Study on erosion resistance experimental and mathematical modeling of nano-silica concrete in gravelly Gobi windy area

The coarse sand-gravel surface characteristic of the Gobi region generates unique wind gravel flow (WGF) phenomena under the influence of high wind velocities. The multi-grain-size mixing properties of this flow result in significant erosion damage to concrete surfaces, thereby exacerbating the degradation of concrete structures. In order to address the problem of erosion damage to concrete structures caused by WGF, in this study, nano silica (NS)-modified technology was employed to effectively enhance the pore structure of concrete through its dual mechanisms of action: microporous filling and the pozzolanic reaction. The experimental parameters were set to simulate large wind speeds and large particle sizes, making the conditions more representative of the WGF environment in the Gobi region. This study systematically reveals the damage evolution pattern of NS-modified concrete under such WGF conditions. The results indicated that when the NS content was 1%, the erosion rate (ER) of the concrete was reduced to the greatest extent, by 71.8%, thus achieving the optimal erosion resistance at this dosage. The results prove that the ER for NS-modified concrete increase steadily with higher erosion angle, erosion velocity, and gravel flow rate. At low erosion angle, the concrete surface mainly undergoes scratching due to the cutting action of sand and gravel. In contrast, at higher erosion angle, the concrete surface endures more direct impacts from sand and gravel, leading to the formation of erosion pits. The ER of NS-modified concrete exhibited a decreasing trend with the increase in erosion particle size. In comparison to the 0.25–0.5 mm particle size range, the ER of the concrete was reduced by 26.1%–65.5% when the gravel particle sizes were in the 3–5 mm range. The erosion induced by individual large-grained gravel particles resulted in a more extensive and deeper erosion pit. In addition, the ER of NS concrete showed a strong negative linear correlation with its mechanical properties. An erosion model specific to NS concrete in the windy Gobi region was developed by incorporating factors of NS admixture and particle size based on the classical theoretical erosion model. This model offers a scientific foundation for assessing the erosive durability of concrete structures in the Gobi region.