Cementation of hazardous organic liquid wastes such as radioactive liquid scintillator is receiving increasing importance. Using clay as natural adsorbent to improve the incorporation process of these organic wastes into cement paste was performed. The waste form composed of water/cement at the ratio 0.3 with 3 % solid natural clay by the weight of cement and incorporating up to 15 % real spent organic liquid scintillator waste by the weight of cement-based paste was prepared. The temperature changes accompanying with the cementation process were followed. The nominated solidified cement–clay composite was also subjected to free falling test at different heights to evaluate its structural stability during unexpected transportation events or disposal site impacts. Scanning electron microscopy and X-ray investigations were used to evaluate the microstructure of the composite. The results revealed that the proposed cement–clay composite could be nominated structurally as a durable matrix for incorporating up to 15 % of liquid scintillator safely. .