Controlled Release of Chemical Admixtures in Cement-Based Materials L. Raki and J. J. Beaudoin...

Controlled Release of Chemical Admixtures Controlled Release of Chemical Admixtures in Cement-Based Materialsin Cement-Based Materials

L. Raki and J. J. Beaudoin

Princeton University

April 14, 2008

OutlineOutline

Our challenge Portland cement and its major phases Basic reactions of cement phases Controlled release-relevant literature Chemical admixtures in concrete CR- a multidisciplinary concept Layered Double Hydroxides

OutlineOutline

Approach Synthesis and analysis of LDHs Admixture delivery – de-intercalation Selected properties of cement paste and

mortar containing CR additives Work in progress Concluding remarks

Our ChallengeOur Challenge

Develop new technologies and innovative solutions for delivery of admixtures

in cement systems

+Use of nanotechnology approach

Synthesis of novel smart cement-based materials - CR of chemicals

Portland CementPortland Cement

Typical Clinker Composition

CaO (67%); SiO2 (22%); Al2O3 (5%); Fe2O3 (3%)

Major Phases- Alite (50-70%): C3S (incorporating Mg2+, Al3+, Fe3+)

- Belite (15-30%): C2S (incorporating foreign ions)

- Aluminate phases (5-10%): C3A (Si4+, Fe3+, Na+, K+)

- Ferrite phases (5-15%): C4AF (variation in Al/Fe ratio, incorporation of foreign ions)

C=CaO, S=SiO2, A=Al2O3, F=Fe2O3

Interaction of admixtures with the major phases and their hydrates influence the rationale for use of

controlled release technologyNO

TE

Major Cement Phases – Reactions with WaterMajor Cement Phases – Reactions with Water

2[3CaO.SiO2]+7H2O 3CaO.2SiO2.4H2O +3Ca(OH)2 (C-S-H)

2[2CaO.SiO2]+5H2O 3CaO.2SiO2.4H2O+Ca(OH)2 (C-S-H)

2[C3A]+21H C4AH13+C2AH8

C4AH13+C2AH8 2C3AH6+9H [C4AF]+16H C4(A,F)H8

[C4AF] + 16H C4(A,F)H13 + (A,F)H3

Factors affecting the formation of C-S-H contribute to the rationale for controlled release technologyNO

TE

C-S-H

Controlled Release of Admixtures in Controlled Release of Admixtures in Cement Systems – Relevant LiteratureCement Systems – Relevant Literature

‘Encapsulation’C. M. Dry: coated hollow polypropylene fibers used to disperse a corrosion inhibitor (calcium nitrate); Cem. Concr. Res. 28(8),1133, 1998

: Porous aggregate containing antifreeze; Ceram. Trans. v16, 729, 1991

B. R. Reddy et al. : Oil well treating fluids encapsulated in porous solid materials eg. Metal oxides containing accelerators, retarders, dispersants. US. Patent 6, 209, 646, 2001

Controlled Release of Admixtures in Controlled Release of Admixtures in Cement Systems – Relevant LiteratureCement Systems – Relevant Literature

‘Intercalation - De-Intercalation’H. Tatematsu et al. : inorganic and organic cation and anion exchangers eg. Calcium substituted zeolite and hydrocalumite. Exchange of alkali and chloride ion inhibit alkali-aggregate reaction and corrosion of rebar. US. Patent 5,435, 848, 1995.

L. Raki et al.: de-intercalation of layered double hydroxides to control loss of workability in cement-based materials

US. Patent Applic. 0022916 A1, 2007

‘In situ chemical reactions’K. Hambae et al. : addition of substances which hydrolyze under alkaline conditions (pH=12.5) to form cement dispersing agents.

EU Patent EP0402319, 1994. US. Patent 5350450, 1994.

