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

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

2

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

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

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

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

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

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

8

WP1: Testing on construction site State of technology concerning workability, rheology and robustness of DFC

www.europakarte.org

Rotterdam

London

Rastatt Paris

Berlin

9

WP1: Testing on construction site – D-Walls

Strengthening work on two dikes in the Netherlands

B. Admiraal B. Admiraal B. Admiraal

10

WP1: Testing on construction site – Bored piles

Foundation for a 60-storey residential skyscraper (London)

11

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

12

WP1: Testing on construction site State of technology concerning workability, rheology and robustness of DFC

13

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

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

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

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

16

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

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.

19

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

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

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

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

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

Dipl.-Ing. Thomas Kränkel

Centre for Building Materials

Technische Universität München

thomas.kraenkel@tum.de

Centre for Building Materials