(Pumping & Placing) B. Bhattacharjee CIVIL …web.iitd.ac.in/~bishwa/LEC_PDF_774/LEC5.pdf · Concrete: Production (Pumping & Placing) B. Bhattacharjee CIVIL ENGINEERING DEPARTMENT

1DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI

CEL 774 CONSTRUCTION PRACTISES

Concrete: Production (Pumping & Placing)B. Bhattacharjee

CIVIL ENGINEERING DEPARTMENTIIT DELHI

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General OutlineGeneral Outline

Concrete Production.Concrete Production.PumpingPumpingPlacingPlacing

B. Bhattacharjee

DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI

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Pumping of ConcretePumping of Concrete

B. Bhattacharjee


–– Pumping is used for both transporting Pumping is used for both transporting and placing of concrete.and placing of concrete.

–– Combines both vertical and horizontal Combines both vertical and horizontal transport in one. transport in one.

–– it can place concrete in congested it can place concrete in congested sites with little access otherwisesites with little access otherwise ..

–– Small or large quantities of concrete Small or large quantities of concrete can be placed in the form, can be placed in the form, continuously at a very fast rate. continuously at a very fast rate.

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Pumping of ConcretePumping of Concrete

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–– Pumping of concrete requires use of Pumping of concrete requires use of mix having special properties suited to mix having special properties suited to pumping itself.pumping itself.

–– Pumping rates ranges from 10 to 75 Pumping rates ranges from 10 to 75 cubic meter/hourcubic meter/hour ..

–– Concrete can be pumped to a distance Concrete can be pumped to a distance of 90of 90--300 m horizontally.300 m horizontally.

–– Concrete can be pumped from 30 to 90 Concrete can be pumped from 30 to 90 m vertically. m vertically.

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Types of PumpTypes of Pump

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–– Piston Pumps.Piston Pumps.– Mechanical– Hydraulic Pumps.

–– Peristaltic Pumps/ SqueezePeristaltic Pumps/ Squeeze--cretecretePumpsPumps..

–– Mobile boom pumps.Mobile boom pumps.–– Trailer Pumps.Trailer Pumps.–– Pneumatic Placers Pneumatic Placers

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– Mobile Boom Pump

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Pneumatic PlacerPneumatic Placer

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– A: Casing

– B: Inlet Hopper

– C: Bell shaped inlet

– D: Air entry pipe and nozzle.

– E: Nozzle

– F: Delivery

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Rheology of Fresh Concrete Rheology of Fresh Concrete

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–– For solids Shear For solids Shear ττ = G= Gγγ–– Liquid deforms continuously under Liquid deforms continuously under

shear stress no matter how small the shear stress no matter how small the stress is.stress is.

–– For liquids For liquids ττ = = μμ ((ddγγ/dt/dt)) ..–– NewtonNewton’’s law for viscous fluid is s law for viscous fluid is ττ = = μμ ((dv/dydv/dy) ) same as abovesame as above..

–– Concrete/cement paste can stand on a Concrete/cement paste can stand on a pile suggests that some shear stress is pile suggests that some shear stress is necessary for flow to occur. necessary for flow to occur.

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Rheology of Fresh Concrete Rheology of Fresh Concrete

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Rheology of Fresh Paste Rheology of Fresh Paste

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VICAT’s Type apparatus is usedf is the yield shear stressP load on the penetrating rodg acceleration due to gravityR radius of penetrating rodH is the depth of penetration

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Rheology of Fresh Paste Rheology of Fresh Paste

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η is viscosity in CPη0 is viscosity of waterδ is a parameter representing

distance between particle in micron

η = [(0.5 s1/3 )/(w/c-{w/c}n )]-1b is an experimental factor w/c is the water to cement ratio and subscript “ n” represent that for normal consistency s is Blain’s fineness in cm2/g.

η = 1.3 δ -0.6-1

η = η0 e-b(w/c)

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Workability of Fresh Concrete Workability of Fresh Concrete

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––Three componentsThree components–– A. Compactibility i.e. function of the A. Compactibility i.e. function of the

work done work done ½½((ττ00+ + μμ σσ) ) γγ y y ..–– B. Mobility i.e. function of ( B. Mobility i.e. function of ( μμ, , ττ00 and and

m.s.am.s.a. D ). D )–– C. Stability i.e., function of tensile C. Stability i.e., function of tensile

strengthstrength

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Concrete Flow Concrete Flow

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–– Flows in form of plug separated from Flows in form of plug separated from pipe wall by a layer of lubricating later.pipe wall by a layer of lubricating later.

–– No relative velocity between aggregate No relative velocity between aggregate particle for a straight pipe of constant particle for a straight pipe of constant crosscross--sectionsection..

–– Lubricating layer near pipe boundary is Lubricating layer near pipe boundary is essential for pumpability.essential for pumpability.

–– Compacting effect of pressure Compacting effect of pressure consolidates and forces grout out consolidates and forces grout out

–– TrowellingTrowelling effect due to frictional drag effect due to frictional drag at boundary pulls grout outat boundary pulls grout out

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Concrete FlowConcrete Flow

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Concrete Flow Concrete Flow

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–– When mortar which has enough water When mortar which has enough water and is sufficient to fill in all the voids in and is sufficient to fill in all the voids in aggregate and is more to create aggregate and is more to create lubricating layer it is said to be lubricating layer it is said to be SATURATEDSATURATED..

–– In Saturated concrete radial and axial In Saturated concrete radial and axial pressures are same and fine content is pressures are same and fine content is important. important.

–– Too much cohesiveness due to excess Too much cohesiveness due to excess cement and fines may prevent cement and fines may prevent formation of lubricating layerformation of lubricating layer

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PumpabilityPumpability

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Saturated

Transition

Unsaturated

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– Fines must be sufficient to resist passageof water i.e., blocked filter effect.

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i0 D

Rx4pp −=

– p = pressure at a distance x– p0= pressure at the delivery end of pump.– R= flow resistance /area of pipe– Di= Internal diameter of pipe

– EQUATION FOR SATURATED CONCRETE

R4Dpx i0

max =

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k

Ae1epp

i

i

Dxk4

Dxk4

0 μ

⎟⎟⎠

⎞⎜⎜⎝

⎛−

−=

μ

μ−

– μ = coefficient of friction between concrete and pipe wall

– A= adhesive resistance, similar to yield stress .– k= radial to axial pressure ratio

– EQUATION FOR UNSATURATED CONCRETE

AkpAln

k4Dx

0

imax +μμ

−=

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– PRESSURE BLEED TEST

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Effect of Pumping on concreteEffect of Pumping on concrete

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– Drier consistency

– Increase In Temperature

– Slight increase in air content

– No change in strength or shrinkage, although aluminum pipes may cause loss of strength

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Dos & Dos & DonDon’’ts in ts in concrete concrete HandlingHandling

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(Pumping & Placing) B. Bhattacharjee CIVIL …web.iitd.ac.in/~bishwa/LEC_PDF_774/LEC5.pdf · Concrete: Production (Pumping & Placing) B. Bhattacharjee CIVIL ENGINEERING DEPARTMENT