Interface characteristics of oil-well cement and rock asphalt coated by dicalcium silicate

Abstract

Rock asphalt can be used feasibly to toughen oil-well cements. However, the interface between non-hydrophilic rock asphalt and cement is poor, which reduces the overall mechanical properties of the composites. Therefore, in this study, the sol–gel method was used to synthesise dicalcium silicate (C₂S), which was applied as a coating on the surface of rock asphalt to improve its interfacial bonding with cement. Our analysis indicated that the formed C₂S consisted of β crystals with an average particle size of 13.622 µm. Infrared testing showed the presence of O–Si–O, Si–OH, and Si–O bonds in C₂S-coated rock asphalt. Scanning electron microscopy and energy-dispersive X-ray analysis indicated that C₂S has been grafted on the surface of rock asphalt. Compared to untreated rock asphalt, the surface free energy of C₂S-coated rock asphalt increased from 12.71 to 35.83 mJ/m² while the interfacial binding energy with cement increased from 45.61 (untreated rock asphalt) to 84.76 (C₂S-coated rock asphalt) mJ/m². In addition, mechanical testing showed that the tensile strength and toughness of C₂S-coated rock asphalt-containing cement composites were very high. This is because C₂S-coated rock asphalt formed an excellent transition zone at the interface with the cement matrix, resulting in a strong and durable interface.

Keywords:

• Rock asphalt
• dicalcium silicate
• oil-well cement
• interface characteristics
• mechanical properties

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No potential conflict of interest was reported by the author(s).

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

The authors are grateful for the support provided by the National Key R&D Program of China (2016YFB0303600), the State Key Laboratory of Safety and Health for Metal Mines (2019-JSKSSYS-007), the key laboratory of the development and utilization of advanced materials for natural gas (X151519KCL20), and the financial support by the National Natural Science Foundation of China (51874254). The authors also would like to thank Advanced Cementing Materials Research Center of SWPU for the kind assistance in laboratory testing.