Advances in Concrete Science in the Last 50 Years - ERMCO · Advances in Concrete Science in the Last 50 Years Surendra P. Shah ... Fiber Reinforced Concrete

Center for Advanced Cement-Based MaterialsNorthwestern University McCormick School of Engineering & Applied Science

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Advances in Concrete Science in the Last 50 Years

Surendra P. ShahWalter P. Murphy Professor (Emeritus)

Center for Advanced Cement-Based MaterialsNorthwestern University

Evanston, IL 60306, USA

04.06.2015 İSTANBUL


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Outlines

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Strength of Concrete1

2

3

5

Fracture and Cracking

Fiber Reinforced Concrete

Self-compacting Concrete

Micro to Nano


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Burj Dubai> 800 m (1/2 mile)

[courtesy of wikipedia.org]

Strength of Concrete

Concrete: achieving higher strength


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Water/Cement ratio

Com

pres

sive

Stre

ngth

Abram’s Law

Workable concrete

Unworkable concrete


Concrete: achieving higher strength


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Microstructural Changes in High Strength Concrete


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200

0

400

600

800

Max

imum

hei

ght (

inc.

spire

) [m

]

Water TowerPlace, Chicago

(262m)

Petronastwin towers,

Malaysia(452m)

Taipei101,

Taipei(508m)

Burj Khalifa,Dubai

(828m)

Lake PointTowers, Chicago

(197m)

311 S Wacker, Chicago(293m)

Completionyear1960 1970 1980 1990 2000 2010


Development of building height

High Strength Concrete (HSC)


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ASR


Higher strength? NOT enough. Durability is also important. High Strength Concrete (HSC)


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2000 4000 6000 8000 10000TOTAL CHARGE AT 6 HRS (COULOMBS)

0

4000

8000

12000

CO

MPR

ESSI

VE S

TREN

GTH

(PSI

) @ 4

0 D

AYS

Strength should not be used as the sole indicator of durability.


Compressive strength vs. Permeability High Strength Concrete (HSC)


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High Strength Concrete (HSC): Brittle failure


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Deflection

Composite

ConcreteSteel

Deflection

SteelDeflection

Concrete


Post-peak behavior of concrete



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Testing With feedback signals Feedback can be:

- Load- Axial displacement- Lateral displacement (circum.)

Closed-loop Testing



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Ultra-high strength concrete

Normal strength concrete



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Outlines

4


2

3

5




Micro to Nano


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Fracture & Cracking


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Stress

f’c

E

Strain

Stress

Strain

Elastic theory Ultimate state design

Fracture & Cracking

Development of Design theory

f’c


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Fracture & Cracking

Mindess, Young, Darwin

Fracture propagation in compression


17Lawler, Choi

Fracture propagation in compression

Fracture & Cracking


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Fracture & Cracking


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rate of fluid flow

permeability coefficientpressure gradient

surface areafluid viscosity

L thickness of solid

dq HAKdt L

dqdt

K ΔH

A

µ

µ

∆=

=

====

=

∆H

L

ACracks produced

with split cylinder test

Concrete

Load

Cracking and transfer properties: Water permeability

Fracture & Cracking

Darcy’s Law


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0 100 200 300 400 500 600

Crack Opening Displacement (microns)

1E-10

1E-9

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

1E-2

Perm

eabi

lity

Coef

ficie

nt (c

m/s

)

(~0.015 in)ACI limit

Fracture & Cracking

Cracking and transfer properties: Water permeability


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Third Point

L/3 L/3 L/3

P/2P/2

Center Point

L/2 L/2

P

3

dPL4 2bd12

maxr max 2

Mcσ= =I

P L3f' =MOR=σ =2 bd

2

123bd

2d

6PL

bdPLI

Mc

=σ

==σ DepthThird Point

Center Point

*Higher than direct tensile strength due to strain gradients

MOR: Modulus of Rupture

Fracture & Cracking

Fracture Mechanics: Fracture testing


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Failure stress of a wide plate

σ

σ

2aLEFM DOES NOT APPLY

LEFM VALID

aal

σf

σYS

σπfICKa=

Critical Stress Intensity FactorICK =

Fracture Mechanics


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Fracture & Cracking

Effective Crack Model: Crack variation across width


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LOA

D (P

)

CMOD

Ci

Cu

11

Ci ,

,

a E

C E a

o

u e

→

→Applied Load

ae aoCMOD

Fracture & Cracking

Effective crack model


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Strain

Stress

Crack width

Stress

Fracture & Cracking

Fictitious crack model


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Maximum crack width is often specified when durability is a concern.

