Abstract: In order to understand the effect of the alkalinity of metakaolin base polymer binder on the improvement of clay，the effects of the concentration of alkali activator substance，the different concentra⁃ tion of metakaolin based polymer and curing time on the unconfined compressive strength of the sample， and whether the geopolymers react with substances in the clay were studied. The results show that，com⁃ pared with the original clay，the unconfined compressive strength increases with the increase of metakaolin content and the molarity of NaOH. The compressive strength of the sample with 8 mol/L NaOH concentra⁃ tion and 12% NaOH dosage was 4109 N after curing for 28 days，which was 112% higher than that of the original clay. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis showed that the geopolymer reacted with the clay to form cementing particles，which were covered by cementing com⁃ pounds. The effectiveness and stability of polymeric binder based on metakaolin were verified under normal temperature and strong alkali environment. The results can provide a basis for the application and popular⁃ ization of metakaolin base polymer in soil improvement engineering.

Key words: metakaolin, geopolymer, alkali excitation, surface structure, mechanical property