Compressive properties and microstructure of saline soil added fiber and lime under freezing-thawing cycles

Freezing in winter and thawing in spring lead to deterioration of the engineering property in the coastal saline soil in north China. In order to study the effect of the saline soil added lime (lime-soil) and saline soil added fiber and lime (fiber-lime-soil) on compressive capability, anti- freezing-thawing capability and microstructure, the freezing-thawing tests, unconfined compressive test, scanning electronic microscopy (SEM) test, nuclear magnetic resonance (NMR) test and mercury intrusion porosimetry (MIP) test are carried out, and the correlation between the compressive strength and microstructure characteristics, anti-freezing-thawing capability and its variation rules are systematically analyzed. The test results show that the compressive strength, pore volume and porosity of lime-soil and fiber-lime-soil under the freezing-thawing cycles are varied by four stages, that is, stage one (1−3 freezing-thawing cycles), stage two (4−7 freezing-thawing cycles), stage three (8−10 freezing-thawing cycles), stage four (11−15 freezing-thawing cycles). At the same freezing-thawing cycles, the failure strains of lime-soil and fiber-lime-soil increase with the increasing compactness, and the compressive strength and failure strain of fiber-lime-soil are greater than those of lime-soil, but the porosity is lower than that of lime-soil. The more the compactness is, the stronger the friction between fibers and particles, and the better the compressive properties. The interleaved fibers and randomly distributed fibers jointly limit the deformation of the soil and enhance the anti-freezing-thawing properties of the fiber-lime-soil. The results may provide the guidance in theory and technology for engineering utilization in saline soil areas in northern China.