H y d r a t i o n P r o p e r t i e s o f I n o r g a n i c B i n d e r
669
2.2 Using Materials
Electric arc furnace reducing slag(EAF reducing slag) used in the experiment was
rapidly cooled down in the air jet type in the melting slag status, and it pulverizes.
Analysis of oxide and physical properties of reducing slag powder are compared with
those of Ordinary Portland Cement(hereinafter "OPC") and Regulated Set Cement(RSC)
as shown in Table 2. To obtain the workability of RSC and RC EAFRS powder, citric acid
setting retarder was diluted in mixing water in 0.5% compared to weight.
Table 2: Physical and chemical properties of experiment materials
Binder
Physical properties
Oxide content(Wt.%)
Density(g/
㎣
) Fineness(
㎠
/g) SiO
2
CaO Al
2
O
3
Fe
2
O
3
MgO MnO
OPC
3.15
3,200
17~25 60~67 3~8 0.5~6 0.1~4
-
RSC
2.87
4,800
10~16 47~53 14~20 3.0
2.5
-
EAFRS
2.97
5,500
10.9
44.5
26.6
4.3
6.6
0.6
2.3 Experimental Methods
As paste experiment, setting time test was conducted according to ‘KS L 5108,Testing
method for setting time of hydraulic cement by vicat needle’. To check the stability for
expansion by f-CaO of reducing slag, stability test was conducted with 2 standards of KS
and JIS such as ‘KS L 5107, Testing method for autoclave expansion of portland cement’
and ‘JIS R 5201 Physical test method of cement’.
As mortar experiment, strength test was conducted according to ‘KS L ISO 679, Methods
of testing cements-Determination of strength’, and length variation test was conducted
according to ‘KS F 2424, Testing method for length change of mortar and concrete’.
3. Results and Discussion
3.1 Principal componentanalysis
Figure 1 is the CSA constitutional diagram, which is made by content of oxide of RC
EAFRS powder shown in Table 2. It shows that RC EAFRS powder is located in a place
similar to regulated set cement. In Figure 2, the result of measurement of XRD for
mineral analysis of slowly cooled EAFRS powder, it’s found that C
12
A
7
and C
2
S,
representing rapid set characteristics contained in regulated set cement, are generated.
However, as slowly cooled EAFRS is slowly cooled in the molten state, the reactivity of
C
12
A
7
of rapid set characteristics gets lower, and C
2
S is also displaced to Shannoite (γ-
C
2
S), which doesn’t have reactivity. When EAFRS is rapidly cooled, however, C
12
A
7
has
rapid set characteristic, and C
2
S retains Larnite (β-C
2
S), which has reactivity. Mayenite
and Larnite of RC cooled EAFRS can be identified through SEM. Fig. 3 is SEM
measured after etching RC cooled EAFRS on the surface in the solution of NH
4
Cl 1%,
indicating that the part forming circle is C
2
S and the other part which encircles C
2
S is on
C
12
A
7
through EDS. The findings of EDS measurement of the two minerals shown in Fig.
3 are described in Table 3. Mayenite, the rapid set mineral, attributes its characteristics
to high CaO content of EAFRS and Al
2
O
3
.
