The poor engineering properties of soils containing high amounts of clay minerals can be altered through chemical stabilization, resulting in a material suitable for geotechnical applications. The primary objective of this research was to study the time-dependent changes in the structure of lime stabilized montmorillonitic and lateritic clays using solid state nuclear magnetic resonance (SS-NMR) and Fourier transform infrared (FTIR) spectroscopy. The 29Si and 27Al MAS NMR spectra of montmorillonite dominated soils indicated that the reaction products of the attack on the tetrahedral sheets were mainly responsible for the formation of new composites that bound the soil particles together. Furthermore, the coating of iron (hydr)oxides on the surface of the laterite clay particles retarded the pozzolanic reactions. The presence of lime in the soil-stabilizer matrix was also confirmed by a new band observed in the FTIR spectra. From the geotechnical point of view, the lime treated bentonite showed the highest degree of improvement with an approximately 11-fold strength increase in comparison to the natural soil within 8-month curing periods.