Ready Mix ConcreteReady Mix ConcreteByBy

ErEr.N..N.KalidossKalidoss, B.Tech.,, B.Tech.,

Ready Mix ConcreteReady Mix Concrete

�� A concrete whose constituents are weigh batched at a A concrete whose constituents are weigh batched at a central batching plant, mixed either at the plant itself central batching plant, mixed either at the plant itself or in truck mixers, and then transported to the or in truck mixers, and then transported to the construction site and delivered in a condition ready to construction site and delivered in a condition ready to use, is termed as READY MIXED use, is termed as READY MIXED CONCRETE(RMC)CONCRETE(RMC)

�� Enables the places of manufacture and use of concrete Enables the places of manufacture and use of concrete being separated and linked by suitable transport being separated and linked by suitable transport

operationoperation..

ApplicationsApplications

�� This technique is useful in congested site or This technique is useful in congested site or

diverse work Places and saves the consumer diverse work Places and saves the consumer

from the botheration of procurement, storage from the botheration of procurement, storage

and handling of concrete materials and handling of concrete materials

�� Ready mix concrete is produced under factory Ready mix concrete is produced under factory

conditions and permits a close control of all conditions and permits a close control of all

operations of manufacture and transportation of operations of manufacture and transportation of

fresh concretefresh concrete

SPECIFICATIONS SPECIFICATIONS

Quality of ready mix concrete is generally Quality of ready mix concrete is generally

specified in terms of two systemsspecified in terms of two systems

�� Performance parametersPerformance parameters

�� Prescriptive specificationPrescriptive specification

Performance parameters Performance parameters

�� It is the best way to order ready mixed concrete It is the best way to order ready mixed concrete

because RMC producer, who is expert in the because RMC producer, who is expert in the

field, would design an economical mix with the field, would design an economical mix with the

desired propertiesdesired properties

�� The RMC producer accepts the responsibility for The RMC producer accepts the responsibility for

the design of the mixture for the desired the design of the mixture for the desired

performanceperformance

Perspective Specifications Perspective Specifications

�� Purchaser specifies aggregate size, slump, Purchaser specifies aggregate size, slump, air content, cement content, or weight of air content, cement content, or weight of cement per cubic meter of concrete, cement per cubic meter of concrete, maximum water content and admixtures maximum water content and admixtures requiredrequired. .

�� The purchaser accepts the responsibility The purchaser accepts the responsibility for concrete strength and its performance. for concrete strength and its performance.

ORDERING OF CONCRETEORDERING OF CONCRETE

�� RMC is ordered and supplied by volume RMC is ordered and supplied by volume (cum) in a freshly mixed and unhardened (cum) in a freshly mixed and unhardened state state

�� When ordering concrete, 5 to 10 percent When ordering concrete, 5 to 10 percent more concrete than estimated from a more concrete than estimated from a volumetric calculation is orderedvolumetric calculation is ordered

�� This will account for the wastage, over This will account for the wastage, over excavation, spreading of forms, some of excavation, spreading of forms, some of loss of entrained air, settlement of wet loss of entrained air, settlement of wet mixture and change in volumemixture and change in volume

PROPORTIONING OF RMC PROPORTIONING OF RMC

�� The proportioning of an RMC aims at The proportioning of an RMC aims at obtaining the properties, such as obtaining the properties, such as workability, strength, durability and workability, strength, durability and appearance appearance

The following basics of a good concrete mix should The following basics of a good concrete mix should

be considered while proportioning RMCbe considered while proportioning RMC

�� Concrete aggregates should be clean, Concrete aggregates should be clean, strong and durable. strong and durable.

PROPORTIONING OF RMC PROPORTIONING OF RMC

�� Fly ash or other supplementary Fly ash or other supplementary cementitiouscementitious materials added to materials added to RMC, which enhance concrete RMC, which enhance concrete properties properties

�� Admixtures are commonly used to Admixtures are commonly used to improve the rate of setting and improve the rate of setting and strength of development of concrete strength of development of concrete

Production of RMC Production of RMC

There are three principal categories of RMC There are three principal categories of RMC

�� Transit Mixed Concrete Transit Mixed Concrete

�� Shrink Mixed ConcreteShrink Mixed Concrete

�� Central mixed concrete Central mixed concrete

TRANSIT MIXED CONCRETE TRANSIT MIXED CONCRETE

�� It is also called truck mixed or dry batched It is also called truck mixed or dry batched concrete concrete

�� All the ingredients are charged directly in All the ingredients are charged directly in the truck mixer .the truck mixer .

