Improved Reactivity of Fly Ash-Slag Geopolymer by the Addition of Silica Fume
Table 4
Area obtained from deconvolution results and peak analysis of 29Si NMR spectroscopy (%).
Sample
Unreacted slag
C-S-H
Aluminosilicate
Signal (ppm)
−75
−79
(1Al) −81
−85
(4Al) −89
(3Al) −95
(2Al) −99
(1Al) −104
(0Al) −109
Slag
100
—
—
—
—
—
—
—
—
Fly ash
—
—
—
—
—
11.4
21.5
—
61.3
SF1
—
—
—
—
—
—
—
—
100
SF2
—
—
—
—
—
—
—
—
100
ZSF
—
—
—
—
—
—
—
—
100
C
22.4
—
20.4
7.2
10.4
5.4
1.2
18.3
14.6
SF1-10
27.2
11.5
—
11.3
12.6
9.7
5.5
7.6
14.6
SF1-20
27.5
0.5
—
22.0
8.6
10.5
8.3
5.4
17.2
Z10
0.92
12.0
17.6
11.2
11.6
8.6
3.5
3.3
23.0
HFA
22.3
—
22.7
5.0
15.6
—
10.8
6.7
16.9
Z10S
15.9
—
11.2
12.9
16.8
4.9
5.4
9.1
23.9
SF2-10
13.8
15.5
8.9
11.9
11.8
12.4
4.3
3.7
17.9
SF2-20
20.4
—
11.1
18.5
13.1
10.7
6.5
6.2
13.5
SF2-10S
15.0
4.4
9.4
11.2
8.9
19.8
5.9
3.6
21.9
SF2-20S
5.6
—
9.1
15.3
3.6
18.6
17.9
0.2
29.0
The peaks at −77, −75, and −69 ppm are attributed to the presence of raw slag in the geopolymer sample. These are the peaks above −109 ppm. Most of the peaks appearing above −108 ppm were assigned to different crystalline phases of silica ((0Al) signals) [18]. Fly ash has the signals related to (Al) as well as the signal (87 ppm) related to mullite (5.8%).
