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Regensburg09.ppt1
Influence of theInfluence of theRheological PropertiesRheological Properties
on theon theFresh Concrete PressureFresh Concrete Pressure
Carsten BohnemannWolfgang Brameshuber
Institute of Building Materials Research, RWTH Aachen University (ibac)
18th Colloquium “Rheological Measurements of Building Materials“Regensburg, March 11-12, 2009
Regensburg09.ppt2
OutlineOutline
Influence of the rheological properties on the
fresh concrete pressure
Research methods for the fresh concrete pressure
Initial situation
Rheological equations of state
Summary
Regensburg09.ppt3
Fresh Concrete Pressure According to DIN 18 218Fresh Concrete Pressure According to DIN 18 218
fresh concrete pressure depends on:– velocity of placing– consistency
nonexistence of self-compactingand vibrated (F5 / F6) concretes
Regensburg09.ppt4
Influence Factors on the Fresh Concrete PressureInfluence Factors on the Fresh Concrete Pressure
– formwork geometry
– formwork roughness
– stiffness and density of the formwork
– formwork height
– ambient temperature– reinforcement
Procedural factors
Concrete factors
Further factors
Specific formwork factors
– consolidation of concrete
– velocity of placing
– pouring method
– fresh concrete density
– consistency / rheological properties
– fresh concrete temperature
– setting time
Regensburg09.ppt5
Flow Behaviour of Fluids and Ductile MaterialsFlow Behaviour of Fluids and Ductile Materials
Newtonian flow behaviour
• Newton: = ·
= 0 + k · n
Ductile flow behaviour
• Bingham:
• Herschel-Bulkley:
= 0 + pl ·
0
20
40
60
80
100
120
0 20 40 60 80 100 120
shear thickeningBingham
shear thinning
tana'=pl'
yield stress 0
shear stress
shear rate
tana=pl
Regensburg09.ppt6
Determination of Momentum CurvesDetermination of Momentum Curves
Bingham: T = g + h · N
T: shear stress
N: rotational speed
g: relative yield stress
h: relative viscosity
Viskomat NT
Regensburg09.ppt7
Display of Relevant Data of the Viskomat NTDisplay of Relevant Data of the Viskomat NT
0
40
80
120
160
0 5 10 15 20
0
10
20
30
40N in 1/min and T in Nmm
time in min
temperature in °C
rotational speed N
shear stress T
temperature
Regensburg09.ppt8
Approximation of Momentum Curves with Herschel-BulkleyApproximation of Momentum Curves with Herschel-Bulkley
n > 1: shear thickening
n < 1: shear thinning
n = 1: Bingham
T: shear stress
N: rotational speed
F: relative yield stress
k: slope factor
n: curve form factor
Herschel-Bulkley: T = F + k · Nn
0
10
20
30
40
50
60
0 50 100 150
flow curve
Herschel-Bulkley
T in Nmm
N in 1/min
F= 2.33 NmmV= 0.28 Nmm·min
Herschel-Bulkley T=2.33+0.24·N1.04
V: relative average viscosity
(slope at N = 60 rpm)
Regensburg09.ppt9
Description of ConcretesDescription of Concretes
Vibrated Concrete (VC)
VC-F5VC-F6
Self-Compacting Concrete (SCC)
SCC-PT-hvSCC-PT-lvSCC-VAT-hvSCC-VAT-lv
PT: powder typeVAT: viscosity agent typehv: high viscositylv: low viscosity
Regensburg09.ppt10
Mix DesignMix Design
0.420.40.520.470.560.47-w/ceq
1.5% per volumeair content
1.0-1.0stabilizer
1.51.21.72.72.13.9% per mass
(binder)
superplasticizer
172317501689174215841664aggregate
180170200180190160water content
75100250fly ash
395340300
kg/m³
CEM II/A-LL 42.5 R
87654321
VC
F6
VC
F5
SCC
VAT-lv
SCC
VAT-hv
SCC
PT-lv
SCC
PT-hv
content/value
unitmaterial
Regensburg09.ppt11
Description of MortarsDescription of Mortars
Mortar of the Vibrated concrete (VM)
