Formation and strengthening mechanisms of xonotlite in C3S-silica and C2S-silica powder systems under high temperature and pressure. (July 2022)

• Record Type: Journal Article
• Authors: Wei, Tingcong; Wei, Fengqi; Zhou, Jinghong; Wu, Zhiqiang; Zhang, Chunmei; Zhuang, Jia; Cheng, Xiaowei
• Is Part Of: Cement and concrete research. Volume 157(2022)
• Publication Date: 2022-07
• Subjects: High temperature -- Tricalcium silicate -- Dicalcium silicate -- Silica powder -- Xonotlite -- Strengthening mechanism; Cement -- Periodicals; Cement -- Research -- Periodicals; Concrete -- Periodicals; Concrete -- Research -- Periodicals; Ciment -- Périodiques; Béton -- Périodiques; Cement; Concrete; Periodicals; 620.135
• DOI: 10.1016/j.cemconres.2022.106812
• Languages: English
• ISSNs: 0008-8846

Abstract

Abstract: As oil and gas exploration advances into more complex underground formations, oil-well cement, used to support bore casings, is at risk of mechanical failure. To clarify the strengthening mechanisms of silica powder, the hydration characteristics of C3 S-silica and C2 S-silica powder systems were studied at high temperature (230 °C) and pressure (20.7 MPa). The results show that microstructural coarsening is the primary reason for the poor mechanical properties of the cementitious materials. The formation of xonotlite included two sources: the crystallisation reaction of silica powder with C-S-H and the pozzolanic reaction of silica powder with calcium hydroxide. The CaO layer in C-S-H and calcium hydroxide provided a 'Ca' source for the formation of xonotlite. Q 2 and Q 3 Si units with a high polymerisation degree improve the high-temperature stability of xonotlite, while the dense structure formed by xonotlite improves the mechanical properties. For designing high-performance high-temperature resistant cement-based materials, xonotlite should preferably be generated by selecting crystalline silica powder.