Abstract: In response to the problem of reduced durability of concrete structures in the northwest region of China under salt frost erosion, this study selected concrete specimens with different polypropylene fiber contents (0, 0.6, 0.9, 1.2, 1.5 kg·m^-3) and placed them in clear water, 3%NaCl, and 5%Na₂SO₄ solutions for freeze-thaw cycle testing. The changes in mass loss rate, dynamic elastic modulus and compressive strength of specimens were analyzed, and standard models were established based on Weibull theory and grey theory to predict the maximum service life of polypropylene fiber reinforced concrete structures. At the same time, SEM was used to analyze the mechanism of polypropylene fiber reinforced concrete. The results show that the damage caused by clear water freeze-thaw conditions to concrete is lower than that caused by salt freeze-thaw erosion, with chloride salt causing the most severe erosion damage to mechanical properties of concrete. The infiltration of polypropylene fibers can effectively slow down the degradation rate of mechanical properties of concrete under freeze-thaw erosion and weaken the impact of external erosion on compressive strength. The optimal effect is achieved when the fiber content reaches 1.2 kg·m^-3. The life prediction results of grey prediction model and Weibull model are roughly similar. The grey prediction model can only make large-scale inferences based on data currently contained, while Weibull model has more accurate prediction results. This result can provide theoretical guidance and basis for studying the mechanical properties of concrete and selecting the best model to predict the service life of concrete.

Key words: concrete, polypropylene fiber, Weibull model, grey prediction model, durability, life prediction