Concrete
is a construction material composed of cement (commonly Portland cement) as
well as other cementitious materials such as fly ash and slag cement,aggregate
(generally a coarse aggregate such as gravel limestone or granite, plus a fine
aggregate such as sand), water, and chemical admixtures. The word concrete
comes from the Latin word "concretus", which means
"hardened" or "hard".
Concrete
solidifies and hardens after mixing with water and placement due to achemical
process known as hydration. The water reacts with the cement, which bonds the
other components together, eventually creating a stone-like material. Concrete
is used to make pavements, architectural structures,
foundations,motorways/roads, bridges/overpasses, parking structures,
brick/block walls andfootings for gates, fences and poles.
More
concrete is used than any other man-made material in the world.[1] As of 2006,
about 7 cubic kilometres of concrete are made each year—more than one cubic
metre for every person on Earth. Concrete powers a $US 35-billion industry
which employs more than two million workers in the United Statesalone.[citation
needed] More than 55,000 miles (89,000 km) of highways in America are paved
with this material. The People's Republic of China currently consumes 40% of
the world's cement/concrete production.
A
superplasticizer is one of a class of admixtures called water-reducers that are
used to lower the mix water requirement of concrete. Normal water-reducers
based on lignosulphonic acids, hydroxycarboxylic acids or processed
carbohydrates are capable of reducing water requirements by about 10 to 15 per
cent. Incorporating larger amounts to produce higher water reductions results
in undesirable effects on setting, air content, bleeding, segregation and
hardening characteristics. Superplasticizers are chemically different from
normal water-reducers, and are capable of reducing water contents by about 30
per cent. They are variously known as superplasticizers, superfluidizers,
superfluidifiers, super water-reducers or high range water-reducers. Since they
were first introduced in Japan about 15 years ago they have been used to
produce several million cubic metres of concrete; in the construction of the
Olympic stadium in Montreal alone, 5000 precast concrete units were produced
utilizing superplasticizers.
The
basic advantages of superplasticizers include, (1) high workability of
concrete, resulting in easy placement without reduction in cement content and
strength; (2) high strength concrete with normal workability but lower water
content; and (3) a concrete mix with less cement but normal strength and
workability. So if you are looking for concrete and construction material
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