culm, exhibiting significant differences in their structural composition and fracture behavior. In this study, moso bamboo internodes and nodes were exposed to an outdoor environment for two years to investigate their aging mechanisms. The discoloration, dimensional stability, mass loss, and water absorption characteristics of weathered bamboo were assessed through physical property tests. Changes in the microstructure, cellulose crystallinity, and internal crack morphology of bamboo resulting from natural weathering were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and computed tomography (CT). Ultimately, the durability of moso bamboo was assessed based on the results of compressive tests. The results indicated that natural weathering could degrade lignin and hemicellulose on the surface of bamboo, disrupt the microstructure of vascular bundles and parenchyma cells, and impair cellulose crystallinity, leading to a reduction in mechanical properties. Moreover, compared to bamboo internodes, bamboo nodes exhibit a more complex fiber morphology. The presence of internal transverse fibers can significantly impact its compressive property parallel to the grain, but the enhanced spatial locking effect can also improve its durability perpendicular to the grain. This study enhances the understanding of biomass materials and provides valuable insights into the application of bamboo in outdoor environments.