KAS-2012 1

TRANSPORTATION OF CONCRETE

K A Shah

B.Sc.(Civil Engg.) MSc.(Environment Engg.)

Ex-GM-MNC

Guest Faculty- CTE

KAS-2012 2

TRANSPORTATION OF CONCRETE

Precaution in concrete transportation: Homogeneity of conc. Mass is maintained Movement of hand trolly or truck on rough

road surface makes vibrations This results in deposition of heavy

aggregates at bottom of truck Water & cement slurry comes on top.

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METHODS OF TRANSPORTATION

1. Mortar Pan2. Wheel barrow3. Truck Mixer & dumpers4. Crane, Bucket & rope way5. Belt conveyors6. Chutes7. Skip & hoist8. Transit Mixer9. Pump & pipeline10. Helicopter

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MORTAR PAN

Common method in India More labour required Segregation of concrete is less Greater surface area of concrete is

exposed to sun, concrete dries.

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WHEEL BARROW

When transportation of concrete is at

ground level. Movement of wheel on rough road

surface, segregates concrete. Some wheel barrows have pneumatic

wheel to reduce vibration

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CRANE

Used for transporting concrete above ground level.

For high rise buildings. Cranes are fast Can move horizontally & vertically Concrete in skip discharge from bottom In bucket concrete is discharged by tilting.

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CONCRETE TRANSPORT BY CRANE-VIDEO

Pouring Concrete-Cement Truck-Crane-Construction Excavation Site.flv

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BUCKET & ROPEWAY

Use for construction in: Valley Bridge pier in river Dam

Advantage:

Concrete is not exposed to sun or air & no loss of water.

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ROPEWAY-VIDEO

Package

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Truck Mixer & dumpers

Used for large concrete works. Can travel any part of site. Dumpers - 2-3 M3 Capacity Trucks – 4 M3 Capacity Bottom surface of truck is kept wet Top of truck is covered to prevent

evaporation

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BELT CONVEYOR-VIDEO

Package

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BELT CONVEYORS

Limited use in construction

Advantages:

Can transport large volume Very quick Can go where access is limited

Disadvantages :

On steep slope concrete segregates. Exposed to sun for long time.

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CHUTE

For transporting from ground level to lower level. (basement etc).

Used where labour can not reach due to less space in trench etc.

Made of metal Slope should not be < 1 vertical : 2.5

horizontal.

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SKIP & HOIST -VIDEO

Package

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SKIP & HOIST

Labour can go upto 3rd or 4th floors. So skip is used for transport vertically up

(in multistory building). Skip travels on vertical rail. Skip can discharge manually or

automatically.

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TRANSIT MIXER

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TRANSIT MIXER

Used for long distance travel in RMC plant. Concrete is continuously agitated in truck drum

(2 – 6 rpm). Also transported mix in dry condition and water

is added on reaching the destination. Wet Mix in truck must reach site in 1- 1.5 hours. Pumps are also fitted on truck mixer to

discharge concrete.

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PUMPS & PIPELINE

Most popular method Reliable & good quality pumps are used. Mostly operated by diesel. Concrete is placed in collecting hopper. Rotating blades in hopper pushes concrete

towards pipe. Vacume in hose pipe (600 mm Hg) Rotating rollers in pump chambers squeeze the

concrete in pipe and flow of concrete is started. Concrete is discharged from other end of hose

pipe. Concrete can be pumped upto 400 m height and

2000 m distance.

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SECTION OF PUMP

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PIPELINE

Pipeline should : Have correct diameter as per pump

pressure. (generally 125 mm) Have sufficient thickness Good couplings Poor pipeline can cause blockage.

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PIPELINE

Thumb rule : For 30 M3 /hr concrete and 200 m length, dia should be 100 mm.

Length > 500 m then dia = 150 mm. Dia = 3 to 4 times the size of aggregate Leaky pipe & coupling result in escape of

water /air & finally block the concrete. Vertical pipe should good otherwise

difficult to change at height. Pump is kept at distance from building

about 15 % of vertical length.

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CONCRETE FLOW IN PIPE

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PUMPABLE CONCRETE

Concrete which can be pushed through a pipeline is called pumpable concrete.

Friction between pipe wall and concrete is less. Concrete flows in the form of plug which is separated

from pipe wall by a thin layer of lubricating cement paste. Flow resistant must be < pump pressure. If the concrete is more wet then water comes out of mix

which makes more resistance to flow. Stiff and also very wet concrete is not pumpable.

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Design of pumpable concrete

Concrete Mix is so designed that all material remain together.

Mix must make redial movement of grout to maintain lubricating paste.

Mix should be deformed at bends Cement & fine particles (0.25 mm size) are important for

good flow. 350 to 400 Kg/ M3 of fine particles are necessary for flow. Slump of pumpable concrete is above 75 mm.

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PROBLEMS IN PUMPING

Blockage in pipe Pipe should be cleaned after each day

operation Blockage can be cleaned by forward-backward

pumping. Tapping pipe with hammer Clean pipe with rod or sponge ball pushed by

compressed air.

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THANKS