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

摘要

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 beta crystals with an average particle size of 13.622 mu m. 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/m(2)while the interfacial binding energy with cement increased from 45.61 (untreated rock asphalt) to 84.76 (C2S-coated rock asphalt) mJ/m(2). 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.