Abstract
The effects of various additives on pH and rates of setting reactions of a commercial zinc phosphate cement system were examined. While the addition of various organic materials to the cement powderproduced no effect on the pH changes, addition of both calcium oxide and calcium hydroxide to the cement powder increased the neutralization rate of water in contact with the cement surface when compared with the unaltered cement. The addition of both magnesium oxide and magnesium hydroxide was effective in raising the initial pH of the cement. The addition of aluminum ion to the cement liquid retarded the setting reaction and delayed the neutralization of the cement when compared with cement liquid which contained no cation additives. Zinc ion showed a similar effect. There was a positive correlation between pH change and viscosity change for each cement during setting. X-ray diffraction and infrared spectroscopy suggest that the addition of zinc ion to the cement liquid induces the formation of hydrated zinc phosphate (Hopeite) during setting, while the addition of aluminum ion probably forms an amorphous phosphate without Hopeite.
