Page 468 - Handbook of Thermal Analysis of Construction Materials

Section 6.0 - Magnesia-Phosphate Cements 443

The heat evolved (over 24 hrs) for calcium pyrophosphate-modi-
fied cements is shown in the calorimetric curves in Fig. 31. Phosphate
additions of 10, 25, and 40% were used. The modified cements have only
a minor effect on the rate of heat evolution. Progressive additions of
2CaO•P O reduce the total heat evolved per unit mass of sample.
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The hydration products formed in the systems described above
were x-ray amorphous. Hydrothermal treatment of the calcium phosphate-
modified OPC resulted in the formation of crystalline hydroxyapatite.

Figure 31. Calorimetric curves showing (a) rates of heat evolution and (b) total heat
evolved as a function of time for OPC and OPC modified by 2CaO•P O during the first
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24 hours of hydration. A: OPC; B: 10% 2CaO•P O ; C: 25% CaO•P O ; D: 40%
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2CaO•P O . [27]
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