stabilizing highly flowable concrete against segregation ... · 2018-09-26 · stabilizing highly...

Stabilizing highly flowable

concrete against segregation

and water loss Dr. Oliver Mazanec

Head of Product Management, Admixture Systems Europe

London, 26. September 2018

24.10.2018 | The Concrete Society Events2

but, some additional challenges aroseFormulation robustness against raw material fluctuations

Shrinking availability of fly ash (900 Mio/to), slag (350 Mio/to) and sand which are required for stabilizing flowable concrete

Pronounced usage of inert SCMs, which reduces thixotropy and stability of concrete

Bleeding, segregation and undesired water loss occurred

PCE technology is basis for modern concrete structures,

PCEs changed the world of construction

Source: VDZ

Source: https://www.archdaily.com


Severe damage potentials

Structural: Reduced strength build up

Aesthetics: Chalking surfaces

Durability: Increased porosity/capillarity

With increasing fluidity in the mix, the tendency for construction materials to sediment & separate increases!

Why do we need stabilizers in construction industry ?

Construction applications using stabilizers

Cement pastes Mortar and grouts Concrete

Post-tension Self-levelling underlayments Self-Compacting concrete

Geo-technical Flowable repair mortars Underwater concrete

Remediation Machinery and Non-shrink grouts Hollow-core slaps

Flowable-fill Flowable floor screeds Deep Foundation concrete

Self-levelling

underlayments (SLU)

Flowing

floor screeds

Flowable and

Self-compacting concrete (SCC)

Post-tension

grouts

Stabilizers

in powder form for …Stabilizers in liquid or

powder form for …


Tremie concrete for

deep foundations

24.10.20185

What causes segregation and bleeding ?

| The Concrete Society Events

Concrete is a suspension of solids (cement, aggregates, sand) in water with a solid volumefraction between 0.4 and 0.8

Reduction of yield point reduces kinetic stabilisation of the cementitious suspension

sh

ea

r s

tres

s

/Pa

shear rate /s-1

blank

0.15 % PCE

0

0, PCE

yie

lds

tres

s

0

Rheograph( - - figure)

Stable area

Instable area

Water reducing

admixture

water

Reference mix

plastic viscosity

0 =𝐴0𝑎

𝑑² 𝐻²∙ 𝑓𝜎

∙2(− 𝑝𝑒𝑟𝑐)

𝑚(𝑚 −)

Yield Stress Model (Yodel)

J. R. Flatt et al: A Yield Stress Model for Suspensions

(2006)

w/o PCE

PCE

H,PCE

Cement surface

24.10.20186

Thixotropy is one key aspect for stable and robust concretes


vis

co

sit

y

& y

ield

str

ess

0

sh

ear

rate

time t

Shear phase Time at rest

ThixotropyBuild up of

viscosity and

yield stress

Mixing, transport,

placement

End of workability and

time until setting

24.10.20187

How to measure thixotropy of mortar and concrete ?


0

100

200

-90 -60 -30 0 30 60 90 120

Sh

ea

r s

tres

s (

Pa

)

0,1

1

10

100

-90 -60 -30 0 30 60 90 120

Sh

ea

r ra

te (

s-1

)

Time (s)

Time (s)

Athix

0,120

0,30

structure break thixotropic structure break

Rotational rheometer

equiped with vane geometry

Mazanec, O: PhD Thesis, TUM, 2012

24.10.20188

Thixotropy of cement compared to inert limestone powder


0

20

40

60

80

100

0 30 60 90 120

dyn

am

ic&

sta

tic

yie

lds

tres

s (

Pa

)

time at rest tP (s)

Thixotropy

CEMENT

0,0

0,2

0,4

0,6

0,8

1,0

0 30 60 90 120

ble

ed

ing

wa

ter

(mm

)

time at rest tP (min)

Bleeding

CEMENT

Limestone powder*)

Limestone powder*)

50% Cement / CEM I 52,5 N

50% Fine Sand

0,13% bwoc PCE

w/c ratio = 0,35

* in artifical pore solution

24.10.20189

Origins of cement thixotropy


Roussel, N.: Origins of thixotropy, Cem Con Res (2012), pp. 155

Lowke, D.: Sedimentationsverhalten von SVB, PhD Thesis (2013), TUM

0

20

40

60

80

100

0 30 60 90 120

dyn

am

ic&

sta

tic

yie

lds

tres

s (

Pa

)

time at rest tP [s]

