Civil Engineering Reference
In-Depth Information
Canadian CSA A5 cement Types 10, 20, 30, 40, and 50
are essentially the same as ASTM C 150 (AASHTO M 85)
Types I through V, respectively, except for the allowance of
up to 5% limestone in Type 10 and Type 30 cements.
The four types of blended hydraulic cements
addressed in CSA A362 are:
Portland blast-furnace slag cement (S)
Portland fly ash cement (F)
Portland silica fume cement (SF)
Ternary blend cement
The nomenclature and naming practice used for
Canadian blended cements is as follows:
TE-A/B
where
T = the equivalent performance to Type 10, 20, 30, 40,
or 50 portland cement;
E = an indication that the cement has equivalent
performance for the physical properties specified
in CSA A362, Table 2;
A = the predominant supplementary material; and
B = the secondary supplementary material, only spe-
cified in a ternary blend.
Examples:
10E-S a portland blast furnace slag cement having an
equivalent performance to that of a Type 10 portland
cement.
40E-F a portland fly ash cement having an equivalent
performance to that of a Type 40 portland cement.
50E-S/SF a ternary blend cement having an equivalent
performance to that of a Type 50 portland cement with slag
being the predominant supplementary cementing material
and silica fume the secondary supplementary cementing
material.
ponents of the raw mix to form four principal compounds
that make up 90% of cement by mass. Gypsum (4% to 6%),
or other calcium sulfate source, and grinding aids are also
added during grinding. Cement chemists use the following
chemical shorthand (abbreviations) to describe compounds:
A= Al
2
O
3
, C=CaO, F= Fe
2
O
3
, H=H
2
O, M=MgO, S= SiO
2
,
and … = SO
3
.
The term “phase” rather than “compounds” can also be
used to describe the components of clinker. Following are
the four primary compounds in portland cement, their ap-
proximate chemical formulas, and abbreviations:
Tricalcium silicate
3CaO•SiO
2
= C
3
S
Dicalcium silicate
2CaO•SiO
2
= C
2
S
Tricalcium aluminate
3CaO•Al
2
O
3
= C
3
A
Tetracalcium
aluminoferrite 4CaO•Al
2
O
3
•Fe
2
O
3
= C
4
AF
Following are the forms of calcium sulfate, their chem-
ical formulas, and abbreviations:
Anhydrous calcium
sulfate
CaSO
4
= CaO•SO
3
= C…
Calcium sulfate
dihydrate (gypsum)
CaSO
4
•2H
2
O =
CaO•SO
3
•2H
2
O= C…H
2
Calcium sulfate
hemihydrate CaSO
4
•
1
⁄
2
H
2
O =
CaO•SO
3
•
1
⁄
2
H
2
O= …H
1/2
Gypsum, calcium sulfate dihydrate, is the predomi-
nant source of sulfate used in cement.
C
3
S and C
2
S in clinker are also referred to as alite and
belite, respectively. Alite constitutes 50% to 70% of the
clinker, whereas belite accounts for only 15% to 30%.
Aluminate compounds constitute about 5% to 10% of the
clinker and ferrite compounds 5% to 15% (
Taylor 1997
).
These and other compounds may be observed and
analyzed through the use of microscopical techniques (see
Fig. 2-25, ASTM C 1356, and
Campbell 1999
).
CHEMICAL COMPOUNDS AND
HYDRATION OF PORTLAND CEMENT
During the burning operation in the manufacture of port-
land cement clinker, calcium combines with the other com-
Fig. 2-25. (left) Polished thin-section examination of portland clinker shows alite (C
3
S) as light, angular crystals. The darker,
rounded crystals are belite (C
2
S). Magnification 400X. (right) Scanning electron microscope (SEM) micrograph of alite (C
3
S)
crystals in portland clinker. Magnification 3000X. (54049, 54068)
