Portland, Blended, and Other Hydraulic Cements - Design and Control of Concrete Mixtures - page 42

Table 2-6. Chemical and Compound Composition and Fineness of Cements*

Type of Chemical composition, % Potential compound composition,% Blaine
portland fineness,
cement SiO 2 Al 2 O 3 Fe 2 O 3 CaO MgO SO 3 Na 2 O eq C 3 S 2 S 3 A 4 AF m 2 /kg
I (min-max) 18.7-22.0 4.7-6.3 1.6-4.4 60.6-66.3 0.7-4.2 1.8-4.6 0.11-1.20 40-63 9-31 6-14 5-13 300-421
I (mean) 20.5 5.4 2.6 63.9 2.1 3.0 0.61 54 18 10 8 369
II** (min-max) 20.0-23.2 3.4-5.5 2.4-4.8 60.2-65.9 0.6-4.8 2.1-4.0 0.05-1.12 37-68 6-32 2-8 7-15 318-480
II** (mean) 21.2 4.6 3.5 63.8 2.1 2.7 0.51 55 19 6 11 377
III (min-max) 18.6-22.2 2.8-6.3 1.3-4.9 60.6-65.9 0.6-4.6 2.5-4.6 0.14-1.20 46-71 4-27 0-13 4-14 390-644
III (mean) 20.6 4.9 2.8 63.4 2.2 3.5 0.56 55 17 9 8 548
IV (min-max) 21.5-22.8 3.5-5.3 3.7-5.9 62.0-63.4 1.0-3.8 1.7-2.5 0.29-0.42 37-49 27-36 3-4 11-18 319-362
IV (mean) 22.2 4.6 5.0 62.5 1.9 2.2 0.36 42 32 4 15 340
V (min-max) 20.3-23.4 2.4-5.5 3.2-6.1 61.8-66.3 0.6-4.6 1.8-3.6 0.24-0.76 43-70 11-31 0-5 10-19 275-430
V (mean) 21.9 3.9 4.2 63.8 2.2 2.3 0.48 54 22 4 13 373
White (min-max) 22.0-24.4 2.2-5.0 0.2-0.6 63.9-68.7 0.3-1.4 2.3-3.1 0.09-0.38 51-72 9-25 5-13 1-2 384-564
White (mean) 22.7 4.1 0.3 66.7 0.9 2.7 0.18 63 18 10 1 482
* Values represent a summary of combined statistics. Air-entraining cements are not included. For consistency in reporting, elements are
reported in a standard oxide form. This does not mean that the oxide form is present in the cement. For example, sulfur is reported as SO 3 ,
sulfur trioxide, but, portland cement does not have sulfur trioxide present. “Potential Compound Composition” refers to ASTM C 150
(AASHTO M 85) calculations using the chemical composition of the cement. The actual compound composition may be less due to incom-
plete or altered chemical reactions.
** Includes fine grind cements.
Adapted from PCA (1996) and Gebhardt (1995) .

setting, as well as drying shrinkage and strength gain ( Tang
1992 ). Minor and trace elements and their effect on cement
properties are discussed by Bhatty (1995) and PCA (1992) .
Present knowledge of cement chemistry indicates that the
primary cement compounds have the following properties:
Tricalcium Silicate, C 3 S, hydrates and hardens rapidly
and is largely responsible for initial set and early strength
(Fig. 2-29). In general, the early strength of portland cement
concrete is higher with increased percentages of C 3 S.

Dicalcium Silicate, C 2 S, hydrates and hardens slowly and
contributes largely to strength increase at ages beyond one
week.
Tricalcium Aluminate, C 3 A, liberates a large amount of
heat during the first few days of hydration and hardening.
It also contributes slightly to early strength development.
Cements with low percentages of C 3 A are more resistant to
soils and waters containing sulfates.
Tetracalcium Aluminoferrite, C 4 AF, is the product result-
ing from the use of iron and aluminum raw materials to
reduce the clinkering temperature during cement manu-
facture. It contributes little to strength. Most color effects
that make cement gray are due to C 4 AF and its hydrates.
Calcium Sulfate, as anhydrite (anhydrous calcium sul-
fate), gypsum (calcium sulfate dihydrate), or hemihydrate,
often called plaster of paris or bassanite (calcium sulfate
hemihydrate) is added to cement during final grinding to
provide sulfate to react with C 3 A to form ettringite (calcium
trisulfoaluminate). This controls the hydration of C 3 A.
Without sulfate, a cement would set rapidly. In addition to
controlling setting and early strength gain, the sulfate also
helps control drying shrinkage and can influence strength
through 28 days ( Lerch 1946 ).
In addition to the above primary cement compounds,
numerous other lesser compound formulations also exist
( PCA 1997 , Taylor 1997 , and Tennis and Jennings 2000 ).

100%

80%

60%

C 3 S

40%

C 2 S

C 3 A
C 4 AF
Overall

20%

0%

Water (Evaporable and Nonevaporable)

0 20 40 60 80 100

Age, days

Water is a key ingredient of pastes, mortars, and concretes,
as the phases in portland cement must chemically react
with water to develop strength. The amount of water
added to a mixture controls the durability as well. The

Fig. 2-29. Relative reactivity of cement compounds. The
curve labeled “overall” has a composition of 55% C 3 S, 18%
C 2 S, 10% C 3 A, and 8% C 4 AF, an average Type I cement
composition ( Tennis and Jennings 2000 ).