TM 5-822-7/AFM 88-6, Chap. 8
ECE-G) or the appropriate Air Force major command.
characteristics of freshly mixed concrete and is
required for the freezing and thawing resistance of
When concrete proportioning is the responsibility of
hardened concrete. The use of entrained air in
the contractor and the cement content is less than
concrete will reduce strength, but because of the
470 pounds per cubic yard, the results should be
improved workability in the freshly mixed concrete,
verified by two Corps of Engineers Division
adjustments in aggregate proportions and reduction
laboratories or commercial laboratories prior to
of water are normally possible that will negate or at
submittal. The results of mixture proportioning
least minimize the loss of strength. Proper propor-
studies for proposed aggregates and cements and
tioning and control of the air-entrained concrete
the results of qualitative tests on aggregates and on
mixture are essential in order to derive maximum
resulting concretes will be submitted with requests
benefits from improvement in the placability and
for approval.
durability of concrete with a minimum effect on
flexural strength.
4. Cement.
(2.) Percentage of air content. The specified air
a. Five portland cements designated as Types I
content will be 6 1 percent for concrete
through V are marketed today. ASTM C 150 provides
a detailed specification for these cements. Type I
pavements located in regions where resistance to
portland cement is common or ordinary cement that
freezing and thawing is a prime consideration, and
is supplied unless another type is specified. Type II
will be 5 1 percent for concrete pavements
is modified portland cement that provides moderate
located in regions where frost action is not a factor
resistance against sulfate attack and a lower heat of
and air entrainment is used primarily to improve the
hydration than Type I cement. It is common for
workability and placability of freshly mixed concrete.
cement to be manufactured to meet the physical and
Air content will be controlled in the field at the point
chemical requirements of both Type I and II cements.
within the specified range most appropriate for local
b. Type III cement is high early-strength cement.
conditions depending upon the severity of exposure
Ultimate strength is about the same as Type I
and the quality and maximum size of aggregate. If
cement, but Type III cement has a 3-day compressive
slag aggregate is used, the air content will be deter-
strength approximately equal to the Type I
mined by the volumetric method as described in
cement's 7-day strength. The cost of Type III
ASTM C 173. Where the aggregate is of compara-
cement in lieu of Types I or II cement can only be
tively poor quality or when the maximum size is 1%
justified when early strength gain is needed to open
inches or less, the air content will be controlled at 6
pavements to traffic or the high heat of hydration is
1 percent. In such instances, where resistance to
needed for cool construction periods. Type IV
freezing and thawing is not a prime consideration,
cement has a low heat of hydration that may be
the air content will be 5 1 percent. If further
useful in mass concrete but is not likely to be
reduction in the air content or the use of non-air-
encountered in pavement construction. Type V
entrained concrete is necessary, prior approval will
sulfate-resistant cement should be used when the
be obtained from HQDA (DAEN-ECE-G), Wash-
concrete will be exposed to severe sulfate attack.
ington, DC 20314-1000 or the appropriate Air Force
The potential for severe sulfate attack exists when
major command.
the concrete is exposed to water-soluble sulfate in
e. Cement content. Either the contractor or the
soil or water in excess of 0.20 percent or 1,500 parts
contracting officer may be responsible for mixture
per million. The potential for moderate sulfate
proportioning. When the contractor is responsible
attack exists for sulfate contents in excess of 0.10,
for mixture proportioning, no separate payment will
or 150 parts per million.
be made for cement. When the contracting officer is
c. High alumina cement, also known as aluminous
responsible for mixture proportioning, no limits for
or calcium aluminate cement, gains most of its
the quantity of cement content will be included in
strength in one day, has a high exotherm, is resistant
the contract specifications; the quantity of cement
to chemical attack, and is a refractory material.
used per cubic yard of concrete will be determined
When exposed to warm, moist conditions, it will
by the contracting officer, and cement will be paid
undergo a long-term strength loss. High alumina
for under a separate bid item. When the concrete
cement may find some specialized applications in
proposed for use on a paving project has a cement
pavement construction where its rapid strength
content of less than 470 pounds per cubic yard, prior
gain, high exotherm, or refractory properties
approval will be obtained from HQDA (DAEN-
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