Chemical

composition

Sample

S1 (%)

S2 (%)

S3 (%)

S3 (%)

S4 (%)

Al₂O₃

93.9

88.9

88.6

85.2

84.0

SO₃

5.18

6.17

6.34

6.68

7.76

SiO₂

0.47

2.60

3.34

4.78

6.03

MgO

-

0.38

0.51

0.52

0.54

CaO

0.01

0.71

0.98

0.79

0.89

Fe₂O₃

0.02

0.06

0.08

0.07

0.07

Other

0.42

1.18

0.15

1.96

0.71