Experimental study on mechanical properties and microstructure of metakaolin based geopolymer stabilized silty clay

Geopolymer is an environmentally friendly green building material with fast hardening, high strength, low shrinkage, low cost, and low carbon dioxide emission. Based on the above characteristics of geopolymer, this study aims to explore the feasibility of taking geopolymer as a new choice for silty clay foundation treatment. In this study, unconfined compressive strength tests, scanning electron microscopy (SEM), and X-ray energy dispersive spectroscopy (EDS) experiments were carried out on silty clay stabilized by metakaolin based geopolymer (MKG). The influences of metakaolin content, modulus, and concentration of alkali activator on the mechanical properties of geopolymer stabilized soil were discussed. The mechanism of MKG improving the soil strength was also discussed from the microscopic point of view. The result showed that when the modulus of alkali activator is 1.3, the concentration is 40%, and the mixed mass of metakaolin is 1.2 times that of alkali activator, MKG stabilized soil showed higher unconfined compressive strength (UCS). Through comparative tests with untreated plain soil, lime stabilized soil and ordinary Portland cement stabilized soil, the strength performance and stabilizing effect of MKG stabilized soil were further studied. MKG has an obvious effect on improving the UCS of soil, and its mechanical indexes including UCS, Young's modulus, failure strain were also enhanced compared with samples stabilized with lime and ordinary Portland cement. SEM observation confirmed the formation of cementitious materials in the stabilized soil sample, the soil showed a more uniform and denser microstructure after treatment with MKG. Through EDS energy dispersion spectroscopy analysis, it is not easy to cause salt swelling damage with no large amount of calcium ions in the sample. This experimental study indicated that MKG can be an effective soil solidification agent for silty soil.