Ready-mix concrete is 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 in–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 1980s, 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.
Ready-mix concrete is also referred as the customized concrete products for commercial
purpose. Ready-mix 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. Read-mix concrete is bought and sold by volume - usually expressed in
cubic meters. Ready-mix concrete is manufactured under controlled
operations and transported and placed at site using sophisticated equipment and methods.
In 2011, there were 2,223 companies employing 72,924 workers that produced RMC in the United
States.
Standard ready-mix concrete vs. site-mix concrete A centralized concrete batching plant can
serve a wide area. Site-mix trucks can serve an even 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.
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 a technical issue. Generation of additional road traffic. Furthermore,
access roads and site access have to be able to carry the greater weight of the ready-mix
truck plus load. This problem can be overcome by utilizing so-called 'minimix' companies
which use smaller 4m³ capacity mixers able to reach more-restricted sites.
Concrete's limited timespan between mixing and going-off means that ready-mix should
be placed within 210 minutes of batching at the plant. Modern admixtures can modify that
timespan precisely, however, so the amount and type of admixture added to the mix is
very important. See also
Types of concrete References
Notes ^ "Ready Mix Concrete Industry". PellResearch.com.
^ ASTM C 94 and AASHTO M 157 Bibliography
Panarese, William C.; Kosmatka, Steven H.; Kerkhoff, Beatrix. "10". Design and Control
of Concrete Mixtures. Skokie, Illinois: Portland Cement Association. ISBN 0-89312-217-3.
External links National Ready Mixed Concrete Association