The soil and groundwater in the northwest region of China contain high concentrations of Cl-, SO42- and Mg2+, and the aggressive ions will penetrate into the tunnel lining concrete, seriously threatening the service life of the concrete structure. In this paper, orthogonal tests were used to investigate the effects of water-cement ratio, silica fume mixing amount and fly ash mixing amount on the performance of lining concrete. In order to better simulate the actual environment, five different types of composite salt solutions containing Cl-, SO42- and Mg2+ were prepared, and the optimal combination of factors in the orthogonal test was selected to carry out a study on the change rule of the compressive strength and the chloride concentration in the surface layer after 56 days of erosion, and the micro-analysis of the erosion process was carried out by using Scanning Electron Microscope (SEM) and X-ray diffraction (XRD). The results show that the mechanical properties and anti-chlorine ion erosion performance of lined concrete are best when the water-cement ratio, fly ash dosage, and silica fume dosage are 0.33, 30%, and 8%; when the concrete is under the joint action of Cl- and SO42-, the expansion of the hydration product calcite destroys its internal structure, which results in the decrease of the compressive strength and the acceleration of the rate of Cl- invasion; and under the joint action of Cl- and Mg2+, the Mg2+ invasion will destroy the alkaline environment inside the concrete, which will also cause the reduction of compressive strength, but its product Mg(OH)2 will hinder the invasion of Cl- into the interior of the material. When Cl-, SO42- and Mg2+ act together, Mg2+ and SO42- can inhibit the erosion rate of Cl- to different degrees, respectively, while SO42- and Mg2+ exist in a compound effect of mutual inhibition, which makes it possible to effectively reduce the loss of compressive strength of concrete.
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