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Sulfate attack is a major cause of the deterioration of concrete structures.Accurately predicting the temporal and spatial distribution of sulfate ions in concrete is the basis for revealing the mechanism of concrete performance deterioration caused by sulfate attack. In this article, based on the pore change caused by sulfate damage to cement mortar, a diffusion model of sulfate ions in cement mortar considering changes in surface concentration was established. Furthermore, a two-dimensional mesoscopic concrete model composed of cement mortar, coarse aggregate, the intrafacial transition zone (ITZ) and macroscopic defects, which can reflect the real aggregate shape, was constructed to study the diffusion of sulfate ions in concrete. The correctness of the model is verified with existing experimental data, and the model is further studied. The results show the following. (1) The average value of the calculation results of multiple sets of models can be used to eliminate the influence of the randomness of the construction of the two-dimensional mesoscopic concrete model. ( 2) With increasing stone content, the corrosion depth increases, but the average concentration at a given location decreases. (3) With increasing sulfate solution concentration and water-cement ratio, the sulfate ion concentration and the corrosion depth in concrete increase.

Shear stress is an important index to evaluate the rheological behavior of magnetorheological fluids (MRFs), which is not only related to the properties of the ferromagnetic particles, but also...

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During the construction of tunnel based on drilling and blasting method, a large amount of wastewater will be produced, in which the types and concentrations of main pollutants will change regularly with the continuous circulation of construction process. In this paper, the wastewater of Hengwu tunnel in the drilling, post blasting, slag discharge and initial support stages is sampled and detected, the main pollutant types and change laws of construction wastewater in each stage are analyzed, and the set pair analysis method is used to evaluate the wastewater quality to determine the degree of wastewater pollution in different construction stages. The research shows that after blasting, the concentration of ammonia nitrogen first reaches the peak, and then other pollution concentrations begin to rise. Different construction stages have different effects on wastewater quality. The construction wastewater generated in the initial support stage of Hengwu tunnel is the most polluted, and the construction wastewater in the drilling stage is the least polluted. The research results of this paper can provide reference for the selection of wastewater treatment process in different construction stages of similar projects.