Thixotropy

CEMENT

Limestone powder*

tP = 10 s

layer thickness

of adsorbed PCE

colloidal interaction of cement

particles in the dormant period

tP = 100 s

growths of first

nucleation products

(e.g. CSH, ettringit)

ongoing hydrates

nucleation

tP = 300 s

nucleation

ampliyfing

2eff

d

early hydrates which forms preferentially

at the contact points between cement

grains

Why is cement a

thixotropic material ?

* in artifical pore solution

50% Cement (CEM I 52,5 N)

50% Fine Sand

0,13% bwoc PCE

w/c ratio = 0,35

24.10.201810

Addition of C-S-H based accelerator enhances cement thixotropy


0

20

40

60

80

100

0 30 60 90 120

dyn

am

ic&

sta

tic

yie

lds

tres

s (

[Pa

)

time at rest tP (s)

Thixotropy

CEMENT

CEM + MX-Seed**

Limestone powder*

**MasterX-Seed 100: accelerator

based on nano C-S-H seeds

tP = 10 s

layer thickness

of adsorbed PCE

colloidal interaction of cement

particles in the dormant period

tP = 100 s

growths of first

nucleation products

(e.g. CSH, ettringit)

ongoing hydrates

nucleation

tP = 300 s

nucleation

ampliyfing

d

early hydrates which forms preferentially

at the contact points between cement

grains

Roussel, N.: Origins of thixotropy, Cem Con Res (2012), pp. 155

Lowke, D.: Sedimentationsverhalten von SVB, PhD Thesis (2013), TUM

24.10.201811

Parameters effecting bleeding and segregation of concrete


The rate of sedimentation can be influenced by

▪ water/cement ratio

▪ particle size distribution

▪ paste volume

▪ cement and SCM type

▪ admixture type and dosage

▪ stabilizer or viscosity modifying admixtures (VMA)

Benefits of stabilizer & VMAs

▪ stabilization of solid particles

no sedimentation, no bleeding

▪ improved robustness

tolerates water deviations & raw material deviations

▪ individual adjustment of rheological properties

better control on desired rheology profile

▪ dosage efficient compared to mineral fillers

economic benefitw/o stabilizer with stabilizer

frac

tio

n

particle size

Cement ACement B

A wide particle size distribution usually gives

a higher stability than narrow due to better

particle packing (> m)

Viscosity Modifying Admixtures - Technology overview

24.10.201812

Product

MasterMatrix SDC 100

Mode of action

Water soluble polymer

Hydrogen bonding of water

Properties

Imparts no shear-thinning

High water retention

Hydrogen bonding

Product

MasterMatrix SCC 210

Mode of action


Forms complex molecular aggregates

and polymer entanglement

Properties

Imparts highly shear-thinning

Sligthly water retention

Self Association Aggregation/Flocculation

Product

Polyarcylamids

Mode of action


Flocculation of solid particles

Properties

Imparts no shear-thinning

Low water retention

yie

lds

tre

ss

Stable area

Instable area

plastic viscosity

Stable area

Instable area

plastic viscosity

yie

lds

tre

ss

Stable area

Instable area

plastic viscosity

yie

lds

tre

ss

?

cement grain

Rheological profile of stabilizers in aqueous salt solution

Self Association Hydrogen Bonding

Highly shear-thinning: Easy mixing

and pumping and excellent

stabilization of coarse particles at rest

No shear-thinning: Excellent water

retention at high static pressure

24.10.201813 | The Concrete Society Events

Rheological profile of stabilizers in aqueous salt solution

0,001

0,01

0,1

1

10

100

0,01 0,1 1 10 100 1000

log

ap

pare

nt

vis

co

sit

y (

Pas

)

finishing/placement pumping mixing

log shear rate (s-1)

Self association

(highly shear thinning)

Hydrogen bonding

(no shear thinning)

