A Chemical Admixture with

Carbon Nanotubes

Yuan Gao1

David J. Corr2

Maria S. Konsta-Ddoutos3

Surendra P. Shah4

ACI Spring Convention, Salt Lake City, 2018

1. PhD Candidate, Civil Engineering Department, Northwestern University2. Professor, Civil Engineering Department, Northwestern University3. Professor, Civil Engineering Department, Democritus University of Thrace4. Professor(Emeritus), Civil Engineering Department, Northwestern University

• Background

• Effect of CNT in cement composites– Mechanical properties

– Autogenous shrinkage, shrinkage cracking

– Reinforcement corrosion

• Processing of CNT suspension– Dispersion

– Characterization

– Chemical admixture

• Conclusions

Content

• Background

• Effect of CNT in cement composites– Mechanical properties

– Autogenous shrinkage, shrinkage cracking

– Reinforcement corrosion

• Processing of CNT suspension– Dispersion

– Characterization

– Chemical admixture

• Conclusions

Content

Background

Carbon nanotube/nanofiber

• Young’s Modulus: 0.6-1 TPa

• Tensile Strength: ~100 GPa

1. Ozkan T, Naraghi M, Chasiotis I. Mechanical properties of vapor grown carbon nanofibers. Carbon 2010;48:239–44.2. Mordlkovich VZ. Carbon nanofibers: a new ultrahigh-strength material for chemical technology. Theor Found Chem Eng 2003;37(5):429–38.

Multiwall Carbon Nanotube Carbon Nanofiber TEM of Carbon Nanofiber

Dispersion

Challenge of Using CNTs/CNFs

Small Dosage:

0.08-0.15 wt%

(to cement weight)

Cost

• Background

• Effect of CNT in cement composites– Mechanical properties

– Autogenous shrinkage, shrinkage cracking

– Reinforcement corrosion

• Processing of CNT suspension– Dispersion

– Characterization

– Chemical admixture

• Conclusions

Content

Mechanical Properties

Flexural Test Compression Test

D

H

2x2x8 cm 10x20 cm

Flexural Test

0

1

2

3

4

5

6

7

8

9

3 day 7 day 28 dayF

leu

xu

ral

Str

eng

th (

MP

a)

Plain Cement Paste

CP+0.1 wt%CNF

Cement Paste(w/c=0.485:1)

0

2

4

6

8

10

12

3 day 7 day 28 day

Yo

un

g's

Mo

du

lus

(GP

a)

Plain Cement Paste

CP+0.1 wt%CNF

Young’s Modulus Flexural Strength

Flexural Test

0

5

10

15

20

25

30

3 day 7 day 28 day

Yo

un

g's

Mod

ulu

s (G

Pa)

Plain Mortar

M+0.1 wt%CNF

0

1

2

3

4

5

6

7

8

9

3 day 7 day 28 dayF

leu

xu

ral

Str

eng

th (

MP

a)

Plain Mortar

M+0.1 wt%CNF

Mortar(w/c/s=0.485:1:2.75)

Young’s Modulus Flexural Strength

Compression Test

Concrete(w/c/s/a.g=0.51:1:2.46:3.5)

0

10

20

30

40

50

60

Young’s Modulus (GPa) Compressive Strength (MPa)

Plain Concrete

0.1 wt% CNF + Concrete

28 days

Mechanical Properties

Improvement

TestsCNF Volume

Fraction (%)

Young’s

Modulus

Improvement

(%)

Cement Paste

(CP)Flexural 0.083 21

Mortar (M) Flexural 0.036 34

Concrete (C) Compression 0.022 29

SEM/EDS on Interface

Hydration Products Ca/Si Ratio

Calcium-Silicate-Hydrate (C-S-H) 0.8~2.5

Calcium Hydroxide (CH) >10

Ettringite (AFm) >4.0

Bulk Paste

Interface Agg

SEM/EDS on Interface

Jeddah Tower (Jeddah)

E: 58 GPa (8500 ksi)

Mechanical Properties Improvement

0 50 100 150 200

0

10

20

30

40

50

60

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0 5 10 15 20 25 30

Compressive Strength (MPa)

You

ng'

s M

od

ulu

s (G

Pa)

