rheology testing of deep foundation concrete · thixotropy a thix and e.g. reduction of slump flow...
TRANSCRIPT
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TU München
Centre for Building Materials (cbm)
Rheology Testing of
Deep Foundation Concrete
Thomas Kränkel,
Dirk Lowke, Christoph Gehlen
European Federation of
Foundation Contractors
Sponsored by:
25. Workshop und Kolloquium: "Rheologische Messungen an Baustoffen"
02. und 03. März 2016, Regensburg
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Motivation
In situ made concrete piles and diaphragm walls
Structural
demands
Low water
permeability
Complete
form filling of the
cross-section
Full
embedment of
reinforcement
High segregation
resistance /
low bleeding tendency
Sufficient cohesion
to avoid
mixing with bentonite
Basic requirements for hardened concrete:
Resulting requirements for fresh concrete:
Bauer Spezialtiefbau
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Motivation
Defects and segregation
Inclusions Bleed channels Mattressing Segregation
Brown, Turner & Castelli:
FHWA-Report No. NHI-10-016. 2010
EFFC/DFI:
Best Practice Guide to Tremie Concrete
for Deep Foundations, 1st edition, 2016
EFFC/DFI:
Best Practice Guide to Tremie Concrete
for Deep Foundations, 1st edition, 2016 D. Lowke
3
To avoid these defects:
Detailed knowledge on concrete flow inside the foundation elements
during the whole placement process essential
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Problem
Recent changes in the DFC mix design
4
Wallevik O.H.: Rheology – A Scientific Approach to Develop
Self-Compacting Concrete. Pro 3rd Int. Symposium on SCC. 2003
Reduction of portland cement clinker
• CEM I CEM II CEM III
(reduced hydration heat development)
Increasingly amounts of additions
and (chemical) admixtures
• Fly ash, limestone powder
• Combination with superplasticizer, retarding
and/or workability retaining admixtures
Specially for excavations in great depths
• concrete placement is a considerably time-
consuming process
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No suitable test concept to measure
rheology/workability of fresh DFC onsite
• Reliable prediction of form filling based on common
onsite testing impossible
Slump flow test
Problem
Recent workability testing on construction site
5
Slump or flow table test often only acceptance
tests
• Advantage:
• Easy handling on-site,
• Well known
• Limitation:
• Only indirect characterization of yield stress,
• No information on viscosity and thixotropy
• Problem:
• Yield stress, viscosity and thixotropy affect form filling
Flow table test
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Aim
Set of tests for workability testing on construction site
6
Advanced concept for characterization of fresh Deep Foundation
Concrete (DFC)
Practicable usability (on-site testing) concerning testing of Workability,
Rheology and
Robustness properties
Ensure a reliable prediction of form filling properties in deep
foundations (bored piles and/or diaphragm walls)
Bauer Spezialtiefbau
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WP 1: Testing on construction site State of technology concerning rheology, workability and robustness of DFC
WP 2: Laboratory testing Effect of concrete composition on rheology, workability and stability
WP 3: Rheological characterization by means of simple onsite tests Correlation between onsite workability and rheological parameters
WP 4: Suitable test concept for fresh DFC based on rheology Development of a set of tests and corresponding acceptance criteria
ensure completely filling of the cross-section,
fully embedment of reinforcing steel,
avoid segregation and excessive bleeding
WP 1: Testing on construction site State of technology concerning rheology, workability and robustness of DFC
WP 2: Laboratory testing Effect of concrete composition on rheology, workability and stability
WP 3: Rheological characterization by means of simple onsite tests Correlation between onsite workability and rheological parameters
WP 4: Suitable test concept for fresh DFC based on rheology Development of a set of tests and corresponding acceptance criteria
ensure completely filling of the cross-section,
fully embedment of reinforcing steel,
avoid segregation and excessive bleeding
7
Work packages
Cement Water Addition Gravel Sand
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Workability / Rheology / Robustness
Workability loss
Initial thixotropic properties
Initial dynamic properties
Fresh concrete properties (mixing, transport, casting)
Reversible Structural build-up
at rest
Irreversible Structural build-
up at rest
Str
eng
th o
f str
uctu
re
Seconds/Minutes Minutes
Working plan for on-site and laboratory testing
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WP1: Testing on construction site State of technology concerning workability, rheology and robustness of DFC
www.europakarte.org
Rotterdam
London
Rastatt Paris
Berlin
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WP1: Testing on construction site – D-Walls
Strengthening work on two dikes in the Netherlands
B. Admiraal B. Admiraal B. Admiraal
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WP1: Testing on construction site – Bored piles
Foundation for a 60-storey residential skyscraper (London)
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Workability / Rheology / Robustness
Workability loss
Initial thixotropic properties
Initial dynamic properties
WP1: Testing on construction site State of technology concerning workability, rheology and robustness of DFC
