Civil Engineering Reference
In-Depth Information
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
2
O
5
reduce the total heat evolved per unit mass of sample.
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
2
O
5
during the first
24 hours of hydration.
A:
OPC;
B:
10% 2CaO•P
2
O
5
;
C:
25% CaO•P
2
O
5
;
D:
40%
2CaO•P
2
O
5
.
[27]
