to sulfate attack or damage by the heat of hydration.
Type I portland cement is used in pavement and
sidewalk construction, reinforced concrete buildings
and bridges, railways, tanks, reservoirs, sewers,
culverts, water pipes, masonry units, and soil-cement
Generally, it is more available than the
other types. Type I cement reaches its design strength
in about 28 days.
TYPE II. Type II cement is modified to resist
moderate sulfate attack. It also usually generates less
heat of hydration and at a slower rate than type I. A
typical application is for drainage structures where
the sulfate concentrations in either the soil or
groundwater are higher than normal but not severe.
type II cement is also used in large structures where
its moderate heat of hydration produces only a slight
temperature rise in the concrete. However, the
temperature rise in type II cement can be a problem
when concrete is placed during warm weather. Type
II cement reaches its design strength in about 45 days.
TYPE III. Type III cement is a high-early-
strength cement that produces design strengths at an
early age, usually 7 days or less. It has a higher heat
of hydration and is more finely ground than type I.
Type III permits fast form removal and, in cold
weather construction, reduces the period of protection
against low temperatures. Richer mixtures of type I
can obtain high early strength, but type III produces it
more satisfactorily and economically. However, use
it cautiously in concrete structures having a minimum
dimension of 2 1/2 feet or more. The high heat of
hydration can cause shrinkage and cracking.
TYPE IV. Type IV cement is a special cement.
It has a low heat of hydration and is intended for
applications requiring a minimal rate and amount of
heat of hydration.
Its strength also develops at a
slower rate than the other types. Type IV is used
primarily in very large concrete structures, such as
gravity dams, where the temperature rise from the
heat of hydration might damage the structure. Type
IV cement reaches its design strength in about 90
TYPE V. Type V cement is sulfate-resistant and
should be used where concrete is subjected to severe
sulfate action, such as when the soil or groundwater
contacting the concrete has a high sulfate content.
Type V cement reaches its design strength in 60 about
Air-entrained portland cement is a special cement
that can be used with good results for a variety of
conditions. It has been developed to produce concrete
that is resistant to freeze-thaw action, and to scaling
caused by chemicals applied for severe frost and ice
removal. In this cement, very small quantities of
air-entraining materials are added as the clinker is
being ground during manufacturing. Concrete made
with this cement contains tiny, well-distributed and
completely separated air bubbles. The bubbles are so
small that there may be millions of them in a cubic
foot of concrete. The air bubbles provide space for
freezing water to expand without damaging the
concrete. Air-entrained concrete has been used in
pavements in the northern states for about 25 years
with excellent results. Air-entrained concrete also
reduces both the amount of water loss and the
An air-entrained admixture may also be added to
types I, II, and III portland cement. The manufacturer
specifies the percentage of air entrainment that can be
expected in the concrete. An advantage of using
air-entrained cement is that it can be used and batched
like normal cement. The air-entrained admixture
comes in a liquid form or mixed in the cement. To
obtain the proper mix, you should add the admixture
at the batch plant.
The material combined with cement and water to
make concrete is called aggregate. Aggregate makes
up 60 to 80 percent of concrete volume. It increases
the strength of concrete, reduces the shrinking
tendencies of the cement, and is used as an
Aggregates are divided into fine (usually
consisting of sand) and coarse categories. For most
building concrete, the coarse aggregate consists of
gravel or crushed stone up to 1 1/2 inches in size.
However, in massive structures, such as dams, the
coarse aggregate may include natural stones or rocks
ranging up to 6 inches or more in size.