Restrained shrinkage test: Ring test

Fracture & Cracking


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Outlines

4


2

3

5




Micro to Nano


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Fiber Reinforced Concrete (FRC)

– Steel– Polypropylene– PVA– Cellulose– Glass (Alkali resistant)– Carbon– Asbestos

SteelPolypropylene

Glass

Carbon

Asbestos

Fiber types


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TensileStress

Strain

Fiber-ReinforcedConcrete

Plain Matrix


Why fibers in concrete?


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Crack width in FRC



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• Pressurized water flow• Closed-loop tensile test


Testing of Cracked Concrete

Hybrid

Control

Micro fiberMacro fiber


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Deflection

Macro-fiber

Micro-fiber

Matrix

10 MPa

3 MPa

Stre

ssFiber Reinforced Concrete (FRC)


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Weight of beams with equal load carrying capacity (kg/m):140 112 467 530



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Tunnel wall improvement(2008)

PC box girder bridge (2002)

Slab in an airport runway (2010)


Ultra-high Performance Concrete (UHPC)


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Ultra-high Performance Concrete (UHPC)

Hypergreen Tower (Paris, France)Architect: Jacques Ferrier



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MWCNT

Carbon Nanotubes (CNTs) • A CNT is a sheet of graphite rolled up into a tube structure

– Multi walled (MWNT)Consist of multiple layers rolled up with diameter of 20-40 mm

Carbon Nanofibers (CNFs) • Carbon Nanofibers are cylinder nanostructures with graphite planes which

extend beyond the diameter of the nanofibers

20-4

0nm


Nanotechnology and FRC: CNTs and CNFs

60-1

50 n

m

CNFs SEM image of CNFs


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Fabio Matta, University of South Carolina

CNT and CNF Mortar NanocompositesP-CMOD Curves

0

50

100

150

200

250

300

350

400

450

500

0,00 0,01 0,02 0,03 0,04 0,05 0,06 0,07 0,08

Load

(N)

C.M.O.D. (mm)

M0.5+CNFs0.1% (SP/CNFs=4)M0.5+CNTs0.1% (SP/CNTs=4)M0.5

28 day specimens


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Konsta-Gdoutos et al, Cement and Concrete Composites, 2010

Autogenous shrinkage of CNT reinforced concrete



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Resistivity of CNT reinforced concrete

MWNT content, %

Res

istiv

ity, k

_ ·c

m



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Han et al., Nanotechnology, 2009


Smart cement based materials using CNTs


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Outlines

4


2

3

5




Micro to Nano


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Self-compacting Concrete (SCC)


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stre

ss (τ

)

τy

γshear rate ( )

• Low stress required to initiate flow:low yield stress (ty)

• Low stress required for continuous deformationlow viscosity

• Rheology of the matrix must be controlled to avoid particle segregation (i.e. coarse aggregates)

=γτη

Conditions for Self-Flowing Suspensions



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2.7 Pa 25.5 Pa 141.9 Pa31.9 Pa


Influence of yield strength


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• Matrix yield stress and viscosity must be optimized for self-flowing capability.

Self-flow zone

Poor workability

Particle segregation

Optimum rheologyfor self-flow η

∆ρ

τy

∆ρ

Optimum rheologyfor segregation resistance

Flow behavior: Rheology


Self-flow zone concept


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ACI 347: presumed lateral pressure should equal the hydrostatic pressure until the effect of formwork pressure isunderstood

Studies have shown that SCC can have pressure less than hydrostatic1-3 due to structural rebuilding

1. A. Assaad, et. al, Cement and Concrete Research, v.35, 20052. P. Billberg, et. al, Concrete International, v.27 (10), 20053. Y. Vanhove, et.al, Magazine of Concrete Research, vol. 56, 2004.


Formwork Pressure


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Mock Up Test (2007, Dante Galeota, and et al.)

