Study on the durability and microstructure evolution of modified concrete in high altitude cold region

Abstract

The cold and high-altitude regions are characterized by low air pressure, intense solar radiation, pronounced freeze-thaw cycles, and salt corrosion. For instance, the damage to concrete roads, culverts, and piers in the Tanggula area of the Qinghai-Tibet Plateau highlights the susceptibility of concrete structures in such regions to premature failure, thereby threatening the long-term safe operation of engineering projects. To enhance the service performance of concrete structures in high-altitude cold environments, this study proposes a novel approach involving the surface modification of basalt fibers using 3-glycidoxypropyltrimethoxysilane and nano-silica. The degradation characteristics of the material's mechanical properties, pore structure, and durability were systematically investigated through various characterization techniques, including apparent morphology analysis, compressive strength testing, relative dynamic elastic modulus measurement, scanning electron microscopy, and mercury intrusion porosimetry. Furthermore, the fractal dimension and KHSi-BF contribution rate were introduced to establish a damage prediction model, thereby improving the accuracy of damage assessment. The results demonstrate that KHSi-BF-N2B2 exhibits superior mechanical properties and durability compared to ordinary Portland cement (OPC) under low-pressure curing conditions. Upon incorporation of KHSi-BF, the particle size distribution of nano-silica becomes more uniform, dispersion is enhanced, and agglomeration is significantly reduced. This improves the interfacial bonding between KHSi-BF and the matrix, leading to increased compressive and tensile strengths, as well as enhanced durability. Compared with other specimens, KHSi-BF-N2B2 features fewer harmful pores and a denser microstructure. The KHSi-BF-SiO₂ cementitious system demonstrates enhanced resistance to solar radiation, freeze-thaw cycles, and salt corrosion. This research provides valuable insights and serves as an important reference for addressing the deterioration challenges faced by concrete structures in alpine and high-altitude regions.