粉煤灰改性碱渣土的胶结特性与冻融机制

1)河北工业大学土木与交通学院,天津 300401; 2)河北省土木工程技术研究中心,天津 300401; 3)河北省水文工程地质勘查院,河北石家庄 050021

无机凝胶材料; 碱渣; 改性; 水化硅(铝)酸钙; 抗剪强度; 冻融循环; 冻融机制

Cementation characteristics and freeze-thaw mechanism of fly ash-modified soda residue soils
ZHAO Xianhui1, LIU Chunyuan1,2, ZHU Qin3, LIU Youcai3, MA Wang3, ZHU Nan1, LI Yanpeng1, and HU Lei1

ZHAO Xianhui1, LIU Chunyuan1,2, ZHU Qin3, LIU Youcai3, MA Wang3, ZHU Nan1, LI Yanpeng1, and HU Lei11)School of Civil Engineering and Transportation, Hebei University of Technology, Tianjin 300401, P.R.China2)Civil Engineering Technology Research Center of Hebei Province, Tianjin 300401, P.R.China3)Hydrological Engineering Geology Survey Institute of Hebei Province, Shijiazhuang 050021, Hebei Province, P.R.China

inorganic gel materials; soda residue; modification; calcium(alumino)silicate hydrate; shear strength; freeze-thaw cycle; freeze-thaw mechanism

DOI: 10.3724/SP.J.1249.2018.01048

备注

为促进碱渣和粉煤灰的综合利用,将两种材料合成粉煤灰改性碱渣土用于回填工程.通过界限含水率、击实、三轴和冻融循环试验,采用傅里叶变换红外光谱、扫描电镜-能谱和X射线衍射测试手段,研究改性碱渣土的胶结特性和冻融机制. 结果表明,改性碱渣土的最优含水率随着粉煤灰掺量增大呈先减后增趋势,在粉煤灰质量分数为50%时出现最小值. 以水化硅酸钙为主的产物凝胶使得改性碱渣土28 d抗剪强度在粉煤灰质量分数为50%时达到最大值. 养护龄期对改性碱渣土冻融机制影响显著. 冻融循环过程中,改性碱渣土在负温下水化硅(铝)酸钙(C-(A)-S-H)冻结,正温下C-(A)-S-H凝胶恢复胶结性; 水分向冻结边缘迁移,试样表面反复出现冰结而使得微裂缝向内部逐渐扩展,直到土样发生膨胀,抗剪强度降低; 同时在正负温交替作用下有微量CaSO4和CaSO4·0.5H2O晶体析出.

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.

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