Rheology and Mix Design - École Polytechnique Fédérale ...documents.epfl.ch/users/s/st/ston/www/6 Rheology.pdf · Rheology and Mix Design. Aurélie FAVIER ... Outline • Introduction

Aurélie FAVIER| 2015 1

Rheology and Mix Design

Aurélie FAVIER| 2015


Outline

• Introduction

• Basics on Rheology

• Overview on simple concrete rheology tests

• Flows regime in cementitious materials• Interactions • Consequences and admixtures

• Mix Design of Concrete


Introduction


Filling a mold

Casting Visquous fluid

Fluid concreteOrdinary concrete

From N.Roussel


Back to basics

• Definition about rheology:• science of flow and deformation of matter.• Linked between the strain speed and the applied stress

𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 𝑆𝑆𝑆𝑆𝑟𝑟𝑆𝑆 =𝑉𝑉𝑆𝑆

𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 𝑠𝑠𝑟𝑟𝑆𝑆𝑆𝑆𝑠𝑠𝑠𝑠 = 𝜑𝜑.𝑔𝑔. 𝑆𝑆. sin(𝜃𝜃)

Flow speed V

Density

Inclination

Depth


Behaviour’s laws

• To link stress and shear rate, we introduce some behaviour’s equation. The simplest is Newtonian fluid.


Yield stress fluid

• Yield stress for ordinary concrete : thousands of Pa• Yield stress for ordinary mortar : hundreds of Pa• Yield stress for cement paste : Pa


How to measure yield stress


Slump


Slump


Slump





Behaviour type


Interactions

• Differents interactions:• Brownian motion• Collloidal interactions• Hydrodynamic interactions• Direct contacts


Parameters

• d particles diameter around 10 microns• 𝜌𝜌𝑝𝑝 density of cement around 3.1• µ0 suspending fluid ex. Water 1mPas at 25°C• Φ volume fraction of solid• W/B

Φ = (1 + 𝜌𝜌𝑝𝑝W/𝜌𝜌𝐸𝐸B)-1


Thermal agitation

• The random movement of microscopic particles suspended in a liquid or gas,caused by collisions with molecules of the surrounding medium.

𝑘𝑘 𝑇𝑇 𝑤𝑤𝑤𝑤𝑟𝑟𝑆 𝑘𝑘 𝐵𝐵𝐵𝐵𝐵𝐵𝑟𝑟𝐵𝐵𝐵𝐵𝑆𝑆𝐵𝐵𝐵𝐵 𝑐𝑐𝐵𝐵𝐵𝐵𝑠𝑠𝑟𝑟𝑆𝑆𝐵𝐵𝑟𝑟4.10-21 J at 20°C


Thermal agitation

• d-3 = number of particles in 1 cubic meter

• In Pa.s𝑘𝑘𝑘𝑘�̇�𝛾𝑑𝑑3


Colloïdal interactions

In physical chemistry, the van der Waals force (or van der Waals' interaction), named after Dutch scientist Johannes Diderik van der Waals, is the sum of the attractive or repulsive forces between molecules (or between parts of the same molecule) other than those due to covalent bonds, or the electrostatic interaction of ions with one another, with neutral molecules, or with charged molecules. The resulting van der Waals forces can be attractive or repulsive. (Wikipedia)



• Electrostatic forces The surface of particles are positively charged repulsion

• Steric effectIf you change particles charges by adding polymers or the interstitial liquid , you can modify the suspension



At short distance the attractive Van der Waals forces dominate the electrostatic repulsion.

Moreover, Van der Waals forces dominate the Brownian motion.

𝜃𝜃 ≅ 𝐴𝐴0𝑎𝑎∗𝑑𝑑𝐻𝐻2 ≅ 10-16 J


Defloculation

As attractives forces dominate the system flocculation

To deflocculate , we use plasticizers.


HPCHigh Performance

Concretes

UHPRC/UHPFCUltra High Performance

Reinforced / Fiber Concrete

Shotcrete SCCSelf Compacting

Concretes

Recent development linked to the SP addition



Historical development

Vinyl Copolymer* CH CH CH2 CH *

COONaCH2 CO

n

CO

NR1 R2

N

R3 R4

19401950

19601970

19801990

20001930

2010

Poly-Carboxylate-Ether(PCE)

* CH2 C CH2 C *

R

m

R

n

COOH CO-X-(CH2CHRO-)y R

Melaminsulphonate

Naphthalinsulphonate

CH2

*

SO3Na

n

N N

NN N

NH

* CH2

CH2SO3Na

CH2X CH2Y

n

Carbohydrates

Ligninsulphonates O C

MeO

C CNa2S2O5 O C

SO3NaMeO

C C

C

C

C

C

CH2OH

COOM

OHH

HOH

OHH

OHH


How ?

