DOI: 10.3724/SP.J.1249.2018.01048

Journal of Shenzhen University Science and Engineering (深圳大学学报理工版) 2018/35:1 PP.48-54

Cementation characteristics and freeze-thaw mechanism of fly ash-modified soda residue soils

Soda residue and fly ash are used to synthesize the fly ash-modified soda residue soils for the backfill engineering in order to promote their comprehensive utilization. Cementation characteristics and freeze-thaw mechanism are investigated through the experiments of the boundary moisture content, compaction test, triaxial test, frozen-thawn cycle test, and by the methods of Fourier transform infrared spectroscopy, scanning electron microscope and X-ray diffraction. Results show that the optimum moisture content of modified soda residue soils decreases at first and then increases with the increase of fly ash content. The maximum appears when fly ash content is 50%. The product gel makes the 28 d shear strength of the modified soda residue soils to be the maximum when fly ash content is 50%. The curing time has a significant effect on the frozen mechanism. During the freeze-thaw cycle, calcium (alumino) silicate hydrate gels are frozen at the negative temperature and restore the original cementation at normal temperature. The water migrates to the frozen edge, the micro-cracks are expanding to the internal gradually until the soil sample expands and shear strength decreases. At the same time, some CaSO4 and CaSO4·0.5H2O crystals precipitate under the alternating temperature.

Key words:inorganic gel materials,soda residue,modification,calcium (alumino) silicate hydrate,shear strength,freeze-thaw cycle,freeze-thaw mechanism

ReleaseDate:2018-03-20 15:26:55

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