Page 395 - Handbook of Thermal Analysis of Construction Materials

Section 5.0 - Portland Cement-Calcium Aluminate Cement 373

Figure 6. Plots of matrix impedance vs hydration time for OPC-H-HAC pastes. The
numbers 1–3 correspond to those pastes containing 80, 50, and 20% of H-HAC
respectively, w/c = 0.50. [41]

5.4 Early Strength Development

Compressive strength results for three pastes (OPC/CAC ratios:
92.5/7.5; 80/20; 20/80) prepared at w/c ratio = 0.40 are presented in Table
1. [43] The early strength development of the 92.5/7.5 and 20/80 pastes is
very similar to that for pure OPC and CAC pastes. The 80/20 paste develops
strength earlier than the other two pastes, and it appears to have unique
strength development behavior.
Many factors affect the strength development of OPC/CAC sys-
tems. In the OPC/CAC binary cement pastes, ettringite can form in the first
few minutes of the hydration mainly through the following reactions:

Eq. (12) CA + 3CSH + 2C + 26H ⇒ C AS H 32
6
3
2
Eq. (13) C A + 3CSH + 26H ⇒ C AS H 32
3
3
2
6