To reveal the flexural behaviour and microproduct evolution mechanism of FRG cemented aeolian sand, four factors, namely, sodium hydroxide dosage, water-solid ratio, fibre dosage, and fibre length, were classified into mutually independent levels and combined to form a set of test matrices for the design of orthogonal tests. Using DIC digital scattering technology to analyze the evolutionary process of specimen ring-breaking and employing scanning electron microscopy to explore the polymerization product micro-morphology, evolutionary process, pore defects, and analyze the fiber endowment morphology and the destruction mode; the use of EDS spectroscopy, X-ray diffraction, Fourier IR spectroscopy, and other technical means to analyze the polymerization product chemical composition, elemental distribution, and evolutionary characteristics. The results of the study show that the 28-day flexural performance of FRG cemented wind-blown sand as a filling material is significantly affected by various factors in the following order of magnitude: sodium hydroxide dosage > water-solid ratio > fibre dosage > fibre length. The optimal combination from the local test is: sodium hydroxide dosage of 1.4 %, the water-solid ratio of 0.32, the fibre dosage of 0.5 %, and the fibre length of 12 mm. With the increase in load, the value of the displacement field increases continuously, indicating a greater degree of specimen damage. As the reaction proceeds, the polymerization product's morphology evolves from rod-like to flaky, ultimately stabilizing into a network structure. The main elements in the product include C, O, Si, Al, and Ca, indicating that the polymerization product is a C-(A)-S-H gel. A reasonable distribution of discrete ductile fibers can play a positive role inside the specimen, acting as a bridge. The damage behavior under bridging can be divided into fiber debonding, producing slippage behavior, and fiber damage, leading to fracture behavior. The results of the study provide a scientific basis for the design, preparation, and application of solid waste filling materials, thereby promoting the development of materials science and engineering.
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