Band, cm⁻¹

Phase

Relative intensity

Reference

OPC

Unfired

300˚C

450˚C

600˚C

750˚C

518

C₂S (O-Si-O)

Vs

W

s

s

s

s

[50] [51]

937

C₃S (Si-O)

Vs

W

m

m

s

s

[50] [51]

975

C-S-H (O-Si-O)

-

Vs

s

m

-

-

[50]

1115

Ettringite ( ${\text{SO}}_4^{2-}$ )

-

M

m

m

m

m

[49]

1144

Gypsum ( ${\text{SO}}_4^{2-}$ )

Vs

-

-

-

-

-

[49]

1432

Calcite ( ${\text{CO}}_3^{2-}$ )

Vs

M

s

m

m

w

[52]

1637, 3455

Free water (OH⁻)

-

S

vs

m

w

w

[53]

3642

Portlandite (OH⁻)

vw

S

vs

m

w

w

[50]