关键词: 水工混凝土, 冻融循环, 硫酸盐侵蚀, 寿命预测, 机器学习模型

Abstract: To study the durability of hydraulic concrete under the environment of freeze-thaw salt intrusion in the northwest region, we prepare concrete specimens with different fly ash dosages and conduct freeze-thaw cycling tests, using different concentrations of sodium sulfate solution as the medium. The tests clarify the specimens’ behaviors under different cycles－appearance, quality, compressive strength, and dynamic modulus of specimens. And a concrete lifespan prediction model is developed based on the XGBoost model, and it is evaluated and validated. The results indicate that as the number of freeze-thaw cycles increases, the quality, compressive strength, and dynamic modulus of concrete gradually decrease; The number of freeze-thaw cycles and the concentration of sodium sulfate solution are the key factors of concrete lifespan. The 8% solution causes the highest degree of damage, and the corresponding rate of concrete quality loss reaches 4.55% after 150 freeze-thaw cycles. The fly ash content has a certain impact on concrete durability; its optimal value is 10% and the resulted quality loss rate is 3.99% after 150 freeze-thaw cycles. The results show the XGBoost model has high accuracy and reliability in predicting concrete lifespan. This study would help the durability design and lifespan predictions of concrete structures.

Key words: hydraulic concrete, freeze-thaw cycle, sulfate erosion, lifespan prediction, machine learning model