The formation process of aluminum hydroxide in calcium sulfoaluminate pastes
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ORIGINAL PAPER
The formation process of aluminum hydroxide in calcium sulfoaluminate pastes Fei Song1,2 · Yinong Lü2 · Honggang Qin3 · Yunfei Liu2 · Jian Xiao1 · Wenjuan Liu1 Received: 9 July 2020 / Accepted: 9 September 2020 © Institute of Chemistry, Slovak Academy of Sciences 2020
Abstract Aluminum hydroxide phase ( AH3) is one of the hydration products for calcium sulfoaluminate. In this paper, the microstructure and formation process of AH3 at different temperatures and water/solid ratios were investigated via scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results suggest that not only a high water/solid ratio but also a high temperature promoted the formation of AH3, and changed the microstructure of AH3. The AH3 with various morphologies, formed together with ettringite and monosulfate, were found and confirmed in the pastes. The filamentous and lamellar A H3 were observed in the early stages. Then, the A H3 often gathered and grew forming smooth or lamellar spherical A H3. At last, the spherical AH3 usually continued to aggregate, forming dense or lamellar agglomerated AH3 in the later stages. Keywords Calcium sulfoaluminate · Hydration · Aluminum hydroxide · Ettringite · Monosulfate
Introduction Calcium sulfoaluminate (C4A3Š), also known as Klein component or ye’elimite, is the main mineralogical phase of a promising low-CO2 alternative to ordinary Portland cement (OPC) and C 4A3Š-containing cements have received significant attention for their excellent performance (Li et al. 2020; Shen et al. 2018; Šiler et al. 2014; Staněk and Sulovský 2015). For example, calcium sulfoaluminate cement (CSA) manufactured by sintering mixtures of limestone, bauxite, and gypsum at a temperature of approximately 1250 °C has good performance of rapid hardening, high strength, low alkali, and so on (Quillin 2001; Sirtoli et al. 2019). At Cement nomenclature will be used, i.e., C = CaO, Š = SO3, Č = CO2, A = Al2O3, H = H2O. * Fei Song [email protected] 1
College of Materials Science and Engineering, Hunan Provincial Key Laboratory of Advanced Materials for New Energy Storage and Conversion, Hunan University of Science and Technology, Xiangtan 411100, China
2
College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009, China
3
China Railway No. 3 Engineering Group Co., Ltd, Taiyuan 030000, China
the same time, manufacturing CSA can fully utilize industrial by-products, such as fly ash, steelmaking slag, marble sludge, and the calcination temperature of clinker using wastes as raw materials can be reduced to 1200 °C (Adolfsson et al. 2007; Canbek et al. 2020; El-Alfi and Gado 2016). Note that the excellent characteristics of CSA mainly derive from the high active mineral C4A3Š (Hargis et al. 2013; Hu et al. 2017; Michel et al. 2011; Winnefeld and Barlag 2010). The crystal structure of C 4A3Š has been reported to be cubic, tetragonal, and orthorhombic at different conditions (Gastaldi et al. 2016; Hargis et al. 2014; Jansen e
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