Structure, microstructure and thermal stability characterizations of C3AH6 synthesized from different precursors through hydration

Abstract

In this paper, the influence of precursors (CA, C 7 A 3 Z, C 12 A 7 , C 6 SrA 3 Z, C 7 A 2 FZ and commercial calcium aluminate cement 'Gorkal 70') on the structure, microstructure and thermal stability characterizations of C 3 AH 6 through hydration was investigated. The materials were characterized by X-ray diffraction, differential thermal analysis-thermogravimetric analysis-evolved gas analysis and scanning electron microscopy combined with energy-dispersive spectroscopy 24 h and 72 h after starting the hydration process. Results of investigation confirmed the influence of precursor on shape and grain size of C 3 AH 6 . The CaO/Al 2 O 3 mass ratio of precursors before the hydration process affects the size of C 3 AH 6 crystals: the higher the CaO/Al 2 O 3 value, the larger the size of the crystals of C 3 AH 6 . Moreover, the presence of Sr and Fe affects the formation of stable C 3 AH 6 crystals.

Preparation of CaCO3/Al(OH)3 Composites via Heterogeneous Nucleation

“…In comparison with Figure 3 a, the particle morphology changed remarkably, and the spherical and ellipsoid structure disappeared, indicating that the vaterite-type precipitated calcium carbonate has been converted into other species. Combined with XRD analysis, as shown in Figure 1 h, the formed sheet may refer to AH 3 or C 4 AcH 11 , and the granular structure may refer to C 3 AH 6 , as reported by Li [ 26 ], Litwinek [ 19 ] and Shang [ 27 ]. Figure 4 b shows that the surface of calcite-type precipitated calcium carbonate composite is composed of lamellar, granular, and prismatic morphology, while the cubic crystalline structure morphology cannot be found.…”

“…The ground calcium carbonate composite sample with a particle size of less than 500 mesh showed new strong diffraction peaks at 17.28° and 18.50°, which can be ascribed to the C 3 AH 6 and Al(OH) 3 (AH 3 ) phases, respectively. In addition, only a weak peak was observed at 11.71°, which belongs to the (011) crystalline planes of the 3CaO·Al 2 O 3 ·CaCO 3 ·11H 2 O (C 4 AcH 11 ) phase [ 19 ] (JCPDS #87-0493).…”

Strontium Retention of Calcium Zirconium Aluminate Cement Paste Studied by NMR, XRD and SEM-EDS

“…The cement powders which were obtained by grinding the sintered pellets and necessary mass of water were mixed together in a glass beaker to obtain three homogeneous neat cement pastes. Each neat cement paste was then placed in a polyethylene bag and sealed until 14 d at 50 • C. According to Litwinek and Madej [5], the optimal synthesis temperature for C 3 AH 6 from different precursors through hydration is suggested to be 50 • C. Moreover, this period for curing cement pastes was accepted to attain the maximum degree of hydration, as concluded from the previous studies [13]. Moreover, as it was previously mentioned by Garcés et al [26] and Zhang et al [27], at temperatures as high as 60 • C, only the cubic phase and the gibbsite appear in the calcium aluminates-based cement pastes.…”

“…Calcium aluminate cements (CACs) [1][2][3] and other related cementitious systems [4][5][6][7] are believed to play an important role in a wide range of specialist are as from some construction areas and civil engineering, to refractory materials industry, due to their ability to gain strength rapidly in the initial days after casting and to withstand aggressive environments and high temperatures. The temperature-time weight ratio of water-to-cement (the w/c ratio) dependencies of the cement hydration processes have been widely investigated so far and are presented elsewhere in detail [8][9][10].…”

“…Because strontium is chemically closely related to calcium, it is easily introduced as a natural substitute for calcium in aluminate phases. Strontium has been shown to affect the hydration behavior of calcium zirconium aluminate cement [5,13]. Furthermore, strontium-containing cements attract the attention of materials scientists due to their higher refractory properties, increased resistance to thermal shock, increased resistance to chemical aggressive solutions and possible applications as special binders for shielding constructions in nuclear power plants [14].…”