2. Introduction
• The idea of Ready-Mix Concrete (RMC) was
initially introduced by the designer Jurgen
Magens, he got his patent of RMC in Germany
in 1903.
• Ready-mix concrete (RMC) is a ready-to-use
material, with adjusted mixture of cement, sand,
aggregates and water.
• Ready mix concrete is a sort of concrete that is
produced in a cement manufacturing plant, or
specifically referred to as batching plant,
consistent with a given set of proportions, then
delivered to worksite, by truck mounted with
mixers.
• This ends up in a certain mixture, permitting
specialty concrete mixtures to be developed and
enforced on construction sites.
3. Materials Required for RMC
• Aggregates: They provide body to the concrete, bring down shrinkage and
impact economy. The mere fact that the aggregates occupy 60-75% of the
quantity of concrete. Aggregates are divided into 2 classes from the
consideration of size: Coarse aggregate and Fine aggregate
Coarse aggregate Fine aggregate
4. • Fly Ash: Fly Ash is a by-product from
coal-fired electricity generating power
plants. Fly Ash particles give a larger
workability of the powder portion of the
concrete mixture which ends up in larger
workability of the concrete and a lowering
of water demand for identical concrete
consistency.
Materials Required for RMC
• Cement: Cement is a binder material that sets
and hardens separately and may bind
different materials with each other. It’s a dry
powder that reacts with chemicals and with
water to bind the particles of mixture,
forming concrete. Portland cement is often
employed in concrete production.
5. Materials Required for RMC
• Admixture/Additive: Admixtures are solid or
liquid chemical substances that may be added to
RMC before or throughout preparation. example:
Retarding admixtures (mainly employed in hot
weather to retard the reaction of hydration)
• Water: The amount of water in concrete controls recent and
hardened properties of concrete as well as workability,
compressive strength, permeability, durability and shrinkage.
For these reasons, limiting and managing the quantity of water
in concrete is vital for each constructability and service life.
6. Methods for producing RMC
• Transit or truck mixing
The dry materials are proportioned at
the RMC plant, the water being used,
and the mixing done en route to the
job in a truck mixer, which essentially
consists of a mixer drum mounted on a
conventional chassis
7. Methods for
producing RMC
• Central mixing:
In central mixing, both the
operations of proportioning and
mixing are carried out by the
batching plant and deliver the
mixed concrete to the site in an
agitator truck, which keeps the
mix concrete in correct form.
8. Methods for
producing RMC
• Shrinkage mix:
Concrete that is partially mixed in
a plant mixer and then discharged
into the drum of the truck mixer
for completion of the mixing is
called shrink mixed concrete.
9. Ready Mix
Concrete Plant:
A ready-mix concrete plant is a
permanent installation with mechanical
handling for the storage, proportioning
and mixing of materials. The location,
size of the plant and layout are
governed by several considerations,
depending upon local conditions
which require careful study before the
design and construction of the plant
are undertaken.
10. Location Size Layout
In the operation of a RMC
concern, the
transportation of the
concrete to the site of the
job is generally one of the
most expensive items and
the RMC plant should, as
far as possible, be situated
in the center of the market
The size of plant will
depend chiefly on the
potential demand for
which the plant has to
cater. This in turn is
dependent upon the
quality of concrete
construction carried out in
a town or city.
The plant layout should be
so arranged that it satisfies
the following considerations.
Firstly, it ensures the
maximum efficiency in
operation. Secondly, it
provides adequate space for
the storage of materials and
thirdly, it does not hamper
future expansion.
Ready Mix Concrete Plant:
11. While ready mixed concrete can be delivered to
the point of placement most of it is brought to
the construction site in truck-mounted, rotating
drum mixers. Truck mixers have a revolving
drum with the axis inclined to the horizontal.
Delivery of RMC
Inside the shell of the mixer drum
are a pair of blades or fins that
wrap in a helical (spiral)
configuration from the head to the
opening of the drum. The concrete
is loaded and mixed, it is normally
hauled to the job site with the drum
turning at a speed of less than 2
rpm.
12. • 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 in areas zoned for industrial use, and
yet the delivery trucks can service residential districts
or inner cities.
• Better quality concrete is produced. Site Mix can
produce higher compression strength with less water
than standard batching methods.
MERITS OF RMC
• 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 washout. 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.
13. • 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 must be able to carry
the weight of the truck and load. Concrete is
approx. 2.5tonne per m’.
• This problem can be overcome by utilizing so-
called 'minimix' companies, using smaller 4m
capacity mixers able to access more restricted sites.
DEMERITS OF RMC
• 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.
14. Tests On Fine Aggregates:
• Sieve Analysis
• Specific Gravity
• Bulk Density (Loose / Rodded)
• Silt Test by Volume / Weight
• Water Absorption
Tests Carried On RMC (At Factory)
Tests On Coarse Aggregates:
• Sieve Analysis
• Specific Gravity
• Aggregate Impact Value
• Bulk Density (Loose / Rodded)
• Water Absorption
• Crushing Test
15. Tests On Water:
• pH Value
• Chloride
• Sulphit
• Nitrite
Tests Carried On RMC (At Factory)
Tests On Fresh Concrete:
• Workability
• Setting time
• Unit weight
• Air content
16. The Slump Test to Ensure Ready
Mix Concrete Quality
Slump test is one of the most important
tests to ensure the reliability, durability and
consistency of freshly made concrete in a
ready-mix concrete factory .Therefore, the
slump test is executed to check that a
ready-mixed concrete is workable.
Tests Carried On RMC (At Site)
Compressive Strength Test of Concrete
Based on this test, one can either accept or reject a concrete
work. Compressive strength as a concrete property depends
on several factors related to quality of used materials, mix
design and quality control during concrete production.
Depending on the applied code, the test sample may be
cylinder [15 cm x 30 cm is common] or cube [15 cm x 15cm
x 15 cm is the most common]
17. During Slump Test
• ASTM C 94, "Standard
Specification for Ready Mixed
Concrete," states: "If the measured
slump or air content falls outside
the specified limits, a check test
shall be made immediately on
another portion of the same
sample. In the event of a second
failure, the concrete shall be
considered to have failed the
requirements of the specification.
When to accept the batch and when to reject it
Duo The Condition of Concrete
a) If the concrete mixture is too wet,
coarse aggregates settle at the bottom
of concrete mass and as a result
concrete becomes non-uniform
composition,
b) If the concrete mixture is too dry, it
will be difficult to handle and place it
in position.
18. Conclusion
Ready Mix Concrete plant is a modern technique
of production of concrete in large quantities
away from the actual site of placing. It is very
useful in cities where demand of concrete is very
high and construction sites are in congested
areas where mixing on site is not possible. It is
suitable for projects like Dam, Roads, Bridges,
commercial complex, Malls and all types of mass
construction where time limit plays a vital role
and where demand is huge.
