Thursday 8 March 2012

Ready-mix concrete

Ready-mix concrete is a type of concrete that
is manufactured in a factory or batching plant,
according to a set recipe, and then delivered to
a work site, by truck mounted transit mixers .
This results in a precise mixture, allowing
specialty concrete mixtures to be developed and
implemented on construction sites. The first
ready-mix factory was built in the 1930s, but
the industry did not begin to expand
significantly until the 1960s, and it has
continued to grow since then.
Ready-mix concrete is sometimes preferred
over on-site concrete mixing because of the
precision of the mixture and reduced work site
confusion. However, using a pre-determined
concrete mixture reduces flexibility, both in the
supply chain and in the actual components of
the concrete.
The leading ready-mix concrete supplier
worldwide is the Mexican concrete company
Cemex ; its main competitor is France -based
Lafarge and the leading ready-mix concrete
supplier in Middle East is the Unibeton Ready
Mix.
Ready Mixed Concrete is also referred as the
customized concrete products for commercial
purpose. the Ready-mix Concrete Company
offer different concrete according to user's mix
design or industrial standard.
The Ready mixed concrete company is required
to equip themselves with up-to-date
equipments, such as transit mixer, concrete
pump, and Concrete Batching Plant, which
needs visualized production management
software and also PLC controller.
Ready Mixed Concrete, or RMC as it is popularly
called, refers to concrete that is specifically
manufactured for delivery to the customer's
construction site in a freshly mixed and plastic
or unhardened state. Concrete itself is a mixture
of Portland cement, water and aggregates
comprising sand and gravel or crushed stone. In
traditional work sites, each of these materials is
procured separately and mixed in specified
proportions at site to make concrete. Ready
Mixed Concrete is bought and sold by volume -
usually expressed in cubic meters. RMC can be
custom-made to suit different applications.
Ready Mixed Concrete is manufactured under
computer-controlled operations and
transported and placed at site using
sophisticated equipment and methods. RMC
assures its customers numerous benefits.
Standard Ready mix Concrete -VS- Site
mix Concrete
A centralized concrete batching plant can
serve a wide area. Site Mix trucks can serve a
larger area including remote locations that
standard trucks can not.
The plants are located in areas zoned for
industrial use, and yet the delivery trucks can
service residential districts or inner cities. Site
Mix trucks have the same capabilities.
Better quality concrete is produced. Site Mix
can produce higher compression strength with
less water then standard batching methods.
Elimination of storage space for basic
materials at site. Standard Batch plant need
more room for their operation than Site Mix
trucks.
Elimination of procurement / hiring of plant
and machinery
Wastage of basic materials is avoided. With a
Site Mix truck, there is less waste and wash
out. This is better for the environment.
Labor associated with production of concrete
is eliminated. It takes more people to operate
a standard batch plant than a Mobile Mix
truck.
Time required is greatly reduced. One Mobile
mix truck can produce 8 yards of concrete in 8
minutes. It can also operate continuously
without needing to be moved away from the
pump truck. One Mobile mix truck can
produce 460 yards of concrete in an 8 hour
shift. Where standard trucks must stop and
move off the pump to bring in the next truck.
So to deliver the same amount of concrete it
will take nearly 3 more hours with a standard
truck. This will increase labor cost.
Disadvantages of Ready-Mix Concrete
The materials are batched at a central plant,
and the mixing begins at that plant, so the
traveling time from the plant to the site is
critical over longer distances. Some sites are
just too far away, though this is usually a
commercial rather than technical issue.
Generation of additional road traffic;
furthermore, access roads, and site access
have to be able to carry the weight of the
truck and load. Concrete is approx. 2.5tonne
per m³. This problem can be overcome by
utilizing so-called 'minimix' companies, using
smaller 4m³ capacity mixers able to access
more restricted sites.
Concrete's limited timespan between mixing
and going-off means that readymix should be
placed within 10 minutes of batching at the
plant. Modern additives modify precisely that
timespan however, the amount of additive
added to the mix is very important.

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