Stabilization using lime and cement is a widespread technique that provides civil engineering applications for soils with poor geotechnical performance. This article describes the effects of a combined lime+cement treatment on both the characteristics and properties of a plastic silt. A multi-scale approach was implemented and themechanical, microstructural and physicochemical changeswere investigated. To carry out these tasks, unconfined compressive strength measurements were conducted. The modifications caused by this treatment on the microstructure could be characterized by means of scanning electron microscope (SEM) observations of the soil composition, through element distribution maps and mercury intrusion porosimetry (MIP) analyses. The physicochemical evolution has beenmonitored by X-ray diffraction (XRD) analyses. Within the silt, clay particles surround the coarsest particles in order to formmillimeter-sized agglomerates, aroundwhich binders are deposited. During the curing period, the formation of C-(A)-S-H becomes readily apparent. These phases are detected in the form of a gel that provides continuity throughout the material; as such, the material displays a “honeycomb” type of microstructure. The mechanical properties of the treated soil are indeed affected by this microstructural organization. The post-treatment improvement in mechanical performance therefore proves to be significant.