VM-F5VM-F6
Self-Compacting Mortar (SCM)
SCM-PT-hvSCM-PT-lvSCM-VAT-hvSCM-VAT-lv
PT: powder typeVAT: viscosity agent typehv: high viscositylv: low viscosity
Regensburg09.ppt12
Momentum Curves of MortarsMomentum Curves of Mortars
0
5
10
15
20
25
30
35
40
45
50
0 20 40 60 80 100 120
SCM-PT-hv SCM-PT-lv
SCM-VAT-hv SCM-VAT-lv
VM-F5 VM-F6
rotational speed in 1/min
torque in Nmm
Regensburg09.ppt13
Herschel-Bulkley ApproximationHerschel-Bulkley Approximation
Herschel-Bulkley: T = F + k · Nn
SCM-PT-hv: T = 0.74 + 0.22 · N1.06
SCM-PT-lv: T = 0.02 + 0.13 · N0.98
SCM-VAT-hv: T = 0.34 + 0.19 · N0.93
SCM-VAT-lv: T = 0.00 + 0.24 · N0.78
VM-F5: T = 1.34 + 0.17 · N0.97
VM-F6: T = 3.07 + 0.30 · N0.82
Regensburg09.ppt14
Experimental Set-Up for Pressure Measurements Experimental Set-Up for Pressure Measurements
Regensburg09.ppt15
Measurement Method of Fresh Concrete PressureMeasurement Method of Fresh Concrete Pressure
detail load celllocation load cells
Regensburg09.ppt16
Research Program for Pressure MeasurementsResearch Program for Pressure Measurements
SCC-PT-lv10 2.0 m/hpump
SCC-PT-hv9
SCC-VAT-lv11
SCC-PT-lv810.0 m/h
SCC-PT-hv7
VC-F66
VC-F55
SCC-VAT-lv4
SCC-VAT-hv3
SCC-PT-lv2
2.0 m/hconcrete
bucket
SCC-PT-hv1
4321
velocity of placing
pouring method
concretewall
Regensburg09.ppt17
Pressure vs. Time – Wall 1Pressure vs. Time – Wall 1
0
10
20
30
40
50
60
70
0 0.5 1 1.5 2 2.5 3
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5load cell bottomload cell 2nd from bottomload cell 2nd from topload cell tophydrostatic pressurefilling level
pressure in kN/m²
time in h
interruptioninterruption
filling level in m
SCC-PT-hvconcrete bucket
vc= 2 m/h
Regensburg09.ppt18
Pressure vs. Time – Wall 2Pressure vs. Time – Wall 2
0
10
20
30
40
50
60
70
0 0.5 1 1.5 2 2.5 3
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5load cell bottomload cell 2nd from bottomload cell 2nd from topload cell tophydrostatic pressurefilling level
pressure in kN/m²
time in h
interruptioninterruption
filling level in m
SCC-PT-lvconcrete bucket
vc= 2 m/h
Regensburg09.ppt19
Pressure vs. Time – Wall 1 to 6Pressure vs. Time – Wall 1 to 6
0
10
20
30
40
50
60
70
0 0.5 1 1.5 2 2.5 3
SCC-PT-hvSCC-PT-lvSCC-VAT-hvSCC-VAT-lvVC-F5VC-F6hydrostatic pressure
pressure in kN/m²
time in h
load cell bottomconcrete bucket
vc= 2 m/hinterruption
interruption
Regensburg09.ppt20
Pressure vs. Time – Wall 1, 2, 7 and 8Pressure vs. Time – Wall 1, 2, 7 and 8
0
10
20
30
40
50
60
70
0 0.5 1 1.5 2 2.5 3
SCC-PT-hv, 2 m/hSCC-PT-lv, 2 m/hSCC-PT-hv, 10 m/hSCC-PT-lv, 10 m/hhydrostatic pressure
pressure in kN/m²
time in h
load cell bottomconcrete bucket
Regensburg09.ppt21
Pressure vs. Time – Wall 9, 10 and 11Pressure vs. Time – Wall 9, 10 and 11
0
10
20
30
40
50
60
70
0 0.5 1 1.5 2 2.5 3
SCC-PT-hv
SCC-PT-lv
SCC-VAT-lv
hydrostatic pressure
pressure in kN/m²
time in h
load cell bottompump
vc= 2 m/h
Regensburg09.ppt22
SummarySummary
Low influence of SCC type on fresh concrete pressure
Increasing pressure by decreasing the viscosity
High influence on fresh concrete pressure by velocity of placing
Hydrostatic pressure for formwork dimensioning at pumping
Decrease of pressure at the bottom during interruption
Fresh concrete pressure of SCC compared to VC significantly lower (concrete bucket, 2 m/h)
Low influence of rheological properties at higher velocity of placing or at pumping
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