Concrete made with portland cement is
widely used as a construction material
because of its many favorable characteristics.
One of the most important is
a large strength-cost ratio in many applications.
Another is that concrete, while plastic, may be cast
in forms easily at ordinary temperatures to produce
almost any desired shape. The exposed face
may be developed into a smooth or rough hard
surface, capable of withstanding the wear of truck
or airplane traffic, or it may be treated to create
desired architectural effects. In addition, concrete
has high resistance to fire and penetration of water.
But concrete also has disadvantages. An important
one is that quality control sometimes is not so
good as for other construction materials because
concrete often is manufactured in the field under
conditions where responsibility for its production
cannot be pinpointed. Another disadvantage is
that concrete is a relatively brittle material—its tensile
strength is small compared with its compressive
strength. This disadvantage, however, can be offset
by reinforcing or prestressing concretewith steel. The
combination of the two materials, reinforced concrete,

possesses many of the best properties of each
and finds use in a wide variety of constructions,
including building frames, floors, roofs, and walls;
bridges; pavements; piles; dams; and tanks