Civil Engineering Reference
In-Depth Information
11% RH. Feldman and Ramachandran
[4]
have estimated that the bottled
hydrated C-S-H equilibrated to 11% RH (approached from 100% RH) has
a composition of 3.28CaO:2SiO
2
:3.92H
2
O. In another procedure, known as
d-drying, the sample is equilibrated with dry ice at -79°C. In this method,
some chemically bound water is lost from the interlayer. It may, however,
be used as an empirical method to measure the degree of hydration. The
water content of fully hydrated C
3
S is given as 20.4-22.0% and this
corresponds to a C-S-H composition 1.7 CaO•SiO
2
•1.3-1.5H
2
O.
The rate of hydration of C
3
S has been determined by following the
consumption of C
3
S, non-evaporable water or Ca (OH)
2
with time. In Fig.
1, the general form of curve relating the fraction of C
3
S consumed as a
function of time in a paste hydrated at a W/S ratio of 0.5 is given.
[5]
Various
stages of reaction could be related to the conduction calorimetric curves. At
120 days, more than 80% hydration has taken place. At one year presumably
all C
3
S has been consumed.
Figure 1.
Fraction of tricalcium silicate consumed as a function of time in a paste.
