Abstract It is not uncommon for Geotechnical Engineering works to be carried out under unfavorable conditions that compromise the earth-stability. In this context, the Paraguayan Region of Chaco is notably known owing to the presence of problematic soils that possess dispersive characteristics and/or present high amounts of soluble-sulfates content. Geomaterials of such nature affect mainly the road infrastructure earthworks due to, respectively, their promptness to erosive phenomena when in contact with water and swelling owing to the grown and hydration of expansive minerals such as ettringite and thaumasite, when treated with calcium-based materials. Therefore, present research presents a detailed characterization of a dispersive soil and a sulfate-rich dispersive soil, both collected in the Western Region of Paraguay. Physical, chemical and microstructure tests were carried out in order to verify and explain the deleterious behavior observed in both soils.