Rheometer Anton Paar, Type MCR 302

equiped with coaxial cylinder

0

500

0 720

(s-1)

Rotational test(apparent viscosity)

300

time (s)


0,01 1 100

log shear rate /s-1

6.0 10.0

15.0 20.0

40.0

c/g·L-1

0,001

0,01

0,1

1

10

100

0,01 1 100

log

ap

pare

nt

vis

co

sit

y

/Pa

·s

log shear rate /s-1

0.2 0.5

2.0 4.0

c/g·L-1

Self Association

Apparent viscosity for various VMAs

as function of shear rate (aqueous pore solution)

Hydrogen Bonding

Stability criteria:

20 - 40 mPas


Self Association: imparts

highly shear-thinning which

increases with concentration

Hydrogen Bonding: imparts no shear-

thinning at low concentration and weak

shear-thinning at high concentration

Self Association

Hydrogen Bonding

Rheometer MCR 302

from Anton Paar

coaxial cylinder

Stock solutions were prepared by dispersing

dry samples for 12 h in distilled water

Creep recovery(Zero-shear viscosity)

1

10

100

1000

10000

0 60 120 180 240 300

time (s)

J (1/Pa)

0 =60𝑠

𝐽240− 𝐽180

Xu, L. et al: Carbohydrate Polymers, (2015)

= 0.1 Pa

Mechanism of shear thinning

Creep recovery test


0,001

0,01

0,1

1

10

100

1000

0,01 0,1 1 10 100

ze

ro-s

he

ar

vis

co

sit

y

0/P

a·s

C/g·L-1 (active polymer)

Diutan Gum

Synthetic Copolymer

c*: Self Association (SA) << Hydrogen Bonding (HB)

Mechanism of shear thinning

Critical aggregation concentration c*

no self association

▪ Self Association (SA)

c* 0.12 g·L-1

▪ Hydrogen Bonding (HB)

no polymer interaction

Distilled water

Hydrogen Bonding

c*: critical aggregation concentration

Self Association


c* 0.12 g·L-1

self association

no polymer interaction

recommended

dosage

0,001

0,01

0,1

1

10

100

1000

0,01 0,1 1 10 100

Comparison zero shear vs. apparent viscosities

SA zero shear viscosity SA apparent viscosity @ 7.8 1/s

HB zero shear viscosity HB apparent viscosity @ 7.8 1/s

Cg/L-1 (active polymer)

typical industrial

dosages

Effect of concentration on apparent viscosity at

high shear rate vs. zero shear viscosity

@ Typical industrial dosages

Self Association results in

▪ reduced dosage demands

▪ increased viscosity

▪ shear thinning

Hydrogen bonding results in

▪ higher dosage demands

▪ solely increase of viscosity

shear

thinningSelf Association (SA)

Hydrogen Bonding (HB)


Link between concrete handling and rheological measurements

0.01 0.1 1 10 100

segregation visibility limit finishing /

placement

mixing /

high pressure

pumping

co

nc

rete

ha

nd

lin

gte

st

slump flow

&

= yield stress

funnel flow

t

= viscosity

log shear rate /


0,01

0,1

1

10

100

0,01 1 100

log

vis

co

sit

y (

Pas

)


Self Association

Hydrogen

bonding

Aiad, I.: CCR, 2003, p. 1229-1234

Stabilizing self compacting concrete against

bleeding and sedimentation

20 24.10.2018 | The Concrete Society Events

0,01

0,1

1

10

100

0,01 0,1 1 10 100 1000

log

vis

co

sit

y (

Pas

)


Self Association

(shear thinning)

Hydrogen bonding

(no shear thining)

Shear rate in application

SCC

Flo

w v

alu

e

Superplasticizer dosage

PCE saturation(mixture without stabilizer)

0.0 0.6 0.7 0.8 0.9 1.00.1 0.2 0.3 0.4 0.5

particle surface covering with PCE

How to find the right superplasticizer and stabilizer dosage?

