X-ray investigations of solid solutions of monocalcium aluminate and monostrontium aluminate important phases in cement and phosphorescence materials

Abstract

Calcium monoaluminate is the main phase in calcium aluminate cements and participates in the hydration, forming calcium aluminate hydrates. The amount of incorporation of foreign ions influences the hydration behaviour. Strontium aluminate is an important phase in producing phosphorescent materials when doped with rare-earth elements (REE) such as Eu, Dy, and La. These monoaluminates occur in different forms. Monocalcium aluminate forms a monoclinic and an orthorhombic modification, whereas monostrontium aluminate forms a monoclinic low-temperature and a hexagonal high-temperature form. Monoclinic calcium monoaluminate and monoclinic strontium aluminate form a partial solid-solution series. The hydration behaviour of different solid solutions was also investigated using calorimetry. The newly formed strontium aluminate hydrates could be identified while similar strontium aluminate hydrates are formed. Solid solutions of strontium- and calcium-aluminate hydrates will be investigated.

Experimental evaluation on mechanical and thermal insulation properties of shotcrete under constant‐variable temperature

“…So, the compressive strength and splitting strength of OPSC decrease at 80°C. In addition, the calcium aluminate monocarbonate (Mc) phase is detected in OPSC at 60°C, which indicates that this temperature stimulates the reaction of CaCO 3 and C‐A‐H, and Mc is conducive to the strength development of shotcrete 63 …”

“…So, the compressive strength and splitting strength of OPSC decrease at 80 C. In addition, the calcium aluminate monocarbonate (Mc) phase is detected in OPSC at 60 C, which indicates that this temperature stimulates the reaction of CaCO 3 and C-A-H, and Mc is conducive to the strength development of shotcrete. 63 Figure 15 is the XRD pattern of PUSC. We observe that the phase of PUSC does not appear the phenomenon of low angle deviation of the diffraction peak in OPSC at 80 C. This is because the polyurethane in PUSC prevents a large amount of water from evaporating and ensures the water required for cement hydration at 80 C, so that the crystal structure does not change.…”

Interaction of layered double hydroxide phases with chloride ions

“…The two main chloride-containing AFm phases are Friedel's salt and Kuzel's salt. However, it is important to note that the composition of Friedel's salt is not fixed stoichiometrically as there exists a solid solution (Fsss) between Fs and monocarbonate, hemicarbonate or hydroxy AFm [42,[63][64][65][66][67][68][69]. For Kuzel's salt only limited solid solutions with either monosulphate or Friedel's salt have been reported [63,66].…”

“…However, it is important to note that the composition of Friedel's salt is not fixed stoichiometrically as there exists a solid solution (Fsss) between Fs and monocarbonate, hemicarbonate or hydroxy AFm [42,[63][64][65][66][67][68][69]. For Kuzel's salt only limited solid solutions with either monosulphate or Friedel's salt have been reported [63,66]. In addition, Kuzel's salt has been observed to be unstable in the presence of even small amounts of carbonate [63].…”

“…It is known, that sulphate ions in the interlayer of monosulphate can be replaced with chloride ions [63,83]. However, compared to monocarbonate, no solid solution exists between monosulphate and Friedel's salt [63,66]. Instead of a complete solid solution, a distinct phase, Kuzel's salt, can form at lower Cl concentrations [63,83].…”