Civil Engineering Reference
In-Depth Information
Thermal analysis data on the hydration of dicalcium silicate are
sparse because it is time consuming to follow the reaction of this phase
which is very slow. The characteristic products obtained during its hydra-
tion are not much different from those formed in C
3
S hydration. Also, the
major strength development that occurs in cement in the first 28 days (a
period of practical significance) is mainly due to the tricalcium silicate
phase. TG, DTG, and DTA investigations of C
2
S were carried out by
Tamas.
[40]
The sensitivity of the instrument had to be increased substan-
tially to detect the peaks due to the decomposition of calcium hydroxide and
calcium carbonate, especially at earlier times. In Fig. 21, the DTA, DTG,
and TG curves of C
2
S hydrated for 21 days and 200 days are given. A
comparison of these peaks with those obtained from C
3
S pastes shows
substantial differences in the intensity value of the peaks. The 200 day C
2
S
sample shows a weight loss of 4%, whereas C
3
S hydrated for 21 days
indicates a loss of 13%.
Figure 21.
Thermograms of C
2
S hydrated for 21 days and 200 days.
