Mechanisms of fire resistance deterioration in chinese fir induced by environmental aging

Abstract

Chinese fir, commonly used in ancient Chinese architecture, is prone to aging due to prolonged exposure to environmental factors such as UV radiation, temperature fluctuations, and salt spray. This aging process not only alters its microstructure but also significantly weakens its fire resistance, potentially compromising the safety of cultural heritage. To investigate the specific impact of environmental aging on the deterioration of fire resistance in Chinese fir, accelerated aging experiments involving UV aging, high-low temperature cycling, and salt spray erosion are conducted. The results indicate that UV radiation induces lignin degradation in the wood, resulting in an increased heat release rate (HRR) peak to 171 kW/m². High-low temperature cycling results in the formation of microcracks in the wood, causing the peak smoke temperature to reach 88.6 kW/m². During salt spray erosion, the catalytic effect of Cl^- promotes polysaccharide hydrolysis, which facilitates the formation of dense carbon, reducing the HRR peak to 112 kW/m². Additionally, the three-level correlation model is established to link environmental stresses, microscopic damage, and combustion reactions. This model reveals the cross-scale causal chain of Chinese Fir, from macro-environmental factors to microscopic damage, and finally to its combustion behavior. This analysis provides an in-depth examination of how various environmental factors influence the fire resistance properties of wood by altering its microstructure, offering a theoretical framework for investigating the aging process of wood materials and enhancing fire resistance performance. It is especially applicable to the preservation and safety assessment of ancient architecture's wooden materials.