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Concrete a composite man-made material, is the most widely used building material in the
construction industry. It consists of a rationally chosen mixture of binding material such as
lime or cement, well graded fine and coarse aggregates, water and admixtures (to produce
concrete with special properties). In a concrete mix, cement and water form a paste or matrix
which in addition to filling the voids of the fine aggregate, coats the surface of fine and coarse
aggregates and binds them together. The matrix is usually 22-34% of the total volume. Freshly
mixed concrete before set is known as wet or green concrete whereas after setting and hardening
it is known as set or hardened concrete. The moulded concrete mix after sufficient curing
becomes hard like stone due to chemical action between the water and binding material. It
would be impossible to discuss all the aspects of this material in few pages and the discussion
is confined to the general characteristics and quality tests necessary for its use by civil engineers
and architects.
Most of the ancient structures and historical buildings had been constructed with lime
concrete. With the advent of cement, the use of lime concrete has been confined to making
bases for concrete foundations and roof terracing. The major factors responsible for wide usage
of cement-concrete are mouldability, early hardening, high early compressive strength,
development of desired properties with admixtures to be used in adverse situations, suitability
for guniting, pumpability and durability. Most of the chapter is devoted to cement concrete
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