• Bingham fluid

• By adding SP , we decrease the yield stress

•+= γµττ p0

SP


Forces interpaticulaires

•Van der Waals Forces (attractives)

Superplasticizers:

• Electrostatic effect to create repulsion

• Electrosteric effect depending on size and conformation of polymers


Effect of plasticizer on ratio W/B

E/C

Année


Self compacting concrete

30

easy to cast

no bleeding

no vibration needs


Construction speed



But….

33

[Zingg et al., 2009]


Conclusion about colloidal forces

• In Pa.s𝐴𝐴0𝑎𝑎∗

�̇�𝛾12𝐻𝐻2𝑑𝑑2


Hydrodynamic forces

• When you increase the shear rate the viscous dissipation increases.

• And the energy of the viscous dissipation :

𝜇𝜇0�̇�𝛾𝑓𝑓 Φ


Hydrodynamic forces

• In dilute system (W/B >6):• Einstein equation:𝑓𝑓 Φ = 1 + 2.5 Φ

• In concentrated suspensions• Krieger Dougherty relation: 𝑓𝑓 Φ = (1 − �Φ Φ 𝑚𝑚)-q


Hydrodynamic forces

• In Pa.s𝜇𝜇0𝑓𝑓 Φ


Inertia

• In high concentrated suspension

• Kinetic energy : 𝜌𝜌𝑝𝑝𝑑𝑑3𝑉𝑉2

• With 𝑉𝑉 = ̇𝑑𝑑𝛾𝛾𝑓𝑓 Φ

• So energy from inertia : 𝜌𝜌𝑝𝑝𝑑𝑑5�̇�𝛾2𝑓𝑓2 Φ

• In Pa.s 𝜌𝜌𝑝𝑝𝑑𝑑2�̇�𝛾𝑓𝑓2 Φ


Sum of energy


Volume fraction

• The numbers of particles plays an important role : inertia but also direct contacts.



Other admixtures


Viscosity agents

• Issue:• To avoid the sedimentation• To increase water retention

•Solutions:• Addition of viscosity agents such as cellulosic ethers, glucose, natural gums


How it works?

C. Brumaud 2011


Air entrainers

• Issue:• Increase of gel resistance

•Solutions: • Addition of air entrainers such as sulfonates or organic fatty acids, they are

anionic

http://www.explorations-architecturales.com/

Lemoniteur.fr


Effect on rheology

• For ordinary concrete , yield stress is around 2000Pa, air entrainer can help the rheo thinning.

• For self compacting concrete with yield stress close to 50 Pa, air entrainerhelps the shear thickening of the system


References

• Roussel lectures ENPC• Flatt lectures ETH

• Favier (2013) PhD dissertation• Brumaud (2011) PhD dissertation


Mix design


Dreux Gorisse


Bolomey method

• Take in consideration the cement content

• 𝑃𝑃(𝑝𝑝𝑆𝑆𝑆𝑆𝑐𝑐𝑆𝑆𝐵𝐵𝑟𝑟𝑆𝑆𝑔𝑔𝑆𝑆 𝐵𝐵𝑓𝑓 𝑟𝑟𝐵𝐵𝑟𝑟𝑆𝑆𝐵𝐵 𝑑𝑑𝑆𝑆𝑑𝑑 𝐵𝐵𝑆𝑆𝑟𝑟𝑟𝑟𝑆𝑆𝑆𝑆) = 𝐴𝐴 + (100 − 𝐴𝐴) 𝑑𝑑𝐷𝐷


Software

• BetonLab pro ( also available for free but with restrained conditions)

• Based on compaction index

• EMMA

• Optimisation of packing


Bolomey and SIA

• Swiss standard :

• SIA norm : curve of Fuller B ⇒ 𝑃𝑃 = 100 𝑑𝑑𝐷𝐷

• But cement is not included : SIA gives a minimum cement content 350kg/m3


Loi de Feret, 1896

Résistance à lacompression

Constante,:Fonction de l‘âge, mode de conservation et liant

Volumes de:c – cimente – eauv – vides

R = K cc + e + v

2

R = K c /(e + v)c / e + v( )+1

2


Loi de Bolomey

Pour v < ~2%

R = K CE + V

− K '

−×= 5.0

ECGR cσ


Powers

En fonction du nombres de paramètres inconnus (a et α), cetteformule n’est pas pratique à utiliser

α = fraction du ciment hydraté

Équivalent à:

Ou P = porosité:

R = a αcαc + e + v

3

R = a 1− P( )3

Documents

Rheology and Mix Design - École Polytechnique Fédérale ...documents.epfl.ch/users/s/st/ston/www/6 Rheology.pdf · Rheology and Mix Design. Aurélie FAVIER ... Outline • Introduction