Abstract:

Objective: This study investigated the variations in microstructure and primary chemical constituents of surface timber in ancient architecture during natural aging processes. The aims of this study are to elucidate the correlation between the deterioration severity of load-bearing wood components and chemical degradation, quantify the differences in the degree of deterioration of wood components on different floors, providing a scientific basis for the conservation and restoration of ancient wooden architectural components. Method: Forty-eight samples of historically aged timber taken from the main load-bearing wooden components of the Holy Mother Hall at Jinci Temple were used as the experimental material, with one contemporary reference sample as the control. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) were used to analyze the changes in wood micromorphology, chemical functional groups, and cellulose crystallinity. Additionally, the quantitative content of cellulose, hemicellulose, and lignin was determined and analyzed following the U.S. Department of Energy (NREL) standard protocol. Result: The surface timber of the load-bearing wooden components in the ancient architecture of the Holy Mother Hall has deteriorated to varying degrees, which was correlated with internal cellular damage modalities including bordered pit cracking, cell wall distortion, and structural fragmentation. Concurrently, cellulose, hemicellulose, and lignin underwent degradation in aged timber, with hemicellulose decomposition demonstrating being the most significant. Conclusion: Lignin content in historically aged timber exhibits a progressive increase with advancing cellular deterioration, whereas cellulose and hemicellulose contents demonstrate monotonic decline. There is a statistically significant positive correlation between cellulose content and its crystallinity index. Second-floor structural members in the Holy Mother Hall consistently exhibit heightened degradation of primary chemical constituents compared to first-floor counterparts.

Key words: historically aged timber in architectural heritage, scanning electron microscope (SEM), chemical composition test, Fourier transform infrared (FT-IR) spectroscopy test