HYDRATION OF TRICALCIUM GERMANATE

The hydration characteristics of tricalcium germanate were examined. K inetics of tricalcium germanate hydration, and hydration product morph ologies and compositions were determined at 5-degrees-C intervals betw een 5 and 70-degrees-C. Complete hydration was rapidly achieved. X-ray diffraction indicated that tricalcium germanate reacted completely wi thin 2 h at all the temperatures investigated. However, a constant val ue for an Arrhenius activation energy could not be determined. At hydr ation temperatures above 45-degrees-C a small heat peak, which precede d the main calorimetric peak, appeared in the calorimetric curves. Cal cium hydroxide was rarely observed by SEM for hydration at temperature s below 45-degrees-C. Dense regions of calcium hydroxide were readily observed for hydration above this temperature. In contrast to the hydr ation of tricalcium silicate, an induction period was not observed nor was an extended period of diffusionally controlled reaction. Calcium germanate hydrate was fibrous with the fibre thickness exhibiting a te mperature dependence. Hydration product compositions were determined b y thermal gravimetry. Expressing the composition of calcium germanate hydrate as (CaO)3-x GeO2 . nH2O, the value of 3 - x decreases from 1.6 8 to 1.59 with increasing temperature from 5-70-degrees-C. The values obtained for n varied inconsistently between 2.4 and 3.3. The unit cel l of the calcium germanate hydrate was determined to be monoclinic. Ce ll parameters were a = 1.851, b = 1.1 47, c = 0.531 nm and beta = 98.1 0-degrees.