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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
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
–– 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
B. Bhattacharjee
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
–– 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
B. Bhattacharjee
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
–– 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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Types of PumpTypes of Pump
B. Bhattacharjee
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
– Mobile Boom Pump
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Pneumatic PlacerPneumatic Placer
B. Bhattacharjee
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
– 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
B. Bhattacharjee
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
–– 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
B. Bhattacharjee
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
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Rheology of Fresh Paste Rheology of Fresh Paste
B. Bhattacharjee
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
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
B. Bhattacharjee
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
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
B. Bhattacharjee
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
––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
B. Bhattacharjee
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
–– 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 Flow Concrete Flow
B. Bhattacharjee
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
–– 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
B. Bhattacharjee
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
Saturated
Transition
Unsaturated
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PumpabilityPumpability
B. Bhattacharjee
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
– Fines must be sufficient to resist passageof water i.e., blocked filter effect.
29B. Bhattacharjee
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
PumpabilityPumpability
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 =
30B. Bhattacharjee
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
PumpabilityPumpability
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
−=
31B. Bhattacharjee
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
PumpabilityPumpability
– PRESSURE BLEED TEST
125
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Effect of Pumping on concreteEffect of Pumping on concrete
B. Bhattacharjee
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
– Drier consistency
– Increase In Temperature
– Slight increase in air content
– No change in strength or shrinkage, although aluminum pipes may cause loss of strength
34B. Bhattacharjee
DEPARTMENT OF CIVIL ENGINEERING, IIT DELHI
Dos & Dos & DonDon’’ts in ts in concrete concrete HandlingHandling