Civil Engineering Reference
In-Depth Information
Triple DTA peaks have been observed in the region 270-340°C
with Secar 71 hydrated at 40°C and 50°C (and other Secar systems).
Thermograms are shown in Fig. 5. The peak at the lower temperature
(290-300°C) can be attributed to AH
3
, and that at 311-325°C to C
3
AH
6
. An
extra phase (attributed to the third peak) was not detected by XRD
suggesting that this phase was amorphous or poorly crystalline. There is
doubt, however, with this explanation given that the additional peak occurs
at a higher temperature than that observed for crystalline AH
3
, contrary to
expectation.
Typical DSC, TG, and DTG curves for high alumina cement
(HAC) pastes are provided by Brown and Cassel
[3]
in Figs. 6 and 7. They
illustrate that the techniques are complementary, as discussed previously.
Figure 5.
DTA traces of Secar 71 hydrated at 50°C showing a triple peak. XRD data is also
included.
[1]