75 cm

optimal

SP dosage

no flow

Example: SCC (target consistency: a ≥ 70 cm)

optimal flow

no sedimentation

70 cm+ Stabilizer


C35/45 (Precast)

350 kg/m³ CEM I 52.5 N

100 kg/m³ Limestone powder

w/c ratio = 0,49

Stabilizing of self compacting concrete

with low paste volume (VPaste = 318 l/m³)


200

300

400

500

600

700

800

0 15 30 45 60

slu

mp

flo

w a

(m

m)

time (min)

w/o stabilizer(1,8% bwoc PCE)

2g/L stabilizer(2,0% bwoc PCE)

6,2 6,4

0

2

4

6

8

10

w/o stabilizer(1,8% bwoc PCE)

2g/L stabilizer(2,0% bwoc PCE)

t 500-t

ime

(s

)

*PCE = MasterGlenium ACE 430

**SR = R&D Product

(1,2% PCE + 1,1% SR)

(1,4% PCE + 1,3% SR)

(1,2% PCE + 1,1% SR) (1,4% PCE + 1,3% SR)

a

0,2 g/L Self Association stabilizer

2 g/L MMatrix SCC 2100,2 g/L Self Association stab.

t500

Stabilizing of self compacting concrete with low paste volume


w/o Stabilizer

with Self Association

stabilizer(0,2 g/L = 35 g/m³)

Strong bleeding and

sedimentation!

No separation,

robust concrete!

R&D MasterMatrix for drilled pile concrete


Stabilizing tremie concrete for deep foundations

against water loss

0,01

0,1

1

10

100

0,01 0,1 1 10 100 1000

log

vis

co

sit

y (

Pas

)


Self Association

(shear thinning)

Hydrogen bonding

(no shear thining)

Shear rate in application

Example: Drilling with steel casingDeep foundations (piles and diaphragm walls)

Inserting the steel

casing for the upper

section of the drilled

pile (ensures stable

collar)

Excavation with

drilling bucket.

Stabilization of the

borehole wall with

steel pipe

Installation of the

reinforcement cage

Concreting the

pile with the

pouring tube.

Concreting from

base of the hole.

Removal of the

steel casing using

the drill rig


Drilled piles: h = 5 - 30 m

High static pressure

water is pressed out

stabilizer with good water

retention properties is

required

Concrete requirements

▪ C40/50, 360 kg/m³ CEM III, w/c = 0,45

▪ Slump flow a = 600 mm, 6 h

▪ Bleed water control static

▪ Bleed water control under pressure

high static load

water is

pressed out

Test set-up to determine water filtrared from pressurized fresh concretebased on standard testing for drilling fluids in accordance with API RP 13B-1


Ex

tre

me

hig

hsh

are

rate

/

Best EFFC/DFI Best Practice Guide to Tremie Concrete for Deep Foundations, 2016

Bauer filter press

Water retention of different stabilizer in tremie concrete

for deep foundations


Shear rate in filter press

Hydrogen Bonding results in

increased viscosity at high shear

rates which improves water retention

under pressure

300 kg/m³ CEM III A 42,5 N

100 kg/m³ Fly ash

w/c ratio = 0,68

EXELLENT

ACCEPTABLE

Self Association

Hydrogen

bonding

42,0

19,5

11,0

5,8

1,4

0

10

20

30

40

50

wa

ter

los

s (

ml)

Slump Flow

acc. to DIN EN 206

a = 600 50 mm (6 hours)

0,01

0,1

1

10

100

0,01 1 100

log

vis

co

sit

y (

Pas

)


NOT ACCEPTABLE

*Hydrogen Bonding for Deep Foundation Concrete: research product, product launch is scheduled for 2019

**

▪ The high dispersing power of can PCEs lead to a higher sensitivity of the concrete mix against bleeding and segregation

▪ The right balance between high fluidity and high segregation resistance can be obtained by a proper rheological behaviour (yield point, thixotropy and viscosity)

▪ Self assembling stabilizers induce a shear thinning behaviour in theconcrete mix which help to stabilize against sedimentation that happens at low shear rate (e.g. Self Compacting Concrete and Underwater Concrete)

▪ Hydrogen bonding stabilizers have constant properties at different shearrates which is benefical to stabilize against water loss under high pressure(e.g. Tremie Concrete for deep foundations)

Conclusions


stabilizing highly flowable concrete against segregation ... · 2018-09-26 · stabilizing highly...

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