This paper deals with the SEM (Scanning electron microscope) analysis of improved soil. A natural dredged material from the Antwerp harbor was mixed with different binders (e.g. CEM I, CEM III). The soil and binders were mixed by means of the SSI (Soft Soil Improvement) technique in the field as well as with a dough mixer in the laboratory. An extensive SEM study was made on improved samples and natural soil to explain the strength behavior, looking at the microstructure of specimens.