A S t u d y o n t h e H y d r a t i o n C h a r a c t e r I s t I c s
649
3.4 Length Variation
Fig. 6 shows the length change for each binder type. The length change specimen, the
regulated setting cement and the EAFRS binder were measured after the remolding in
the initial 3-hour, and OPC was measured from 1-day of material age. The binder with
the single use of EAFRS had the longest length change that it showed a very high
contraction volume compared to OPC and regulated setting cement. However, in the
event of gypsum mixing binder, it showed the lower length change than OPC and, as the
mixture volume increased, the length change was lowered, and for the case of mixing for
40%, the volume was rather increased. In the event of single use of the EAFRS, the
CAH gel that was generated by the initial drastic reaction and calcium silicate alluminate
hydration material was generated around the non-hydration particle to cut off the water
penetration not to progress the hydration any longer to cause the volume reduction from
the CAH hydration material combination. On the other hand, in the event of mixing in the
gypsum, C
11
A
7
·
CaF
2
reacted with the gypsum to secure the volume stability following the
contraction compensation effect by the expansion of the ettringite generation.
Fig. 6 Length variation of binders
3.5 Hydrate Analysis (XRD, SEM)
Fig. 7 is the measurement of XRD for the binder mixing in of 30% gypsum and EAFRS
following the hydration time. In the event of using the EAFRS alone, C
12
A
7
and β-C
2
S
that did not hydrated after one day of hydration and the CAH hydration material was
measured, and in the event of the binder with 30% mixture of the gypsum, the initial
period of hydration had the ettringite generation in 1 hour of hydration. And, on the 1-day
of hydration, a number of ettringite was measured.
Fig. 8 was filmed by using the scanning electronic microscope for the hydration condition
that mixed 30% of the gypsum on the EAFRS specimen and 10 minutes, 1hours and 1
day of the binder. The EAFRS seemed to contribute to the initial strength by formulating
the hydration material membrane of continued plate shape on the non-hydration particle
surface only in one hour of hydration by having the CAH hydration material generated in
the first 10 minutes to make gradual combining. However, it was considered as the main
cause to interfere long-term strength and durability by making the hydration reaction
difficult by blocking off the continuous moisture penetration by wrapping around the non-
hydration particle surface.
In the event that the gypsum was mixed, the ettringite was confirmed on the short fiber in
early hydration period, and as the hydration time increased, it displayed the generation
of continuing ettringite.
