pumped conc practice - copy

7/29/2019 Pumped Conc Practice - Copy

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Pumped Concrete Practice


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Guidance Notes - Concrete Mix

Concrete which can be pushed thro a pipeline

is called a pump able concrete

A normal concrete with increased fines content

Does not require any additional Cement

Control of workability of prime importance;

Slump range- 90 to 120 mm; individual slumpmeasurements may vary by 25 mm

Desired slump achieved by choosing proper

quality / dosage of super-plasticizer


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Concrete Mix Quality of Sand

Control of quality of sand very vital; sand

conforming to zone 1,2,3 or 4 may be used

There should be no silt content; wash the sand

thoroughly to remove all the silt

Depending upon the coarseness or fineness of

the sand, the sand content should be adjusted

based on trial mixes. Course aggregate shaped

should be cubical or spherical; river gravel

(shingle) gives the best result for pumping


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Sand Content

Pumpable concrete must slide along the wall of

the pipeline and be able to move thro the

bends

Cement and finer particles of sand acts as a

lubricant when the concrete passes thro the

pipeline. The contents of fines( Cement + Fine

Sand) should be 450 Kg/ cum Concrete with 20mm aggregates, or 400 Kg/cum with 40 mm

aggregates


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Influence of size, shape of Aggregates

Flaky, Longitudinal shapes have more surface

area than rounded; for flaky / crushed stones,

sand content increased by 10%; stone dust or

fillers are suitable to increase the sand content

The surface of aggregates may be very smooth

(as in the case of river gravel) or rough or sharp

edged ( Crushed material ); for flaky or sharpedged or crushed aggregates; the quantity of

fines should be increased by about 10%


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Priming of Dry Pipelines

Before starting pumping, the dry pipeline is

primed ( buttered ) using cement- water mix

Follow manufacturers recommendation as to

amount of cement to be used

Lubricating mix is charged in to the hopper with

pump switched off and pushed in to the pipeline

before the first regular concrete mix is pumped.This is done first before starting concrete

pumping; repeated if pumping is interrupted


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Priming of Dry Pipelines

Minimum quantity of lubricating mix :

- 50Kg of cement and water adequate for truck

mounted concrete pumps with placing booms

up to vertical reached of 25 m- 100 Kg of cement in water for larger reaches

For pipelines more than 50 m long, lubricating

mix is made of 2 parts of cement and 1 partsand and water


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Quantities of lubricating mixes-125mm dia

Length (m) Lubricating

Mix- Liter

Cement

(Kg)

Sand (Kg)

50 200 200 100

100 300 300 150

200 500 500 250

300 750 750 350

400 1000 1000 500

600 1500 1500 750


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Use of Fly ash/ Slag

For effective pumping minimum quantity of finematerials (cement, fly ash or slag+ fine fractionof sand passing thro 300) is required, usually

450 Kg/cum of concrete- about 450 KgFly ash or slag is necessary to get continuousgrading of fine materials including cement in theconcrete mix; for example:

cement: 250 Kg

fly ash: 80 Kg

fine sand: 120 Kg, total 450 Kg is ok


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Minimum cement content

Minimum cement content for pumped concreteis same as for normal concrete

Cement content includes cement + mineral

admixtures such as fly ash/ slagMinimum cement content is specified fordifferent environmental conditions:

Mild, Moderate- 300 Kg/ cum

Severe- 320 Kg/cumVery Severe- 340 Kg/cum


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Pipeline

3 dia are in normal use 100mm 125m 150mm

125mm most widely used

Choice of pipeline diameter depends on maxsize of coarse aggregate

- 125mm ID pipeline ok for 40mm aggregates

- 100mm used for 20mm aggregates

- 150mm used for larger size aggregate

100mm pipeline can be used for concrete with

20mm aggregates provided there is no oversize


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Pipeline Layout , Cleaning

Lay in one straight line, avoid / minimize bends

Lay vertically or horizontally; avoid inclined line

On completion of pumping activity the pipelinesare cleaned using a rubber ball and water under

pressure; the ball may also be pushed by

compressed air

A properly cleaned pipeline is necessary for

trouble free pumping; concrete and mortar

residues in the pipeline may clog concrete flow


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Distribution of Concrete

When using concrete pumps cost effective

distribution of concrete should be considered

Truck mounted concrete pumps achieve high

outputs because they place concrete exactly

where it is needed

Concrete is produced in a batching plant,

transported by truck mixers and fed to the pump

Pump can also be placed directly below the

batching plant, avoiding truck mixers


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Distribution of Concrete

Concrete can also distributed in an economical

manner by placing the concrete with stationary

concrete pumps in combination with secrete

placing booms

Horiz reach of separate placing booms range

from 20m to 50m; installed in the building to

enable coverage within the whole workingrange


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Separate Placing Booms

The placing booms are easily repositioned by

Tower cranes to cover large areas

Tubular columns for mounting the placing

booms equipped with quick connections; a

climbing device for climbing inside the building

Placer booms of more than 30m reach are

mounted on Tower crane masts

For larger buildings, many placer booms used,

each fed by a concrete pump


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Concrete distribution with end hose

A 3m long flexible end hose used for

distribution of concrete

2 additional men are required

The use of a chute, a circular distributor or a

combination of both instead of an end hose

should be preferred

For vertical placing, there must be a starting

distance between the concrete pump and the

vertical pipeline, atleast 10% of vertical distance


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Pumping Heights

Pumping height depends on the maximum

placing pressure of the concrete pump;

pumping heights of 700m have been achieved

for the construction of Burj Dubai Building

Horizontal placing distance of > 1200m has

been achieved in some Hydel Projects in India

With descending pipelines, ensure conc does

not break and segregate in the descending line;

install shut off wall after the descending line


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Blockages

Generally attributed to human failure

Blockages indicated by a rapid rise in pressure

Prevent foreign matter in the pipeline by using agrill in the charging hopper

Bleeding concrete; increase the fines

Inadequate mixing timeUnpumpable concrete, too thin consistencies,

long pumping interruptions, changes in conc

consistencies

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