Hershey LodgeHershey Lodge

Preconference SymposiumPreconference Symposium17 March 200817 March 2008

Hershey LodgeHershey Lodge

Preconference SymposiumPreconference Symposium17 March 200817 March 2008

State-of-the-Art State-of-the-Art TechnologicalTechnological

Developments in Developments in ConcreteConcrete

“Nanotechnology Applied to Bulk Concrete”

Barry E. ScheetzBarry E. ScheetzDepartment of Civil and Environmental

EngineeringThe Pennsylvania State University

Presentation Outline

*Who first defined nano-?•Where are we using nano-stuff?•Why the big deal with nano-?Why the big deal with nano-?•What exactly is a nano?What exactly is a nano?*How does this work in bulk concrete?*How does this work in bulk concrete?**The future of nanotechnology and bulk concrete?

The term "nanotechnology" was first defined by Tokyo Science University, Norio Taniguchi in a 1974 paper (N. Taniguchi, "On the Basic Concept of 'Nano-Technology',"

Who first defined nano-?

Medicinecell imagingcancer therapy --- contact agentsdrug-delivery vehicles

Catalysisfuel cellscatalytic convertersphotocatalytic devices

Where are we using nano-stuff?

Cosmeticssunscreens

Textileswater and stain repellentwrinkle-feeinvisibility coat – military

Opticsscratch resistant coatings

Foodsanti-microbial packaging

Vehicle manufacturinghard coatings for wear resistance

Electronicsquantum dotssemiconductors

Why the big deal with nano-Why the big deal with nano-??

The nano-materials behave nonlinearly i.e. hard materials become ‘super’ hard

At the scale of a cluster of a few unit cells [nanometers], conventional ideas of structure-property relationships no long hold.

What exactly is a nano?What exactly is a nano?What exactly is a nano?What exactly is a nano?

1 grain of sand in 200 lbs

A billionth of a meter10-9

Nanotechnology and bulk concreteNanotechnology and bulk concrete practicespractices

In 1974 when Dr. Taniguchi first defined ‘nano-,’nano-seeding of portland cement concrete wasbeing practiced in Philadelphia for 2 years.

In 1974, it was being practiced in Europe forabout 30 years.

It took almost 20 more year, until 1995, beforeI was able to recognize the phenomena

Humana Inc. Headquarters Building – Louisville, Kentucky - 1983

Applications of this technologyApplications of this technology

*basement structure had to withstandhydraulic head of 16 feet

Philadelphia International Airport Parking Garages -1976

*repeated exposure to salt

Camden Aquarium Penguin Exhibit –

Camden, NJ - 1998

* Shotcrete application for fast and easy construction of water channels

*water treatment facilitiesNSF Standard 61 approved

How does this work in bulk concrete?How does this work in bulk concrete?

nano

nano

nano

Principal Mineralogical Components Principal Mineralogical Components Of Portland CementOf Portland Cement

•tri-calcium silicate [Ctri-calcium silicate [C33S]S]•di-calcium silicate [Cdi-calcium silicate [C22S]S]•tri-calcium aluminate [Ctri-calcium aluminate [C33A]A]•tetra-calcium aluminoferrite [Ctetra-calcium aluminoferrite [C22AF]AF]

C-S-H65.0%

CH20.0%

Ettringite10.0%

Unhydrated5.0%

Mineralogical Composition of HydratedMineralogical Composition of HydratedPortland CementPortland Cement

C3S + H2O C-S-H + CH

3CaO3CaO . . SiO SiO22 + (3+ + (3+m-nm-n)H)H22O O

nnCaOCaO..SiOSiO22..mmHH22O + (3-O + (3-nn)Ca(OH))Ca(OH)22

QQ

tt

Hydration of CHydration of C33AA

Induction PeriodInduction Period

Hydration of CHydration of C33SS

Hydration ofHydration ofCC22SS

Heat of Hydration of Portland CementHeat of Hydration of Portland Cement

Solubility of CSolubility of C33S S

in Portland Cement Slurryin Portland Cement Slurry

0 10 20 30 40 50 60 70

time [minutes]

0

1

2

3

4

5

6

7

Sili

ca [

mm

/L]

Equilibrium saturationEquilibrium saturationcurvecurve

supersaturationsupersaturation

Point at which nucleation occuresPoint at which nucleation occuresin ordinary non-seeded systemsin ordinary non-seeded systems

On set of nucleation with the useOn set of nucleation with the useof nano-seedsof nano-seeds

Impact of Seeding of Heat of HydrationImpact of Seeding of Heat of Hydration

0

1

2

3

Time,hour5 10 150

P,mW

cement 0.5%

cement 1%

Cement control

Cement 2%

SEM image of AES seedsSEM image of AES seeds

5nm

TEM image of AES

Schematic vs. Actual Images of C-S-HSchematic vs. Actual Images of C-S-H

200 nm200 nm

3 nm3 nm

~ 10~ 102323 seeds get added to seeds get added to 100 pounds of cement100 pounds of cement

