Effect of wind-sand erosion on frost resistance durability of hydraulic engineering concrete in cold irrigation area

Abstract: In view of the actual situation of the concrete service environment of agricultural hydraulic engineering in the Yellow River irrigation of Inner Mongolia, due to the natural river sand becoming scarce, increasing the utilization efficiency of the local aeolian sand resources and using aeolian sand to form aeolian sand concrete meet the requirements of concrete in agricultural engineering and hydraulic engineering. The effect of wind-sand erosion on the frost resistance of aeolian sand concrete in cold irrigation area was studied. The replacement of natural river sand with the aeolian sand of quality substitution rates of 20%, 40% and 60% can be used to compose the aeolian sand concrete, the 28-day cube compressive strength of the aeolian sand concrete meets the C40 requirements. Using self-made sand-carrying flow erosion test device, the actual wind-sand environment in cold irrigation was simulated, including wind speed of 31 m/s, sand carrying capacity of 30 g/min, attack angle of 90° and erosion time of 10 min, and under these wind erosion parameters, the wind-sand erosion test of concrete was carried out. Two different test conditions were designed, i.e. the concrete frost resistance test and the concrete frost resistance test under the influence of wind-sand erosion. The mass loss rate and the relative dynamic modulus were used to evaluate the pros and cons of frost resistance test and the frost resistance test under the influence of wind-sand erosion, the super-depth three-dimensional topography of microscope was used to observe the concrete surface morphology under 2 different test conditions, and the bubble spacing device was used to test the bubble characteristic parameter of hardened aeolian sand concrete under 3 different substitution rates of aeolian sand. The results show that the quality loss rate can not accurately judge the effect of the freeze-thaw damage of aeolian sand concrete under the influence of wind-sand erosion, but the relative dynamic elastic modulus can accurately characterize the freeze-thaw damage of aeolian sand concrete under the influence of wind-sand erosion. Through the relative dynamic elastic modulus, it can be seen that the internal damage of aeolian sand concrete after freeze-thaw cycles under the influence of wind-sand erosion is 2 times that after freeze-thaw cycles without wind-sand erosion. Under the influence of wind-sand erosion, the aeolian sand concrete paste is crisped in the process of freeze-thaw cycles. At the same time, under the continuous impact of the wind-sand flow, the crisped cement paste peels off, and hence eventually the interface transition zone between cement paste and aggregate of destruction surface is more smooth. The aeolian sand with the quality substitution rate of 40% can be prepared to meet the requirement of frost resistance of aeolian sand concrete in cold irrigation area. The bubble spacing factor of hardened aeolian sand concrete can not accurately evaluate the frost resistance. The bubble box dimension and fine aggregate fineness modulus can reflect the bubble structure and fine aggregate grain gradation, and the two are associated and the combination of the two can be used to determine the durability of aeolian sand concrete.