Research in collaboration with Université de Sherbrooke and CTL

Formwork Pressure



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Pressure Sensors(capacity: 50psi = 344kPa)

Lab formwork(V~20 Liter, H= 45cm, D=23 cm)

Loading Cell

Simulation Range: Real scale column heights up to 20 m, and casting rates ranging from 0 m/hr to 25m/hr ( and more)

Formwork Pressure: Laboratory set-up for measurement



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*Slump flow: 60 ± 2cm

0% nanoclay

0.33% nanoclay

Formwork Pressure: Clay effect



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- Combines placing, consolidating, and finishing in one continuous process- Conventional SF paving requires:

• High stiffness concrete • External vibration – energy intensive!


Slipform (SF) Paving


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• Slipform paving durability issues arise due to internal vibration (loss of air content, segregation)

• Eliminate need for internal vibration by manipulating the mix design

VIBRATOR

SURFACE VIBRATOR


Durability Issues


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Chord length

Laser

FocusingLens

SapphireWindow

RotatingOptics

CouplingLens

Fiber

Fiber-Optic

Coupler

Gives information about Floc size indirect indication of flocculation

Scans highly focused laser beam across suspension and measure time duration of back scattered lightCluster range: 0.5 – 1200 μm


Laser Backscattering Measurement of Floc Size


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0 50 100 150 200 250 300 350 4000

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

Particle Size (um)

Pro

babi

lity

Den

sity

Fun

ctio

n

0 min5 min10 min15 min

Floc Size with shear rate of 1s-1

0 50 100 150 200 250 300 350 4000

0.01

0.02

0.03

0.04

0.05

Particle Size (um)

Pro

babi

lity

Den

sity

Fun

ctio

n

0 min5 min10 min15 min

Floc Size with Shear rate of 100s-1

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H.J. Yim, J.H. Kim and S.P. Shah, Cement Particle Flocculation and Breakage Monitoring under Couette Flow, CCR (in press)


Evolution of flocs with shear rate


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Outlines

4


2

3

5




Micro to Nano


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From Micro To Nano


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ITZ of Aggregate/Cement paste

Optical image SEM-BSE image

From Micro To Nano


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Nanoindentation on 6 Months Old Cement Paste: w/c 0.5

Image size: 60 µm x 60 µm Left image shows indent locations, right image shows elastic modulus in GPa

Unhydrated cement particle

From Micro To Nano

0

0.1

0.2

0.3

0.40

-5

5 -1

0

10 -

15

15 -

20

20 -

25

25 -

30

30 -

35

35 -

40

40 -

45

45 -

50

Prob

abili

ty

Young's Modulus (GPa)

CP w/c=0.5

High Stif fness C-S-H

CH (Ca(OH)2)Porous Phase

Low Stif fness C-S-H

Nano-mechanical properties

TRB Task Force AFN15T, Nanotechnology-Based Concrete Materials, Washington D.C., January 13, 201558

0

0,1

0,2

0,3

0,4

0 -5

5 -1

0

10 -

15

15 -

20

20 -

25

25 -

30

30 -

35

35 -

40

40 -

45

45 -

50

Prob

abili

ty

Young's Modulus (GPa)

CP w/c=0.5

CP+CNTs

CP+CNFs

High Stiffness C-S-H

CH (Ca(OH)2)Porous Phase

Low Stiffness C-S-H

MWCNTs /CNFs 0.048wt.% of cement

Nano-mechanical properties

TRB Task Force AFN15T, Nanotechnology-Based Concrete Materials, Washington D.C., January 13, 2015

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Atom Probe Tomography

B. Gault et al., Atom Probe Microscopy, Springer Series in Materials Science 160

Needle shape sample

Sample is ionized, atoms accelerated towards detector

setup

results

Composition Structure

Application to nano modified cement systems

n-CaCO3

Clinker surface

Hydration products due to n-CaCO3 seeding

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Things we did not discuss today

Things we did not discuss today

SensorsNon-destructive Testing (NDT)Supplementary Cementitious Materials (SCM)Constitutive ModelingHydration kinetics and modelingTransport propertiesEarly age propertiesNano-modificationSmart materials


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What is the ideal concrete?

Constructability

Sustainability

Crack free

Predictability

FRCCNT

SCC

pumping

RCA

nanomodification

SCM

modeling

strain-hardening composite

Internal curingMonitoring


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What is the ideal concrete?

Long lasting

Aesthetics

Maintainability

Economic

Self-healing

Coating

Rebar corrosion


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Thanks!

Documents

Advances in Concrete Science in the Last 50 Years - ERMCO · Advances in Concrete Science in the Last 50 Years Surendra P. Shah ... Fiber Reinforced Concrete