Civil Engineering Reference
In-Depth Information
Triethanolamine influences the hydration of the C
3
S phase. The
effect of 0.5% TEA on the hydration of C
3
S is illustrated by DTA curves in
Fig. 12.
[17]
Figure 12a refers to the DTA behavior of C
3
S hydrated at a
w/s ratio of 0.5 from 5 minutes to 28 days. A small endothermal effect at
about 480-500°C appearing at 1 hour and increasing subsequently at later
ages is due to Ca(OH)
2
dehydration. In the thermograms of C
3
S, hydrated
in the presence of triethanolamine (Fig. 12b), a very small endothermal
effect representing the formation of Ca(OH)
2
appears only after 10 hours.
The curves indicate that TEA initially retards the rate of hydration of the
silicate. The sharp exothermal effect appearing at 6 hours is attributed to the
complex of TEA formed on the surface of the hydrating C
3
S. This complex
may be responsible for the retardation effect. TG results are in conformity
with those of DTA.
(a)
(b)
Figure 12.
Thermograms of C
3
S hydrated to different periods:
(a)
C
3
S + 0% TEA;
(b)
C
3
S
+ 0.5% TEA.
