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READY MIX CONCRETE
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1.0 Introduction:-
• Few things are more aggravating to produce on a worksite than concrete. Bags of cement,
sand, aggregate (gravel) and possibly other additives must be delivered to the construction
area. A supply of clean water is also necessary, along with a rented concrete mixing hopper.
• Even after all the dusty and heavy ingredients have been loaded into the hopper, one small
error in the wet/dry ratio can render an entire batch of concrete unusable. One common
solution to this messy and time-consuming problem is “READY MIX CONCRETE”
• Ready-mix concrete (RMC) is a ready-to-use material, with predetermined mixture of
cement, sand, aggregates and water. RMC is a type of concrete manufactured in a factory
according to a set recipe or as per specifications of the customer, at a centrally located
batching plant.
• It is delivered to a worksite, often in truck mixers capable of mixing the ingredients of the
concrete en route or just before delivery of the batch.
• This results in a precise mixture, allowing specialty concrete mixtures to be developed and
implemented on construction sites.
• The second option available is to mix the concrete at the batching plant and deliver the mixed
concrete to the site in an agitator truck, which keeps the mixed concrete in correct form. In
the case of the centrally mixed type, the drum carrying the concrete revolves slowly so as to
prevent the mixed concrete from "segregation" and prevent its stiffening due to initial set.
• The use of the RMC is facilitated through a truck-mounted 'boom placer' that can pump the
product for ready use at multi-storied construction sites. A boom placer can pump the
concrete up 80 meters.
• RMC is preferred to on-site concrete mixing because of the precision of the mixture and
reduced worksite confusion. It facilitates speedy construction through programmed delivery
at site and mechanized operation with consequent economy.
• It also decreases labour, site supervising cost and project time, resulting in savings. Proper
control and economy in use of raw material results in saving of natural resources. It assures
consistent quality through accurate computerized control of aggregates and water as per mix 2
designs. It minimizes cement wastage due to bulk handling and there is no dust problem and
therefore, pollution-free.
• Ready mix concrete is usually ordered in units of cubic yards or meters. It must remain in
motion until it is ready to be poured, or the cement may begin to solidify. The ready mix
concrete is generally released from the hopper in a relatively steady stream through a trough
system. Workers use shovels and hoes to push the concrete into place.
• Some projects may require more than one production run of ready mix concrete, so more
trucks may arrive as needed or additional batches may be produced offsite and delivered.
• However there are some disadvantages of RMC to, like double handling, which results in
additional cost and losses in weight, requirement of god owns for storage of cement and large
area at site for storage of raw materials.
• Aggregates get mixed and impurities creep in because of wind, weather and mishandling at
site. Improper mixing at site, as there is ineffective control and intangible cost associated
with unorganized preparation at site are other drawbacks of RMC.
• There are always possibilities of manipulation; manual error and mischief as concreting are
done at the mercy of gangs, who manipulate the concrete mixes and water cement ratio.
• The first ready-mix factory, which was built in the 1930s, remained in a standstill position till
1960s, but continued to grow since then.
2.0 History:-
• Ready mix concrete was first patented in Germany in 1903; its commercial delivery was
not possible due to lack of transportation needs.
• The first commercial delivery was made in Baltimore USA in 1913.The first revolving
drum type transit mixer was developed in 1926. In 1931, a RMC plant was set up for the
construction of Heathrow airport, London.
• In the mid 90’s there were about 1100 RMC plants in UK consuming about 45% of
cement produced in that country. In Europe in 1997 there were 5850 companies
producing a total of 305 million cusecs of RMC. In USA by 1990, around 72% (more
than 2/3rd) of cement produced was being used by various RMC plants. In Japan first
RMC plant was set up in 1949. By 1992 Japan was the then largest producer of RMC,
producing 18196 million tons of concrete. In many other countries of the world including
some of the developing countries like Taiwan, Malaysia etc, RMC industry is well
developed.
Development in India
• In India RMC was first initially was used in 1950 during the construction sites of Dams
like likeBhakraNangal, Koyna. At the construction the transportation of concrete is done
by either manually or mechanically using ropeways &buckets or conveyor systems. RMC
at Pune in the year 1991. However, due to various pit falls and problems this plant did not
survive for long and was closed. Within a couple of months in the year 1993, two RMC
plants were set up in Mumbai to commercially sell RMC to the projects where they were
installed. Unitech Construction set up one plant at Hiranandani Complex and Associated
Cement Companies set up another plant at Bharat Diamond Bourse Commercial
Complex.
