Strength characteristics and solidification mechanism of sulphate salty soil solidified with sodium silicate

Abstract

Chemical consolidation is one of the most effective methods for solving the engineering problems of saline soil, such as salt expansion, collapse and erosion. Based on the unconfined compressive strength test, X-ray diffraction, chemical analysis and scanning electronmicroscope, the solidification mechanism and strength characteristics of the sulphate saline soil solidified by lime, fly ash and sodium silicate are analyzed. The results show that when the lime content is less than 8%, the compressive strength and shear strength of lime-reinforced soil, fly ash and sodium silicate are higher than those of the sulphate saline soil solidified by lime and fly ash; the strengths of the former grow almost linearly with the concentration of sodium silicate. The alkali-activated action on fly ash caused by sodium silicate and adsorption between sodium silicate and saline soil generate mass gels, leading to an increase in contact area between framework grains, a reduction in intergranular pore, and a transformation from point-contact to surface-contact. The grains of saline soil bond each other into 3D framework via gels, resulting in an increase in the strength of saline soil. Meanwhile, the salt expansion behavior of saline soil is also restrained effectively due to the sharp reduction in the content of SO42-induced by complex physicochemical reactions as saline soil is solidified. © 2016, Academia Sinica. All right reserved.