Page 393 - Handbook of Thermal Analysis of Construction Materials

Section 5.0 - Portland Cement-Calcium Aluminate Cement 371

iii) Rapid hydration of CAC leading to a very dense matrix.
This stage corresponds to the second large increase of
impedance value.

iv) Matrix densification and decrease of impedance after the
second maximum.
The latter stage involves various reactions such as:

Eq. (8) 2CAH → C AH + AH + 9H;
10 2 8 3
3C AH → 2C AH + AH + 9H
2
8
3
3
6
– –
Eq. (9) 2C A + C AS H + 4H → 3C ASH 12
32
6
3
4
3
Eq. (10) C S + 2H → C-S-H + CH
2
Eq. (11) C S + 3H → C-S-H + 2CH
3

Figure 5. Plots of matrix impedance vs hydration time for OPC, HAC, and OPC-HAC
pastes. The numbers 1–6 correspond to those pastes containing 100, 80, 50, 33, 20, and 0%
HAC respectively. [41]