Z E M C H 2 0 1 2 I n t e r n a t i o n a l C o n f e r e n c e
672
OPC Length variation specimen was demolded same as strength specimen at age of 1
day and the length variation graph measured up to the age of 28 days are as shown in
Figure 7. RC EAFRS powder showed similar shrinkage value similar to RSC up to the
early age of day 1, but relative shrinkage increases over the long-term age.
Figure 6: Compressive Strength of RC EAFRS Figure 7: Length Variation of RC EAFRS
3.6 Hydrate Analysis(XRD, SEM)
As for hydration process of regulated set cement(RSC), C
11
A
7
CaF
2
reacts with Ca(OH)
2
and CaSO
4
leached from C
3
S to create ettringite and develops early strength by
cohesive power between its needle-shaped crystalization. Ettringite generally occurs
immediately after it starts to react with water and Figure 8 is the XRD graph of 30
minutes of hydration of RSC and RC EAFRS powder and clearly shows ettringite in RSC.
However, C
11
A
7
CaF
2
of RC reducing slag powder(RC EAFRS powder) creates CAH gel
in reaction with water. In addition, β-C
2
S included in RC EAFRS powder creates Calcium
Sulfoaluminate(CSA) or CA hydrate of the hexagonal system, which are known to have
big surface area and adhesive power.
Figure 8 X-ray diffraction patterns of the Rapidly Cooled EAF Reducing Slag powder
Figure 9 shows the Scanning Electron Microscope(SEM) photo of 10, 30, 60 minutes
after hydration of RC EAFRS powder. As shown in the figure, independent CSA particles
generated right after hydration are gradually combined by adhesive power and create
hydrate of continuous board wrapping the surface of mineral particle in 1 hour after
hydration. Pore is charged by their adhesion, contributing to the initial strength(before
1day).
