READY MIX CONCRETE

1. A POWERPOINT PRESENTAION
ON READY-MIX CONCRETE

2. • RMC IN INDIA:
In India RMC was first initially was used in
1950 during the construction sites of Dams
like Bhakra Nangal, Koyna. At the
construction the transportation of concrete
is done by either manually or mechanically
using ropeways & buckets or conveyor
systems.

3. • General introduction:
• Ready Mix Concrete (RMC) is a specialized material in
which the cement aggregates and other ingredients are
weigh-batched at
• a plant in a central mixer or truck mixer, before delivery to
the construction site in a condition ready for placing by the
builder. Thus, `fresh' concrete is manufactured in a plant
away from the construction site and transported within the
requisite journey time. The RMC supplier provides two
services, firstly one of processing the materials for making
fresh concrete and secondly, of transporting a product within
a short time

4. • ADVANTAGES
• A centralized concrete batching plant can serve a wide area.
• The plants are located in areas zoned for industrial use, and
yet the delivery trucks can service residential districts or inner
cities.
• Better quality concrete is produced.
• Elimination of storage space for basic materials at site.
• Elimination of hiring of plant and machinery.
• Wastage of basic materials is avoided.
• Labors associated with production of concrete is eliminated.
• Time required is greatly reduced.
• Noise and dust pollution at site is reduced.

5. • ADVANTAGE OF RMC
• 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 labor, 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

6. • DISADVANTAGES:-
• The materials are batched at a central plant, and the
mixing begins at that plant, so the traveling time from
the plant to site is critical over longer distances.
• Access roads, and site access have to be able to carry
the weight of the truck and load concrete is approx
2.5tonne per comm.
• concrete’s limited time span between mixing and
going-off means that ready-mix should be placed
within 2hours of batching at the plant

7. • 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. (Green concrete is approx. 2.5 tone 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.[2] Modern admixtures can modify that time span precisely,
however, so the amount and type of admixture added to the mix is
very important.

8. • Standard ready-mix concrete vs. site-
mix
• concrete 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
than standard batching methods.

9. • MIXING PROCESS:
• Thorough mixing of the materials is essential for the
production of uniform concrete. The mixing should
ensure that the mass becomes homogeneous,
uniform in color and consistency. There are three
methods adopted for mixing Ready Mix Concrete.
• Following are the three types of mixing process of
RMC
• 1. Transit Mixed (or "truck-mixed") Concrete
• 2. Shrink Mixed Concrete
• 3. Central Mixed Concrete

10. • TRANSIT MIXING:-
• It is delivered to the worksite, often in transit mixers capable of mixing
the ingredients of the concrete just before the delivery of 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.
• CENTRALLY MIX:-
• 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. However, in the case of the
truck-mixed concrete, the batched materials (sand, gravel and cement)
are carried and water is added just at the time of mixing. In this case
the cement remains in contact with the wet or moist material and this
phase cannot exceed the permissible period, which is normally 90
minutes.
• 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.

11. • Transit Mixed (or "truck-mixed") Concrete:-
• In transit-mixed concrete, also called truck mixed or dry-
batched, all of the raw ingredients are charged directly in the
truck mixer. Most or all water is usually batched at the plant.
• Concrete mixed at the job site:- While traveling to the job
site the drum is turned at agitating speed (slow speed). After
arriving at the job site, the concrete is completely mixed.
• Concrete mixed in the yard:- The drum is turned at high
speed or 12-15 rpm for 50 revolutions. This allows a quick
check of the batch. The concrete is then agitated slowly while
driving to the job site.
• Concrete mixed in transit:- The drum is turned at medium
speed or about 8 rpm for 70 revolutions while driving to the
job site. The drum is then slowed to agitating speed.

12. • Time in Transport:
• The general requirement is that concrete shall be
discharged from the truck mixer within 2 hours of the
• time of loading. However, longer period may be
permitted if retarding admixtures are used or in cool
• humid weather or when chilled concrete is produced
SAMPLING AND TESTING OF READY-
MIXED CONCRETE (As per IS 4926-
2003):
For the assessment of compliance of ready-mixed concrete, the point and the
time of sampling shall be
at the discharge from the producer’s delivery vehicle or from the mixer to the
site or when delivered
into the purchaser’s vehicle.

14. Volumetric concrete mixer
• As an alternative to ready-mix concrete, volumetric
mobile mixers may be used to provide metered
concrete services. 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. This is a hybrid approach between ready-
mix concrete and traditional on-site mixing.[3]

15. • A volumetric concrete mixer (also known as volumetric mobile
mixer and metered concrete truck) 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.[1]
• The mixer is a mixing device that measures the raw materials
using volume rather than weight. The volumetric mixer blends
the concrete mixture using an auger or a paddle or a drum
device to mix the ingredients with water. The volumetric
mixing process starts with a batch metering system that
allows the volume of raw materials to be measured prior to
entering the mixing chamber. This process can be as simple
as using a measured bucket, to highly sophisticated and
computerized batch plants that feed the correct volume.[2]

16. • 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
than standard batching methods.

18. • Table 1 Assumed Standard Deviation
• Grade of Concrete Assumed Standard
Deviation N/sq.mm
• M 10 3.5
• M 15
• M 20 4.0
• M 25
• M 30 5.0
• M 35
• M 40
• M 45
• M 50

19. • ADMIXTURE:
• A substance added to the basic concrete mixture to alter one or more
properties of the concrete; i.e. fibrous materials for reinforcing, water
repellent treatments, and coloring compounds.
• Air-entraining admixtures (mainly used in concrete exposed to freezing
and thawing cycles)
• Water-reducing admixtures, plasticizers (reduce the dosage of water
while maintaining the workability)
• Retarding admixtures (mainly used in hot weather to retard the reaction
of hydration)
• Accelerating admixtures (mainly used in cold weather to accelerate the
reaction of hydration)
• Super plasticizer or high range water-reducer (significantly reduce the
dosage of water while maintaining the workability)
• Miscellaneous admixtures such as corrosion inhibiting, shrinkage
reducing, coloring, pumping etc.

22. BATCHING PLANT

23. THANK YOU
• SANTANU MAHATO(52702)
• SOURAV CHANDRA MAHATO(52718)
• SOUMEN PATRA(52716)
• SOUMYADIP SAMANTA(52717)
• RAKHAL MAHATHA(52695)