Civil Engineering Reference
In-Depth Information
Figure 29.
Differential thermal behavior of C
4
AF-gypsum (w/s ratio 0.5 or 1.0) hydrated
for 2 days at 25 or 80°C.
Chen and Shi
[52]
compared by DTG the hydration reaction of the
ferrite phases C
4
AF and C
6
AF
2
in the presence of gypsum. In DTG curves
they detected tricalcium aluminate sulfate, gypsum, low sulfoaluminate,
and Fe(OH)
2
gel. The ettringite transformed to the low sulfate form after all
gypsum was exhausted. The process of C
6
AF
2
hydration was similar to that
of C
4
AF. The gel phase was found in greater amounts in C
6
AF
2
and some
Ca(OH)
2
was also generated. It was concluded that the rate of ettringite
formation from C
6
AF
2
was slower than that from C
4
AF. When calcium
hydroxide was also used with gypsum, the formation of ettringite was
retarded.
