Portland cement has been widely used to stabilize hazardous and radioactive wastes. In spite of its many advantages as a solidification matrix, their mechanical strength and chemical durability (leach resistance) are relatively low. Modification of cement matrix using supercritical CO₂ (SCC) is proposed as a viable method to enhance these properties. In this study, as a pre-step to the SCC modification, cement matrices are fabricated with an addition of slaked lime and Na-bentonite and their characteristics are investigated.