The effects of BaSO4 loading on OPC cementing system for encapsulation of BaSO4 scale from oil and gas industry

Highlights: • Fine BaSO4 powder can promote the formation of CaCO3 in the wasteform. • w/c = 0.53 is better than w/s = 0.53 to maintain the low porosity and low carbonation. • Water has little impact on the formation of CaCO3 when coarse BaSO4 was introduced. • It is possible to load 60 wt% of BaSO4 with a sufficient integrity of wasteform. -- Abstract: The BaSO4 scales obtained from piping decontamination from oil and gas industries are most often classified as low level radioactive waste. These wastes could be immobilised by stable cement matrix to provide higher safety of handling, transportation, storage and disposal. However, the information available for the effects of the basic formulation such as waste loading on the fundamental properties is still limited. The present study investigated the effect of BaSO4 loading and water content on the properties of OPC–BaSO4 systems containing fine BaSO4 powder and coarse granules. The BaSO4 with different particle size had a marked effect on the compressive strength due to their different effects on hydration products formed. Introduction of fine BaSO4 powder resulted in an increased formation of CaCO3 in the system, which significantly contributed to the compressive strength of the products. Amount of water was important to control the CaCO3 formation, and water to cement ratio of 0.53 was found to be a good level to maintain a low porosity of the products both for fine BaSO4 powder and coarse BaSO4 granule. BaSO4 loading of up to 60 wt% has been achieved satisfying the minimum compressive strength of 5 MPa required for the radioactive wasteforms