100,000,000,000,000,000,000,000 : 100100,000,000,000,000,000,000,000 : 100

At recommended mass loadings of 1% by weightof cement in the concrete

Microstructure Microstructure withoutwithoutwithwith

Ca(OH)2

Individual hydratedcement grain

C-S-H65.0%

CH20.0%

Ettringite10.0%

Unhydrated5.0%

Large Proportion Large Proportion of Hydrationof Hydration

Products are Products are DeleteriousDeleterious

In unmodifiedIn unmodifiedPortlandPortlandCementCement

ConcreteConcrete

Electron Backscatter Images of Electron Backscatter Images of Ohio DOT bridgeOhio DOT bridge

Benefits of microstructure Benefits of microstructure control on the nanometer control on the nanometer

scalescale*Uniformity of the microsturcture*Uniformity of the microsturcture

>minimize stress concentrators>minimize stress concentrators>homogeneous bonding to filler >homogeneous bonding to filler

materialsmaterials*Reduction in critical flaw size*Reduction in critical flaw size KIC = Y σ (c)1/2

by the dispersion of by the dispersion of portlanditeportlandite

The primary function of the admixture is for the manufacture of

“watertight concrete and reinforcement corrosion protection.”

The MaterialThe Material

Ref: CIAS Report: 02-1

* compositionally it is an Alkaline Earth Silicate [AES] C-S-H

* it is sold in the form of a liquid

* dosage rate is 1% by weight of portland cement [equivalent to 400 ppm concrete]

WaterWater PermeabilityPermeability PerformancePerformance

Raw dataRaw dataPA turnpikePA turnpike

0.2 microdarcys0.2 microdarcys**

<1 nanodarcy<1 nanodarcy* sample taken from* sample taken fromsection that was notsection that was notcompromised bycompromised by deteriorationdeterioration

ASTM C 441ASTM C 441

w/ow/o

ww

Carbon DioxideCarbon Dioxide PenetrationPenetration

After 25 YearsAfter 25 Years25.4mm

“The Big House”University of Michigan StadiumUniversity of Michigan Stadium

* 460,000 sq.ft. repair to risers and tread surface area;* depth of replacement: 1/8” to 6”* 1972 to 1979

Repair method:Repair method:alkaline earth silicatealkaline earth silicatemodified repair mortarmodified repair mortar

Ref: Concrete International (Sept 1980)

Repaired surfaces --- 25 + years later.

Melting snow

20011972

Damage to riser and tread area

2001

* cast the same day at the same pre-cast facility

* mix designs ‘identical’ > one had AES > one had corrosion inhibitor

* seven structures in 5 mile stretch; 6 control and 1 with admixture* AES modified placed 1973; 6 control placed 1974

Pennsylvania Turnpike

0

50

100

150

200

250

Det

erio

rati

on

Ind

exS

um o

f lin

ear

ft. c

rack

ing,

sq.

ft. s

pallin

g an

d sq

. ft.

dala

min

atio

ns

Control Concrete (average of 6) Concrete w ith Admixture

Cracking (lin. ft.)

Spalling (sq. ft.)Delaminations (sq. ft.)

Wiss, Janney & Elstner Evaluation of PA Turnpike BridgeWiss, Janney & Elstner Evaluation of PA Turnpike BridgeDeteriorationDeterioration

The MechanismThe Mechanism

A

B

MIP results of pore size distributionMIP results of pore size distributionin slag-OPC blended concretein slag-OPC blended concrete

Total porosity9.2%

Total porosity14.5%

78.9%

91.4%

6 sack concrete mix50% OPC/50% slag

W/C = 0.43Cured 28 days

6 sack concrete mix50% OPC/50% slag

W/C = 0.43Cured 28 days

With AES

Water flow will follow the path of least resistance. Tortuosity is a ratio of the “actual”length of the flow path, which often is very sinuous and the shortest

distances between the end points of the flow.

Lmin

Lmax

Lintermediate

Case #1 - ordinary concrete

T = Lmin

Case #2 - mineraladmixture concreteT = Lintermediate/Lmin

Case #3 AESconcrete

T = Lmax/Lmin

Sheriann Ki Sun BurnhamTortuosity #9

3-3 composite3-3 composite

3D solid matrix3D solid matrix andand3D void structure3D void structure

TortuosityTortuosity

DDeffeff.. = = DDintint

DDeff. eff. == effective diffusion coefficienteffective diffusion coefficient

DDintint = intrinsic diffusion coefficient = intrinsic diffusion coefficient

= porosityporosity = tortuosity factortortuosity factor

= = 22 / c / c

2 2 = tortuosity= tortuosity

C = constricivityC = constricivity

The future of nanotechnology and bulk concrete?

> Nano-materials must be incorporated into cementitious systems in an aqueous media.> The result is that small mass loadings of very small seed results in extremely large numbers of individual particles.

> At conventional low levels of addition, there is not enough material added to impact the physical properties

Future continued:

> Distributing seed uniformly throughout a concrete body therefore controls the ‘entire’ volume of the concrete body

> calcium carbonate is reported to enhance the mechanical strength of pastes made with 100,000 to 200,000ppm addition of nano-particles

Future continued:

> At concentrations greater than 100,000ppm [ a situation not hitherto examined]

these seeds offer a significant potential, when used with a system such as DSP cement, to further enhance densification resulting in enhanced mechanical properties