Concrete structures located in environments such as oceans, salt soils, and salt lakes are not only subjected to the sustained action of loads, but also to the erosive attack of sulphate ions at the same time, leading to changes in their mechanical properties. This paper focuses on the development of the mechanical properties of fly ash concrete over time, targeting axially compressed fly ash concrete components in a sulfate erosion environment. Under a stress level of 20 %, the paper takes into account factors such as fly ash contents of 25 %, 50 % and 75 %, loading ages of 28d, 90d and 120d, and sulphate solution concentrations of 2 %, 6 % and 10 %, respectively, conducting experimental research on the evolution of mechanical properties after the coupling effects of sustained load and sulfate erosion. Subsequently, the mechanism and law of evolution of axial compressive strength and modulus of elasticity of fly ash concrete after sustained loading coupled with sulphate erosion are analyzed. By using the concrete Compressible Packing Model (CPM) and the Triple-Sphere Model (TSM), along with a durability analysis of fly ash concrete under sustained loading, the calculation models of axial compressive strength, as well as the elastic modulus of fly ash concrete after the coupled action of sustained loading and sulphate erosion are established respectively. Finally, the model established in this paper is evaluated through data analysis using deviation analysis, the Root Mean Square Error (RMSE) and Mean Absolute Error (MAE) methods, comparing it with existing models and experimental results. The research results show that, in terms of deviation analysis, the model established in this paper has a deviation of less than 1.5 % compared to the test data for elasticity modulus, and a deviation of less than 2 % compared to the test data for compressive strength. In terms of Root Mean Square Error (RMSE) and Mean Absolute Error (MAE), the model's errors compared to the experimental results for elasticity modulus and compressive strength are within 0.5. The comparison shows that the calculation results of the mechanical properties model of fly ash concrete constructed in this paper are in good agreement with the test data. The significance of the research lies in its ability to provide a theoretical basis for understanding the long-term performance development law of fly ash concrete structures in sulphate erosion environment.

来源平台：CONSTRUCTION AND BUILDING MATERIALS