Research on strength improvement and stabilization mechanism of organic polymer stabilizer for clay soil of subgrade

Soil stabilizer can improve the physical and chemical properties of clay and improve the bearing capacity of subgrade soil. A kind of liquid polymer soil stabilizer of vinyl acetate-ethylene was used in this paper. First of all, the effects of stabilizer content and curing time on the unconfined compressive strength (UCS) and the water stability were studied to clarify the strength evolution of stabilized soil. Furthermore, the pH test, Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), X-Ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR) were performed to study mineralogy, morphology, and chemistry of clay minerals and polymer stabilizer, as well as the potential interaction of the both. The results show that the stabilized soil has a quick strength growth before 14d that reaches about 89% of the final strength, then followed by a decreasing growth rate. Extending the curing time and increasing stabilizer content contribute to the dense agglomeration structure and homogenous skeleton structure. When immersed in the water, the strength has the largest reduction amplitude within the first day. The pore-filling effect, physicochemical bonds, and surface wrapping for clay particles are dominating roles of the polymer stabilizer. The formed fine colloidal particles could fill micro-pores distributed in the matrix. In addition, the polar functional group of carbonyl could create a strong electrostatic attraction and hydrogen bond with the clay minerals, further improving the adhesion, while there are no other new function groups generated. The polymers containing hydrophobic groups are recommended in consideration of water stability.