水泥改良冻土过程水分转化规律及对强度的影响

为保证多年冻土区地基的稳定性及解决多年冻土区土方材料短缺的问题,分别使用硫铝酸盐水泥(SAC)和普通硅酸盐水泥(OPC)对冻土进行改良。通过无侧限抗压强度试验得到两种水泥在不同掺量及不同养护龄期下的强度特征,同时,使用离心机法及冻干法对水泥改良冻土过程中的自由水、矿物水及结合水的变化进行测定,揭示水泥改良冻土过程中的水分转化规律,并建立矿物水、结合水量与水泥改良冻土强度的内在联系。结果表明:硫铝酸盐水泥改良冻土的强度明显高于普通硅酸盐水泥,并且具有显著的早强特性。硫铝酸盐水泥改良冻土在养护初期水分转化速率较普通硅酸盐水泥快,但矿物水及结合水的转化量少。硫铝酸盐水泥改良冻土中的矿物水和结合水对强度的贡献更为突出。硫铝酸盐水泥更适合用于冻土的改良。

Water transformation law of cement improved frozen soil and its effect on strength

Sulphoaluminate cement and ordinary Portland cement were used to improve the frozen soil in order to ensure the stability of foundation and solve the problem of shortage of earthwork materials in permafrost area. In this study, the strength characteristics of the two types of cement were obtained by unconfined compressive strength tests at different dosages and different curing ages. The variation of free water, bound water, and constitution water were measured with the methods of centrifuge and freeze dryer in the process of cement improving frozen soil. The law of water transformation in the process of improving frozen soil was explored, and the relationship between constitution water, bound water, and the strength of improved frozen soil were established. Results show that the strength of the improved frozen soil treated with sulphoaluminate cement was obviously higher than that treated with ordinary Portland cement. Sulphoaluminate cement presented remarkable early strength characteristics. The water transformation rate of sulphoaluminate cement was faster than that of ordinary Portland cement in the early stage of curing, but the transformation amount of constitution water and bound water was low. The contribution of constitution water and bound water to the strength was more significant in sulphoaluminate cement improved frozen soil than in ordinary Portland cement. Sulphoaluminate cement is more suitable to improve frozen soil.