READY MIX CONCRETE
Ready-mix concrete (RMC) is a type of concrete which is manufactured in
a cement factory, or specifically known as the batching plant, according to a
given set of proportions, and then delivered to a work site, by truck mounted
with mixers. This results in a precise mixture, allowing specialty concrete
mixtures to be developed and implemented on construction sites. The fist
factory which produced ready mix concrete was built in 1930s; however, the
industry didn’t begin to expand until late 80s. Since then it has continued to
grow significantly.
Ready mix concrete is sometimes preferred over on-site concrete mixing
because of the volume it can produce with precision of proportion of mixtures
and also due to reduced work site confusion. 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 termed as the customized concrete products
for commercial purpose. Ready-mix concrete (RMC) 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-mix concrete is
bought and sold by volume – usually expressed in cubic meters (cubic yards in
the US).
Ready-mix concrete is manufactured under controlled operations and
transported and placed at site using sophisticated equipment and methods. In
2011, there were 72,924 workers working in 2,223 companies that produced Ready
Mix Concrete in the United States.
Contents:
Process of Ready-mix concrete
Ready mix concrete has cement, aggregates, sand, water and other
chemicals, which are weigh- batched at a centrally located plant for a premium
quality. The concrete is then delivered to the construction site in transit
mixers and can be used straight away without any further treatment. The
automatic plant monitors weigh-batching, water-cement ratio, dosage of
admixture, moisture content, with precision to produce quality concrete.
All ingredients used for the preparation of ready mix concrete are
thoroughly tested for their quality and physical properties in a well equipped
laboratory attached to the plant for conformity to relevant international
standard codes. The moisture probe determines the water content in the sand and
aggregates. This accordingly helps in fixing the proportion of water to be
added for the preparation of the mix. Trial mixes are carried out and tested to
ensure that each and every batch of concrete coming out of the plant meets
various mix designs as per the client’s requirement with different grades of
concrete.
Advantages of ready-mix concrete
Following are the advantages of ready-mix concrete:
- Ready
Mix Concrete (RMC) allows speedy construction through programmed delivery
at site, mechanized operation with consequent economy.
- RMC
reduces the labour cost and site supervising cost.
- RMC
comes with consistency in quality through accurate & computerized
control of sand aggregates and water as per mix designs.
- Production
of RMC helps in minimizing cement wastage due to bulk handling.
- Production
of RMC is relatively pollution free.
- Reduced
project time resulting in savings in all aspects.
- Proper
control and economy in use of raw material resulting in saving of natural
resources.
Disadvantages of ready-mix concrete
Following are the disadvantages of ready-mix concrete:
- The
materials are batched at a central plant, and the mixing begins at that
very plant. So the travelling time from the plant to the site is critical
over longer distances. Some sites are just too far away, which can risk
that ready mix concrete may become unusable due to setting.
- It
will generate additional road traffic. Generally, Ready Mix Trucks are
large in size and may cover lot of area in the road blocking other
traffic. Furthermore, access roads
and site access have to be able to
carry the greater weight of the ready-mix truck plus load. (Green concrete
is approx. 2.5 tonne per m³.) This problem can be overcome by utilizing
so-called ‘mini mix’ companies which use smaller 4m³ capacity mixers able
to reach more-restricted sites.
- Concrete’s
limited time span between mixing and curing means that ready-mix should be
placed within 210 minutes of batching at the plant. Modern admixtures can
modify that time span precisely, however, the amount and type of admixture
added to the mix is very important.
Volumetric mobile mixer
Volumetric mobile mixer can provide a good alternative to ready-mix
concrete. This is a hybrid approach between ready-mix concrete and traditional
on-site mixing. The volumetric mobile mixer is a truck that contains concrete
ingredient materials and water to be mixed on the truck at the job site to make
and deliver concrete according to the amount needed. The on-truck mixing at the
job site eliminates the problems of ready-mix concrete such as delays that can
cause the pre-mixed concrete to become unusable.
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