Abstract:The properties of calcium phosphate cement consisting of α-tricalcium phosphate (α-TCP) and tetracalcium phosphate (TTCP) have been investigated by using a cement liquid that contained citric acid with concentration of 0.05mol/L or higher. The relationship between the setting time of the system cement and the concentration of citric acid solution shows concave type curve. When solution concentration was 0.2mol/L, the setting time was 8min, which was t he shortest. While the relationship between 24h compressive strength of the cement and the citric acid concentration shows convex type curve. When solution concentration was 0.2mol/L, the compressive strength was 39.0MPa, which was the highest. Afterwards, the microstructure of the hardening product w as observed by SEM, the effect of citric acid on the exothermic rate of hydrate reaction was studied by microcalorimeter, and the crushed specimens were subject ed to X-ray diffraction. The results verified that the low citric acid concentration can accelerate the hydrate reaction rate of the α-TCP/TTCP system. However, the high citric acid concentration inhibited hydroxyapatite formation an d retarded the rate of hydrate reaction of the α-TCP/TTCP cement.

Key words: α-TCP/TTCP cement; citric acid; setting time; compressive strength; HAP formation