Investigation of hydration phases in the system CaO-SiO₂-P₂O₅-2o

Hydration reactions and their rates have been studied qualitatively in CaO^- and P₂0₅-rich compositional regions of the system Ca0-Si0₂-P₂0₅-H₂0. Using aqueous solutions of Ca(N0₃) ₂ • 4H₂0, Ludox, and H₃P0₄ as starting materials, amorphous powders made by the sol-gel process were reacted with water. Some “curing” reactions were carried out at several temperatures: Room temperature, 90 °C, and under hydrothermal conditions. Some glasses in the phosphate-rich region of the system were also made and hydrated. The hydration products are OH-Ap [OH-Ap = Ca₁₀(PO₄)₆.(OH)₂], Ca(OH)₂[CH = Ca(OH)₂],C-S-H crystalline, C-S-P-H (C = CaO,S = Si0₂,P = P₂0₅,H = H₂0) crystalline, C-S-H gel, C-S-P-H gel, Ca (H₂P0₄) ₂) H₂0, and CaHP0₄. All phases have been identified and characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray analysis (EDAX). The reactivities of the precursor materials and the compositional-structural nature of the hydration products formed are discussed. Some new compositions for “cementlike behavior” have been discovered.