Swelling soils in Egypt are found in several areas such as new Cairo, Madinat-Nasr, Alshrouk city, Assuit, New vally, Aswan and Edfu … etc. This paper discusses the physico-chemical properties and engineering behavior of expansive clays founded in Egyptian desert surrounding Cairo city. Five expansive soil samples were collected at the foundation levels of five different sites in new-built cities surrounding Cairo. Laboratory tests were performed on these soil samples to investigate physical properties of the various samples. Also, soil particle structure and clay mineralogy were investigated using Scanning Electron Microscope and X-Ray Diffraction. The obtained results show that clay mineral, its percentage, chemical composition and consistency limits affecting the swelling behavior. Also, the effect of replacement layer thickness on swelling reduction ratio is studied. The results proved that the efficiency of replacement layers in reducing the swell of expansive soil. Then, Data fit software is used to correlate the experimental results.