• The first concrete mixed off site and delivered to a construction site was effectively done
in Baltimore, United States in 1913 just before the First World War.
• The increasing availability of special transport vehicles, supplied by the new and fast -
growing automobile industry, played a positive role in the development of RMC industry. 4
3.0 Scope of Ready Mixed Concrete Plant:-
• Long, Long years ago, their where simple houses but in 21st century we can see houses
constructed in R.C.C.
• Therefore concrete got more importance than any other construction material. So the use
of concrete is increasing day by day.
• For construction most of the contractors and builders have to collect the raw materials
required for the construction before starting actual works. These materials should be
stored at the site properly. This technique can be possible when there will be more empty
space at the construction site which is not possible in congested areas. At this time there
is one solution to overcome all these problems that is nothing “READYMIX
CONCRETE”.
By using R.M.C we can save time and money required for the labours. In
following places ready mix concrete can be used:-
1. Major concerting projects like dams, roads, bridges, tunnels, canals etc.
2. for concreting in congested areas where storage of materials is not possible.
3. Sites where intensity of traffic makes problems.
4. When supervisor and labour staff is less.
5. To reduce the time required for construction etc.
6. Huge industrial and residential projects.
4.0 Details of Plant Visited Site:-
• Address of the Plant Visited Site: -
Innovative Infrastructure, Ready mixed concrete,
Opp. Ekta Hotel,
Sarkhej, Ahmedabad.
• Time of Establishment:
- 02/06/2006
• Authority People
: -
(1) Mr. Harishbhai Gohil
(2) Mr. Natubhai Gohil
• Area of Plant
: - Minimum area is 3500 yard
• Timing:
- 24 hours working
Project name
• Tesla Pronestyl, Shantipura Choki
• Per Day 200 m3
Concrete Supplied
• About 5 km from Plant
6.0 Equipment Required in R. M. C.:-
Following are the equipment’s required in R.M.C
1. Batching plant
2. Silos
3. Belt Conveyor
4. Transit mixer
BATCHING
Batching plants are classified as
1. Manual
2. Semiautomatic
3. Fully automatic
Storage
Storage of the raw materials is done by following methods: -
Inline Bins
Inert raw materials like fine & coarse aggregates are stored in bins called as “Inline Bins” where
the trucks carrying fine & coarse aggregate can dump the material easily. The aggregates
required are fed by the means of aggregate belt conveyer. On the aggregate belt conveyer the
aggregates are weighed automatically by means of computer form the computer room presents
on the plant.
Technical Specifications of Silos
1. Size - 3200mm Dia x 14 mts of Total Height.
2. Side shell thickness - 5mm/6mm thick of sail / VSP/ SSP / Standard make of M.S plate.
3. Bottom cone - 6mm/8mm /10mm thick of above make as per customer requirements.
4. Safety handrail on top will be provided.
5. Maintenance ladder with safety gage provided from bottom to top.
6. Bottom leg pipe should be ERW / Seamless type of TATA / JINDAL Make Of heavy
duty type.
7. Total silo should be two coat Red Oxide & Two coat finish enamel paint or sand blasting
as per customer’s requirements with Asian paints or Berger make etc.
8. Provision will be provided for fixing of silo accessories.
9. Pipe line fittings will be provided with flanges for easy dismantling.
10. Double structure platform will be provided for fly ash storage solos.
Aggregate Feeding Belt Conveyors
• Manufactured and Supplied high quality Aggregate Feeding Belt Conveyors for Handling
Sand, Jally, Stones (Aggregates) to RMC batching Plant.
• Capacities from 18 M3
to 300 M3
of various types like Compartment, In Line Silo, Four
Bin Type, Mobile etc.
• Products are made by using very high quality Structural raw material make of VSP, SSP,
TATA, JINDAL STEELS; standard suppliers make for drive unit, Belt etc.
• Also providing Heavy Duty Rollers & Pulleys which ensures hassle free and long life
work performance.
• These Aggregate Feeding Belt Conveyors are widely available in various specifications
and dimensions like 650 MM to 1200 MM wide. 23
7.0 Merits & Demerits of Ready-Mix Concrete:-
Merits of Ready-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 cannot.
• 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 than 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.
Demerits of Ready-Mix Concrete
• The materials are batched at a central plant, and the mixing begins at that plant, so the
travelling 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 has 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 time span between mixing and going-off means that ready-mix should
be placed within 10 minutes of batching at the plant.
• Modern additives modify precisely that time span however, the amount of additive added
to the mix is very important.