氯氧镁水泥基流态固化土的改性与性能研究

Research on Modification and Properties of Magnesium Oxychloride Cement-based Fluid Solidified Soil

采用3种磷酸盐和2种聚合物乳液改性矿渣-氯氧镁水泥基固化土,探讨其工作性、力学性能、耐水性能和耐久性能等,应用Zeta电位和SEM测试分析其内部微观结构及形成机理。结果表明:除磷酸二氢钾使固化土流动度略有增大外,使用其他磷酸盐及聚合物乳液的改性固化土的流动度降低;掺磷酸二氢铵、聚丙烯酸酯乳液改性后的固化土的抗压强度较高,分别为5.13 MPa和4.04 MPa,远远高于高速公路及一级公路路基0.8 MPa的要求,其软化系数分别为0.98和0.95,超过耐水材料0.85的要求;在干湿循环试验后,改性固化土的质量和强度损失率显著降低。通过进一步机理研究发现,磷酸盐、聚合物乳液改性提高了土颗粒表面的负电位值,其中,磷酸根形成复合磷酸镁,抑制5相晶体水解,并与5相、3相及M-S-H凝胶等相互粘结形成了更加紧密的结构,聚合物在固化土孔隙界面形成保护膜,阻止了水的渗透,提高了固化土的强度。

This paper uses three kinds of phosphates and two kinds of polymer lotion to modify slag magnesium oxychloride cement-based solidified soil,and discusses its workability,mechanical properties,water resistance,and dry wet cycle resistance.Zeta potential and SEM tests analyzes its internal microstructure and formation mechanism.The results show that the fluidity of solidified soil modified with other phosphate and polymer lotion decreased,except that potassium dihydrogen phosphate slightly increased the fluidity of solidified soil;the compressive strength of the solidified soil modified with ammonium dihydrogen phosphate and polyacrylate lotion is higher,5.13 MPa and 4.04 MPa respectively,which is far higher than the requirement of 0.8 MPa for the subgrade of expressway and first-class highway,and its softening coefficient is 0.98 and 0.95 respectively,which exceeds the requirement of 0.85 for water resistant materials;the wet dry cycle test shows that the quality and strength loss rate of modified solidified soil are significantly reduced.Further mechanism research finds that the phosphate and polymer lotion modification improved the negative potential value of the soil particle surface.Among them,the phosphate radical formed composite magnesium phosphate inhibited the hydrolysis of 5-phase crystals and bonded with 5-phase,3-phase,and M-S-H gel to form a more compact structure.The polymer formed a protective film at the pore interface of the solidified soil,prevented the penetration of water,and improved the strength of the solidified soil.