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论文类型：期刊论文

发表时间：2018-08-20

发表刊物：CONSTRUCTION AND BUILDING MATERIALS

收录刊物：SCIE

卷号：180

页面范围：655-664

ISSN号：0950-0618

关键字：Aluminum hydroxide; Calcium sulfoaluminate cement; Alkali; Microstructure

摘要：The present paper discusses the microstructural evolution of aluminum hydroxide (AH(3)) formed during the hydration of calcium sulfoaluminate in neutral and alkaline solutions (0-M NaOH, 0.01-M NaOH, 0.1-M NaOH, 1-M NaOH, 5-M NaOH and 8-M NaOH). Rietveld method and field emission scanning electron microscopy measurements were used to observe the evolution of crystallite size and particle size distribution, respectively. Furthermore, various characterization methods were used to complement the microstructure of AH(3 )phase. The result of( 27)Al MAS-NMR spectroscopy indicated the absence of the amorphous AH(3 )phase in all hydrated pastes. The degree of crystallinity, with respect to the AH(3 )phase, improved with increasing alkali concentration. However, AH(3 )phase can also react with OH- ion and even disappear in high alkaline conditions. In low alkaline conditions (i.e., 0-M NaOH, 0.01-M NaOH, 0.1-M NaOH), the AH(3 ) phase had a nanocrystalline structure with an average crystallite size of about 8-9 nm and particle size distribution ranging from 110 nm to 210 nm. In high alkaline conditions (i.e., 5-M NaOH and 8-M NaOH), the AH(3 ) phase presented a well-crystalline nature. The average crystallite size increased up to about 30-40 nm and the particle size distribution was mostly 800-1400 nm (5-M NaOH) or 1000-1500 nm (8-M NaOH). (C) 2018 Elsevier Ltd. All rights reserved.