Civil Engineering Reference
In-Depth Information
Expansive Cements
Expansive cement is a hydraulic cement that expands
slightly during the early hardening period after setting. It
must meet the requirements of ASTM C 845 in which it is
designated as Type E-1. Currently, three varieties of expan-
sive cement are recognized and have been designated as K,
M, and S, which are added as a suffix to the type. Type E-
1(K) contains portland cement, tetracalcium trialuminosul-
fate, calcium sulfate, and uncombined calcium oxide
(lime). Type E-1(M) contains portland cement, calcium
aluminate cement, and calcium sulfate. Type E-1(S) con-
tains portland cement with a high tricalcium aluminate
content and calcium sulfate. Type E-1(K) is the most read-
ily available expansive cement in North America.
Expansive cement may also be made of formulations
other than those mentioned. The expansive properties of
each type can be varied over a considerable range.
When expansion is restrained, for example by reinforc-
ing steel, expansive cement concrete (also called shrinkage
compensating concrete) can be used to (1) compensate for
the volume decrease due to drying shrinkage, (2) induce
tensile stress in reinforcement (post-tensioning), and (3)
stabilize the long-term dimensions of post-tensioned
concrete structures with respect to original design.
One of the major advantages of using expansive
cement in concrete is noted in (1) above; when you can
compensate for volume change due to drying shrinkage
you can control and reduce drying shrinkage cracks. Fig.
2-23 illustrates the length change (early expansion and
drying shrinkage) history of shrinkage-compensating
concrete and conventional portland cement concrete. For
more information see
Pfeifer and Perenchio (1973)
,
Russell
(1978)
, and
ACI (1998)
.
Oil-Well Cements
Oil-well cements, used for oil-well grouting, often called
oil-well cementing, are usually made from portland cement
clinker or from blended hydraulic cements. Generally they
must be slow-setting and resistant to high temperatures
and pressures. The American Petroleum Institute's
Specification for Cements and Materials for Well Cementing
(API Specification 10A) includes requirements for eight
classes of well cements (Classes A through H) and three
grades (Grades O—ordinary, MSR—moderate sulfate
resistant, and HSR—high sulfate resistant). Each class is
applicable for use at a certain range of well depths, temper-
atures, pressures, and sulfate environments. The petroleum
industry also uses conventional types of portland cement
with suitable cement-modifiers. Expansive cements have
also performed adequately as well cements.
Cements with Functional Additions
Functional additions can be interground with cement
clinker to beneficially change the properties of hydraulic
cement. These additions must meet the requirements of
ASTM C 226 or C 688. ASTM C 226 addresses air-entrain-
ing additions while ASTM C 688 addresses the following
types of additions: water-reducing, retarding, accelerating,
water-reducing and retarding, water-reducing and acceler-
ating, and set-control additions. Cement specifications
ASTM C 595 (AASHTO M 240) and C 1157 allow functional
additions. These cements can be used for normal or special
concrete construction, grouting, and other applications.
Gajda (1996)
studied a functional addition to control alkali-
silica reactivity.
Water-Repellent Cements
Water-repellent cements, sometimes called waterproofed
cements, are usually made by adding a small amount of
water-repellent additive such as stearate (sodium, alumi-
num, or other) to cement clinker during final grinding (
Lea
1971
). Manufactured in either white or gray color, water-
repellent cements reduce capillary water transmission
when there is little to no pressure but do not stop water-
vapor transmission. They are used in tile grouts, paint, and
stucco finish coats.
0.10
Moist-cured for 7 days, followed by
air drying at 23
F)
Restrained by reinforcing steel, p = 0.35%
C (73
°
°
0.08
0.06
Shrinkage-compensating
concrete
0.04
0.02
Regulated-Set Cements
Regulated-set cement is a calcium fluoroaluminate
hydraulic cement that can be formulated and controlled to
produce concrete with setting times from a few minutes to
an hour and with corresponding rapid early strength
development (
Greening and others 1971
). It is a portland-
based cement with functional additions that can be manu-
factured in the same kiln used to manufacture conventional
portland cement. Regulated-set cement incorporates set
control and early-strength-development components. Final
physical properties of the resulting concrete are in most
0
-0.02
Portland cement
concrete
-0.04
-0.06
0 7 50 100 150 200
Time, days
Fig. 2-23. Length-change history of shrinkage compensating
concrete containing Type E-1(S) cement and Type I portland
cement concrete (
Pfeifer and Perenchio 1973
).