�� Most of the water usually batched at the Most of the water usually batched at the plantplant

TRANSIT MIXED CONCRETE TRANSIT MIXED CONCRETE

There are three options for truck mixed There are three options for truck mixed concreteconcrete

�� Concrete mixed at the job site:Concrete mixed at the job site:

�� Concrete mixed in the yard or central Concrete mixed in the yard or central batching plant batching plant

�� Concrete mixed in transit:Concrete mixed in transit:

TRANSIT MIXED CONCRETE TRANSIT MIXED CONCRETE

Concrete mixed at the job site:Concrete mixed at the job site:

�� While traveling to the job site the drum is While traveling to the job site the drum is turned at agitating speed (slow speed).turned at agitating speed (slow speed).

�� After arriving at the job site, the concrete After arriving at the job site, the concrete is completely mixed. The drum is then is completely mixed. The drum is then turned for 70 to 100 revolutions, or about turned for 70 to 100 revolutions, or about 5 minutes, at mixing speed.5 minutes, at mixing speed.

TRANSIT MIXED CONCRETE TRANSIT MIXED CONCRETE

Concrete mixed in the yard or central Concrete mixed in the yard or central batching plantbatching plant

�� The drum is turned at high speed or 12The drum is turned at high speed or 12--15 15 rpm for 50 revolutions. rpm for 50 revolutions.

�� This allows quick check of batch. The This allows quick check of batch. The concrete is then agitated slowly while concrete is then agitated slowly while driving to the job site driving to the job site

TRANSIT MIXED CONCRETE TRANSIT MIXED CONCRETE

Concrete mixed in transit:Concrete mixed in transit:

�� The drum is turned at medium speed The drum is turned at medium speed

or about 8 rpm for 70 revolutions or about 8 rpm for 70 revolutions

while driving to the job site. .while driving to the job site. .

SHRINK SHRINK -- MIXED CONCRETE MIXED CONCRETE

�� Concrete that is partially mixed in a stationary Concrete that is partially mixed in a stationary plant mounted mixer and then discharged into plant mounted mixer and then discharged into the drum of truck mixer for completion of the drum of truck mixer for completion of mixingmixing feelingfeeling

CENTRALCENTRAL-- MIXED MIXED CONCRETE CONCRETE

�� Central mixed concrete batch plants include a Central mixed concrete batch plants include a stationary, plant mounted mixer that mixes the stationary, plant mounted mixer that mixes the concrete before it is discharged into a truck mixerconcrete before it is discharged into a truck mixer

�� TypesTypes--Tilt drum mixer, horizontal shaft paddle mixer, Tilt drum mixer, horizontal shaft paddle mixer, pan mixer, and slurry mixer. pan mixer, and slurry mixer.

MIX MOBILESMIX MOBILES

�� MixMix -- mobile plants or plantsmobile plants or plants--on wheels are truck on wheels are truck mounted, volumetric batching and continuous mixing mounted, volumetric batching and continuous mixing units which often supply small volume or specialty units which often supply small volume or specialty pourspours

�� Offer the convenience of freshly mixed concrete in Offer the convenience of freshly mixed concrete in fairly précised quantities. fairly précised quantities.

DELIVERY OF RMCDELIVERY OF RMC

•• Ready mix concrete can be delivered to the Ready mix concrete can be delivered to the construction site in truckconstruction site in truck-- mounted, rotating mounted, rotating drum mixersdrum mixers..

•• Truck mixers have a revolving drum with the Truck mixers have a revolving drum with the axis inclined to horizontalaxis inclined to horizontal..

•• To load or charge the raw materials from a To load or charge the raw materials from a transit mixed plant or central mixed plant into transit mixed plant or central mixed plant into the truck, the drum must be turned very fast in the truck, the drum must be turned very fast in the changing direction.the changing direction.

DELIVERY OF RMCDELIVERY OF RMC

•• After the concrete is loaded and mixed, it After the concrete is loaded and mixed, it

is normally hauled to the job site with the is normally hauled to the job site with the

drum turning at the speed of less than 2 drum turning at the speed of less than 2

rpm. .rpm. .

•• The truck mixer having front discharge The truck mixer having front discharge

units are more popular than the traditional units are more popular than the traditional

one having rear discharge unitsone having rear discharge units

INSPECTION AND TESTINGINSPECTION AND TESTING

•• Since RMC is a manufactured product, specific Since RMC is a manufactured product, specific

control tests and evaluations are required during control tests and evaluations are required during

the manufacturing process to produce the manufacturing process to produce

predictable high quality concretepredictable high quality concrete

•• Some of the important properties of concrete Some of the important properties of concrete

that are measured by basic quality control tests that are measured by basic quality control tests

are strength,temperature,slump, air content, are strength,temperature,slump, air content,

and unit weightand unit weight

INSPECTION AND TESTINGINSPECTION AND TESTING

•• Concrete producer to agree to supply Concrete producer to agree to supply

concrete in accordance with relevant concrete in accordance with relevant

national codes. national codes.

•• Any agreement between the producer and Any agreement between the producer and

a purchaser should include definition of a purchaser should include definition of

the basis of purchase.the basis of purchase.

THANK YOUTHANK YOU