Civil Engineering Reference
In-Depth Information
Thermo-analytical techniques are applied widely to monitor the
reactions occurring in the raw clay materials and also to follow the
pozzolanic effects of metakaolinite when combined with lime or cement.
Not much work has been carried out on studies related to the
effect of MK on the hydration of individual cement compounds. The effect
of 30-90% MK addition to C
3
S and C
3
A hydration has been examined.
[61]
At a curing period of 28 days, the DTA curves indicate that as the C
3
S:MK
ratio decreases from 2.4 to 0.6, the peak due to CH (C) is decreased (Fig.
25). The main products were found to be C-S-H (A) and stratlingite
(B)(C
2
ASH
8
). At 90 days, C
3
AH
6
is also formed. These results show that
CH formed during the hydration is consumed by MK. It is also evident from
the figure that the amount of C-S-H formed is larger in the C
3
S:K mixtures
compared to that in pure C
3
S. The accelerating effect of MK on C
3
S
hydration is also confirmed by conduction calorimetric studies. The hydra-
tion of C
3
A is not influenced by MK.
[61]
Figure 25.
DTA of C
3
S pastes containing different proportions of metakaolinite. 1. C
3
S;
2. C
3
S:MK = 2.4; 3. C
3
S:MK = 1.4; 4. C
3
S:MK = 0.9; 5. C
3
S:MK = 0.6.