You

ng'

s M

od

ulu

s (k

si)

Compressive Strength (ksi)

Cost

Sustainability

Stiffness

𝑬𝒄 = 𝟓𝟕𝟎𝟎𝟎 𝒇′𝒄

Mechanical Properties Improvement

0 50 100 150 200

0

10

20

30

40

50

60

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0 5 10 15 20 25 30

Compressive Strength (MPa)

You

ng'

s M

od

ulu

s (G

Pa)

You

ng'

s M

od

ulu

s (k

si)

Compressive Strength (ksi)

Concrete with CNFs

Compressive Strength: 7.3 ksi (50.5 MPa)Young’s Modulus:

6700 ksi (46.8 Gpa)

𝐸𝑐 = 57000 𝑓′𝑐

Cost

Sustainability

Stiffness

-900

-800

-700

-600

-500

-400

-300

-200

-100

0

0 0.5 1 1.5 2 2.5 3

Au

toge

no

us

Shri

nka

ge(μ

ε)

Time(days)

Autogenous Shrinkage of High Performance Mortar with or without CNF

Autogenous Shrinkage

Measurement

Plain Mortar

0.05 wt% CNF

w:c:s=0.34:1:1.75

25% Reduction

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Cra

ck W

idth

(mm

)

Time(days)

Restrained Ring Test of High Performance Mortar with or without CNF

Shrinkage Cracking

Plain Mortar

Start cracking w:c:s=0.34:1:1.75

0.05 wt% CNF

29% Reduction

Microscope

Half Cell Potential(mV)

Corrosion Probability

0-200 No corrosion

200-350 Possible corrosion

350-500 Corrosion

>500 Strongly Corroded

Reinforcement Corrosion

Reinforcement Corrosion

M .S. Konsta-Gdoutos, G. Batis, P.A. Danoglidis, A. K. Zacharopoulou, E. K. Zacharopoulou, M.G. Falara, S.P. Shah, Effect of CNT and CNF loading and count on

the corrosion resistance, conductivity and mechanical properties of nanomodified OPC mortars, 2017. doi:10.1016/j.conbuildmat.2017.04.112.

0.1 wt% CNTs could increase the resistance to corrosion

Hal

f-ce

ll P

ote

nti

al (

mV

)

• Background

• Effect of CNT in cement composites– Mechanical properties

– Autogenous shrinkage, shrinkage cracking

– Reinforcement corrosion

• Processing of CNT suspension– Dispersion

– Characterization

– Chemical admixture

• Conclusions

Content

Processing of CNT Suspension

Poor Dispersion Good Dispersion

Existing Dispersion Methods

• The chemical approach

– Non-covalent methods

– Covalent methods

• The mechanical approach

– Ultra-sonication

– High shear mixing

The Chemical Approach

covalentfunctionalization

noncovalent functionalization

The Mechanical Approach

Ultra-sonication Probe

Shear Mixing

Dispersion Characterization

1. Linqin Jiang, Lian Gao, Jing Sun, “Production of aqueous colloidal dispersions of carbon nanotubes,” Journal of Colloid and Interface Science, Volume 260, Issue 1, 2003, Pages 89-94,

Figure 2. Typical absorption curve for CNTs1Figure 1. Schematic of Ultraviolet-visible Spectroscopy

Characterization

Ultraviolet Visible Spectroscopy (UV-Vis)

Dispersion

A combination of the use of superplasticizer and

ultrasonication

S.P. Shah, M.S. Konsta-Gdoutos, Z.S. Metaxa (2016), Highly-dispersed carbon nanotube-reinforced

cement-based materials, US9499439B2

Processing of CNT Suspension

Water CNT powder Ultrasonication

CNT suspension Ultraviolet-vis spectroscopy

Superplasticizer

Chemical Admixture

• Small dosages of CNTs (0.08-0.15 wt%)

• Nano modification of the hydration

products

Conclusions

• CNTs significantly improve the mechanical

properties, such as flexural strength, Young’s

modulus

• CNTs reduce autogenous shrinkage and

shrinkage cracking

• CNTs increase the resistance to reinforcement

corrosion

• Good dispersion has been obtained in lab scale

• Dispersion needs to be scaled up for industry

application

Thanks!

Thanks!