Abstract
In order to prepare a good radiation shielding concrete with a proper setting time and a high strength, the hydration properties of cement with boron gangue were investigated by the methods of XRD, isothermal microcalorimetry, TG/DSC, and FTIR. The results demonstrated that it was mainly related to the insoluble matter CaB2O4·4H2O and Ca(H2BO3)2·4H2O that boron gangue could severely inhibit the cement hydration. Boron gangue made a significant retardation on Portland cement hydration with the form of BO33− and BO45−, which caused an obvious retardation of C3A and C3S hydration with an insoluble coat and a low solubility of calcium ion in the solution. Therefore, it is important and necessary to take into consideration the chemistry of borates in aqueous and the kind of cement-based or cementitious materials used for radiation shielding concrete with boron or boron compounds, especially for the materials with a high content of C3A and C3S.
Highlights
Experimental ProgramC3A was prepared by chemosynthesis of a well-blended mixture of analytical grade CaCO3 and Al2O3 at 1380°C. e synthesised product was analysed by X-ray diffraction (XRD) and cubic Ca3Al2O6 (C3A) phase was detected (Figure 1) with a specific surface area of 350 m2/kg which was determined by Blaine’s method
In order to prepare a good radiation shielding concrete with a proper setting time and a high strength, the hydration properties of cement with boron gangue were investigated by the methods of X-ray diffraction (XRD), isothermal microcalorimetry, TG/DSC, and Fourier transformation infrared spectrometer (FTIR). e results demonstrated that it was mainly related to the insoluble matter CaB2O4·4H2O and Ca(H2BO3)2·4H2O that boron gangue could severely inhibit the cement hydration
Boron gangue made a significant retardation on Portland cement hydration with the form of BO33− and BO45−, which caused an obvious retardation of C3A and C3S hydration with an insoluble coat and a low solubility of calcium ion in the solution. erefore, it is important and necessary to take into consideration the chemistry of borates in aqueous and the kind of cement-based or cementitious materials used for radiation shielding concrete with boron or boron compounds, especially for the materials with a high content of C3A and C3S
Summary
C3A was prepared by chemosynthesis of a well-blended mixture of analytical grade CaCO3 and Al2O3 at 1380°C. e synthesised product was analysed by XRD and cubic Ca3Al2O6 (C3A) phase was detected (Figure 1) with a specific surface area of 350 m2/kg which was determined by Blaine’s method. C3S was synthesised by chemosynthesis of a well-blended mixture of analytical grade CaCO3 and SiO2 at 1500°C. e synthesised product was monoclinic Ca3SiO5 (C3S) phase (Figure 1) with a specific surface area of 410 m2/kg, and free lime content is less than 0.10 wt%. On the basis of the content of C3A and C3S in clinker or cement (Table 1), in order to avoid possible heterogeneities in the mixture and decrease the concentration gradients at the interface between solid and aqueous phase, another four paste samples were prepared with a high w/c (water-cementitious ratio) (Table 3). In order to study the situation of hydrated products changing with temperature, isothermal microcalorimetry (C80, Setaram company, France) of hydration system is performed under a nitrogen atmosphere
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