Table 1 Physical and chemical characteristics of scoria and pumice

SiO₂

52.46

64.92

Al₂O₃

18.14

10.82

Fe₂O₃

5.40

4.62

CaO

9.40

5.74

K₂O

0.20

4.26

Na₂O

3.28

4.92

MgO

7.44

0.92

MnO

0.12

0.20

P₂O₅

0.36

0.14

TiO₂

0.41

0.15

H₂O

1.12

0.85

LOI

2.08

3.67

pH

7.81

7.53

^aPhysical properties, particle size = 0.075–0.425 mm

Porosity (%)

36

73

Particle density (gcm⁻³)

2.96

2.33

Specific surface area (BET) (m² g⁻¹)

2.49

3.5

Cation exchange capacity (CEC), mequiv. 100 g⁻¹

0.09

0.84