w
2
2w2g
Es2g IRWThe CaO available to combine with SiO 2 is total CaO minus (free CaO + c 1 + c 2 + c 3 ); call this
difference c. Then the total silica (s) is calculated first to combine with CaO to form C 2 S. Since
the ratio 2CaO SiO 2 : SiO 2 = 172.20 : 60.06 = 2.87:1, each percentage of s × 2.87 is the percentage
of C 2 S. This first approximation of C 2 S is entered in column 8, opposite SiO 2. By subtracting this
value of C 2 S from the sum s + c, the amount of CaO (called c 4 ) available for combination with
2CaO SiO 2 to form 3CaO SiO 2 is determined. Since the ratio 3CaO SiO 2 :CaO = 228.27:56.07
= 4.07:1, multiplying c 4 by 4.07 gives the amount of C 3 S which is entered at the foot of column
- By subtracting this value of C 3 S from c + s, the true percentage of C 2 S is found and entered
in column 8.
Should the computed percentage of C 3 S be greater than c + s, no C 2 S is present. In that case
the content of C 3 S is found from the ratio 3CaO SiO 2 : SiO 2 = 228.27 : 60.06 = 3.8 : 1. Hence, the
percentage of C 3 S is obtained by multiplying the percentage of SiO 2 by 3.8. This latter value of
C 3 S, subtracted from c + s, gives the percentage of uncombined lime. This last condition can
only be obtained when lime is in excess of the amount required for equilibrium and the free
lime has not been deducted.
Since errors in chemical analysis of 0.2 per cent in determinations of lime, alumina, silica, or
iron oxide will make errors up to 1.5 per cent in certain compounds, percentages for the
compounds should be rounded off to whole numbers. If the ignition loss is high, the analysis
should be reduced to a clinker basis prior to compound calculations.
As previously mentioned, Bogue's method of calculation is based on the assumption that the
clinker is slowly cooled at such rate that equilibrium is maintained and the crystallization is
complete. Lea and Parker have shown that values calculated by the bogue method may be
considerably in error if the clinker liquid crystallizes independently o f the solids formed, or if
cooling is so sudden that no crystallization takes place and glass is formed. For the case of
independent crystallization and a clinkering temperature of 1400°C, they show that Bogue's
method is correct for cements with Al 2 O 3 /Fe 2 O 3 ratios between 0.9 and 1.7, but for ratios
between 1.7 and 6.1 their corrections to be added are :
C 3 S, + (1.8Al 2 O 3 – 2.8Fe 2 O 3 )
C 2 S, + (2.1Fe 2 O 3 – 1.4Al 2 O 3 )
C 3 A, + (2.5Fe 2 O 3 – 1.6Al 2 O 3 )
C 4 AF, Nil
Thus for a cement with Al 2 O 3 = 7 and Fe 2 O 3 = 3 per cent, the correction to C 3 S = 4.2, to
C 2 S = –3.5, and to C 3 A = –3.7 per cent.
For very rapid cooling of the clinker, the liquid is formed into glass and they show that no
C 3 A or C 4 AF appear but the amount of glass is + (2.95Al 2 O 3 + 2.2Fe 2 O 3 ). For this case their
corrections to Bogue's values for C 3 S and C 2 S are: C 3 S, + (1.8Al 2 O 3 – 2.8Fe 2 O 3 ); C 2 S + (1.9Fe 2 O 3
- 2.1Al 2 O 3 ).
SS rhesyx2yp2giwix
The chemical reaction between cement and water is known as hydration of cement. The reaction
takes place between the active components of cement (C 4 AF, C 3 A, C 3 S and C 2 S) and water. The