Civil Engineering Reference
In-Depth Information
Conduction calorimetry curves are presented in Fig. 18 for
C
11
A
7
•CaF
2
containing Ca(OH)
2
, CaSO
4
, CaSO
4
•2H
2
O, and CaSO
4
•½H
2
O
respectively.
The heat of evolution curve in the initial stage of hydration (of
C
11
A
7
•CaF
2
alone) typically consists of three peaks. The first large peak
appears immediately and is due to vigorous hydration of C
11
A
7
•CaF
2
forming several kinds of calcium aluminate hydrate. The second and third
peaks usually appear within one hour and one day respectively after mixing
with water. The second peak corresponds to the “overlapped” formation of
hexagonal calcium aluminate hydrate, e.g., C
2
AH
8
, C
4
AH
13
, and cubic
C
3
AH
6
as they are generally observed in the hydration of C
3
A, C
12
A
7
, and
CA. The third peak is due to the conversion of hexagonal calcium aluminate
hydrate to cubic C
3
AH
6
and the continued hydration of the remaining
C
11
A
7
•CaF
2
.
Figure 18.
Heat evolution curves of C
11
A
7
•CaF
2
pastes with Ca(OH)
2
and with calcium
sulfates (w/s = 0.60, 20°C).
[14]
