Temperature effect of tungsten tailings activated by NaOH

The unconfined compressive strength of specimens with three moisture contents and three NaOH/TMG ratios (sodium hydroxide mass/solid mass, where solid contains tungsten tailings, metakaolin and commercial geopolymer) cured at 60–100 ℃ for seven days was conducted to investigate the temperature effect and action mechanism of tungsten tailings strength activated by NaOH. The test results of the scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) were adopted to analyze the micro characteristics of the mixture under different curing temperatures. The test results indicate that the unconfined compressive strength of tungsten tailings activated by NaOH increases first and then decreases with the increase of curing temperature, and reaches the maximum at 90 ℃. C(N)-A-S-H gels mixed with poly-sialate (PS) and poly-sialate-siloxo (PSS) types are generated at different proportions at different temperatures activated by NaOH. The relative content of PS type gels increases when the curing temperature rises from 60 ℃ to 90 ℃, and decreases when the temperature continues to rise to 100 ℃. The greater the total amount of gel and the relative content of PS-type gel, the greater the strength of the specimens. In this study, the unconfined compressive strength is strongest in the temperature of 90 ℃. It was the optimal curing temperature. The minimum and the maximum strengths were 12.4 MPa and 42.8 MPa when the curing temperature is over or equal to 70 ℃, which meets the strength requirements of building bricks of MU10. In conclusion, the research results provide scientific basis and references for the resource utilization of tungsten tailings.