CHEN Huanyong ^{1, 2}, YAO Zhi’an ^{1, 2}, JIA Shuaide ³, KANG Dawei ³, MIN Liang ⁴,
LI Jia ⁵, MENG Qingkun ³, QI Jiqiu ³
(1. Guangdong Provincial Highway Construction Co., Ltd., Guangzhou 510699, Guangdong, China; 2. Shenzhen-Zhongshan Corridor Management Center, Zhongshan 528400, Guangdong, China; 3. School of Materials Science and Physics, China University of Mining and Technology, Xuzhou 221116, Jiangsu, China; 4. Jiangsu CUMT Dazheng Surface Engineering Technology Co., Ltd., Xuzhou 221000, Jiangsu, China; 5. Jiangsu Dazheng Zhi'an Technology Co., Ltd., Nanjing 210036, Jiangsu, China)

Extended Abstract: [Background and Purpose] The construction of large-span steel suspension bridges has increased demand for fire protection materials that can withstand the harsh conditions, including potential fires and humid environments. Traditional fire protection materials often fail to meet the specific requirements of bridge cables, such as lightweight, flexibility and maintaining performance in humid conditions. Fiber-reinforced SiO₂ aerogel composites offer a promising solution, due to their superior thermal insulation and mechanical properties. However, the long-term performance of these composites under hygrothermal aging conditions, which are critical for their application in bridge cables, remains unexplored. This study was aimed to address this issue by evaluating the hygrothermal aging behavior of fiber-reinforced SiO₂ aerogel composites, thus predicting their service life in natural environments.[Methods] Three types of SiO₂ aerogel composites were prepared, with glass fiber, glass fiber-basalt fiber composites, and basalt fiber as matrices, by using sol-gel technology and supercritical ethanol drying processes. The composites were subjected to hygrothermal aging tests at 60 ℃ and 90% relative humidity for up to 180 days. Microstructure, mechanical properties and thermal insulation performance of the composites before and after aging were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), universal testing machine and thermal conductivity measurements. The degradation of mechanical and thermal insulation performance was analyzed, while a prediction model for the service life of the composites under natural environmental conditions was proposed based on the Hallberg-Peck model.[Results] It is found that the fiber was bonded with the aerogels well in the initial state of the composites, with aerogels uniformly filling the fiber-formed framework. After hygrothermal aging for 180 days, some fibers detached from the aerogel, leading to partial fracture of the aerogel blocks. The tensile strengths of the glass fiber/aerogel composite, glass fiber-basalt fiber/aerogel composite and basalt fiber/aerogel composite decreased by 4.9%, 11.7% and 10.3%, respectively, while their thermal conductivities increased by 5.6%, 9.2% and 8.4%. The Hallberg-Peck model was used to predict the service life of the composites in Guangzhou natural environments, while the failure criteria was set to be that the degradation of tensile and heat insulating properties was no more than 10%. As a result, the predicted service lives of the glass fiber/aerogel composite, glass fiber-basalt fiber/aerogel composite and basalt fiber/aerogel composite were 18.7 years, 10.4 years and 11 years, respectively.[Conclusions] The three types of fiber-reinforced SiO₂ aerogel composites exhibit sufficiently high stability and performance retention under hygrothermal aging conditions, making them suitable for long-term service in the humid environments of bridges. These composites showed significant potential in the application on bridge cable fire protection, contributing to enhanced safety and durability of bridge structures. The findings also provide valuable insights into the design and optimization of fiber-reinforced aerogel composites for various engineering applications, highlighting the importance of understanding the aging mechanisms and predicting the service life of such materials.
Key words: bridge fire protection; aerogel composites; damp heat aging; tensile strength; thermal insulation performance