Degradation mechanism and life prediction of cemented tailings backfill under dry–wet cycles and salt erosion

In this paper, the effects of drywet cycling and salt erosion on the unconfined compressive strength (UCS), relative dynamic elastic modulus and mass of cemented tailings backfill (CTB) were investigated, and the mechanism for CTB deterioration was explored with scanning electron microscopy-energy dispersive spectroscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The reliability lifespan of CTB was predicted with the Wiener stochastic process. The results showed that with the increases in the number of drywet cycles, the damage to the CTB deepened continuously, including skin peeling, corner damage, and aggregate exposure; the UCS, relative dynamic elastic modulus and mass of CTB immersed in a sodium chloride solution, a sodium sulfate solution, and a solution of both first increased and then decreased; and the UCS, relative dynamic elastic modulus and mass of CTB immersed in a magnesium chloride solution, a magnesium sulfate solution, and a solution of both showed a decreasing trend. Cl- inhibited the erosion of CTB by SO42- but did not inhibit erosion by Mg2+. Cl- and SO42- invaded the CTB to produce calcium hydroxide, gypsum, Friedel's salt, ettringite, C-S-H and other products. The reliable lifetime predicted with the relative dynamic elastic modulus used as the degradation index was the longest, followed by the UCS, and the lifetime predicted with the mass was the shortest.