Behavioral evaluation on the engineering properties of lignin-stabilized loess: Reuse of renewable materials

Lignin as an eco-friendly material is being studied in the field of soil modification. To examine its feasibility and performance in solidifying loess, this study carried out a series of laboratory tests on physical, chemical, and mechanical properties of lignin-stabilized loess, including Atterberg limits, standard Proctor compaction, unconfined compressive strength, dynamic triaxial torsional shear, pH, conductivity, X-ray diffraction, and scanning electron microscope test, taken into account the effects of curing time and freeze–thaw cycles, analyzed the solidification mechanism. The results showed that the Atterberg limits, maximum dry density, and optimum moisture content were not affected by the lignin content. The strength of stabilized loess showed increased first and then decreased with the growth of lignin content, and the maximum strength was achieved at the lignin content of 1.5%, strength increased by nearly 60%. The strength of the test sample decreased significantly under freeze–thaw cycles, but after 6 cycles, the strength tended to stabilize. The pH value showed a declining trend with the growth of lignin content, while the conductivity showed an opposite trend. The Attberg limits, pH, and conductivity of the stabilized loess were hardly affected by freeze–thaw action. In addition, the results of X-ray diffraction indicated that there was no new mineral composition generated in the stabilized loess.