Slump flow
test
L-Box
test
Dynamic vane
test
Flow table
test
Filtration
test
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WP1: Testing on construction site State of technology concerning workability, rheology and robustness of DFC
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Workability / Rheology / Robustness
Workability loss
Initial thixotropic properties
Initial dynamic properties
Slump flow test L-Box test
Result:
Reversible increase of structural
strength of the concrete at rest ► Measured by the reduced workability at
2nd measurement
1st Measurement ► Right after mixing
► Filling of slump cone and L-Box
► Rapid measurement after filling
Strength of sheared structure
2nd Measurement ► Right after mixing
► Filling of slump cone and L-Box
► 240 Seconds at rest (concrete
remains undisturbed in the
specimen)
► Delayed measurement
Strength of structure at rest
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τ0S = 0.81tR + 136
0
100
200
300
400
0 60 120 180 240 300
Sta
tic
yie
ld s
tre
ss
τ0S
[Pa
]
Time at rest [s]
WP1: Testing on construction site State of technology concerning workability, rheology and robustness of DFC
Workability / Rheology / Robustness
Workability loss
Initial thixotropic properties
Initial dynamic properties
Static vane test ► Static yield stress τ0S after different
times at rest tR
(tR = 30, 60, 120 and 240 sec at rest)
► Temporal increase in is a measure of
Thixotropy
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Workability / Rheology / Robustness
Workability loss
Initial thixotropic properties
Initial dynamic properties
1st Measurement ► Right after mixing
► Filling of specimen
► Rapid measurement after filling
Initial dynamic properties
Slump flow test L-Box test 2nd Measurement ► 2 - 6 hours at rest (concrete
remains undisturbed in the
specimen)
► Delayed Measurement
Delayed dynamic properties
Result:
Flow retention ► Measured by the reduced workability
at 2nd measurement
Dyn. vane test
WP1: Testing on construction site State of technology concerning workability, rheology and robustness of DFC
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Documentation to be done by participating contractors:
Wall has to be exposed and its quality (photo) documented
Information on Concrete composition
All parameters influencing the concrete flow
WP1: Testing on construction site State of technology concerning workability, rheology and robustness of DFC
Bartho Admiraal
Bartho Admiraal
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On site testing
Good m
ixes d
ue to c
ontr
acto
rs
photo
docum
enta
tion
Bad m
ixes d
ue to c
ontr
acto
rs
photo
docum
enta
tion
Workability loss
Initial thixotropic properties
Initial dynamic properties
WP1: Testing on construction site State of technology concerning workability, rheology and robustness of DFC
17
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Correlation between onsite workability and rheological parameters
Slump, slump flow
Flow time
Reduced workability
Find parameters for a realistic description of concrete flow in bored piles
and/or diaphragm walls
Dynamic yield stress
Plastic viscosity
Thixotropy
WP3: Rheological characterization of DFC by means of
simple onsite tests
18
vs.
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Correlation between onsite workability and rheological parameters
Dynamic yield stress τ0D and Slump flow diameter ds
WP3: Rheological characterization of DFC by means of
simple onsite tests
0
100
200
300
400
20 30 40 50 60 70 80
Dyn
am
ic y
ield
str
es
s τ
0D
[Pa
]
Slump flow ds [cm]
DFC on-site
DFC laboratory
Relationship for UHPC
0
100
200
300
400
20 30 40 50 60 70 80
Dyn
am
ic y
ield
str
es
s τ
0D
[Pa
]
Slump flow ds [cm]
DFC on-site
DFC laboratory
Relationship for UHPC
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Correlation between onsite workability and rheological parameters
Plastic viscosity µ and time to reach end of horizontal compartment of L-Box
WP3: Rheological characterization of DFC by means of
simple onsite tests
20
0
10
20
30
40
0 2 4 6
Pla
sti
c v
isc
os
ity [
Pa
. s]
Time to reach end of L-Box [s]
DFC on-site
DFC laboratory
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Correlation between onsite workability and rheological parameters
Thixotropy Athix and …
WP3: Rheological characterization of DFC by means of
simple onsite tests
21
Low thixotropyτ0S = 0,05tR + 72
High thixotropyτ0S = 0.81tR + 136
0
100
200
300
400
0 60 120 180 240 300
Sta
tic
yie
ld s
tre
ss
τ0S
[Pa
]
Time at rest [s]
Mix 1
Mix 2
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Correlation between onsite workability and rheological parameters
Thixotropy Athix and e.g. reduction of slump flow diameter at time at rest
WP3: Rheological characterization of DFC by means of
simple onsite tests
22
Low thixotropyτ0S = 0,05tR + 72
High thixotropyτ0S = 0.81tR + 136
0
100
200
300
400
0 60 120 180 240 300
Sta
tic
yie
ld s
tre
ss
τ0S
[Pa
]
Time at rest [s]
Mix 1
Mix 2
Low thixotropy
High thixotropy
50
52
54
56
58
60
0 60 120 180 240 300
Slu
mp
flo
w d
S[c
m]
Time at rest [s]
Mix 1
Mix 2
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τ
µ
Set of onsite tests and acceptance criteria for these tests
WP4: Suitable test concept / onsite workability test set for
fresh DFC based on rheology
23
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Dipl.-Ing. Thomas Kränkel
Centre for Building Materials
Technische Universität München
Centre for Building Materials