Chemical Admixtures in ConcreteChemical Admixtures in Concrete

Water reducers and retarders(eg. Ca, Na or NH4 salts of lignosulfonic acids)

Accelerators(eg. Alkali hydroxides, silicates, calcium formate, calcium nitrate, sodium chloride)

Superplasticizers- reduce water content

- maintain workability at low water-cement ratio

Types:

- poly--naphthalene sulfonate

- poly-melamine sulfonates

- carboxylated polymers (polyacrylates or polycarboxylates)

FocusFocus

The focus of this presentation will be on controlled release (CR) of superplasticizers (SP)

CR can mitigate the effects of preferential adsorption of SP by aluminate phases

CR can minimize workability loss and extend the practical range of on-site delivery

Controlled release of chemicals in various Controlled release of chemicals in various media – a multidisciplinary conceptmedia – a multidisciplinary concept

Anion exchange by modifying LDH-type structures:• Cement-additive for time controlled delivery of

superplasticizers, corrosion inhibitors and other functional admixtures

Other disciplines utilizing LDH’s

• Delivery carrier for drugs

• Gene reservoirs

• CR of plant growth regulators

Layer Thickness0.48nm

Gallery Height

OH

M2+, M3+

OH

Metal Cation

Hydroxide Ion

Layered (L) Double (D) Hydroxides(Hs)Layered (L) Double (D) Hydroxides(Hs)

[ M(II)1-x M(III)x (OH)2 ] [ An-x/n , mH2O ] 2 < 1-x/x < 5

d001

Structure Structure Layered Double Hydroxide and HydrocalumiteLayered Double Hydroxide and Hydrocalumite

[ M(II)1-x M(III)x (OH)2 ] [ An-x/n , mH2O ] 2 < 1-x/x < 5

LDH HC

Brucite-type sheets

Portlandite-type sheets

V. Rives. Materials Chemistry and Physics 75 (2002), 19 Rousselot et al. Journal of Solid State Chemistry, 167 (2002), 137

AnionsAnions

Approach Approach

CO32- and NO3

-

0.48nm

C= 0.82nm

C=1.33nm

C=2.18nm

Note:H2O Molecules have been omitted

Intercalation

IntercalationDe-intercalation

De-intercalation

NBA

2NS

Synthesis of a CaAl-LDHSynthesis of a CaAl-LDHCo-precipitation TechniqueCo-precipitation Technique

Co-precipitation of corresponding metal nitrate salts at room temperature:• Prepare soln.: 0.28 moles Ca(NO3)2.4H2O

0.12 moles Al(NO3)3.9H2O

320 ml distilled water

• Add dropwise to soln.: 0.6 moles NaOH 0.4 moles NaNO3

pH 9.6

• Heat: 16h, 65 °C, Stirring

• Collect and filter precipitate, washdry 16h at 100 °C in vacuum

Synthesis of a CaAl-LDHSynthesis of a CaAl-LDHIntercalation of Organic MoleculesIntercalation of Organic Molecules

• 2.5g CaAl-LDH dispersed in 250ml of 0.1M aqueous soln of organic salts.

• Interact under nitrogen with stirring at 65-70 °C

• Filter, wash with distilled water and acetone, dry 4h at 100 °C

Intercalates include Disal (SNF) superplasticizer

The following organic intercalates were used to form the nanocomposites:

• 2,6-naphthalene disulfonic acid

• Naphtalene-2-sulfonic acid

• Nitrobenzoic acid

• Disal (SNF superplasticizer)

Synthesis of a CaAl-LDHSynthesis of a CaAl-LDHOrganic Intercalates – Cement ScienceOrganic Intercalates – Cement Science

Analysis of LDH’sAnalysis of LDH’sXRDXRD

10 20 30 40 50

2-Theta(°)

0

500

1000

1500

2000

Inte

nsity

(Cou

nts)

CaAlNBA LDH

CaAlLDH

CaAl26NS LDH

CaAl2NS LDH

0.86 nm

1.33 nm

1.73 nm

2.18 nm

LDH NanocompositesLDH Nanocomposites

Analysis of LDH’sAnalysis of LDH’sFTIRFTIR

Inorganic Host

LDH-CaAl

Analysis of LDH’sAnalysis of LDH’sSEMSEM

Nanocomposite

CaAl/NBA

Analysis of LDH’sAnalysis of LDH’sSEMSEM

De-intercalation (0.1M NaOH)

10 20 30 40 50 60

2-Theta(°)

0

50

100

150

200

250

300

350

400

450

500

Inte

nsity(C

ou

nts

)

[lr053.raw] C2ANBAssept

C2ANBA

Deint15

Deint30

Deint60

Deint120

Deint180

Admixture Delivery – De-intercalationAdmixture Delivery – De-intercalationNitrobenzoic AcidNitrobenzoic Acid

XRD

(A)

+ (A)

De-intercalation (0.2M NaOH)

10 20 30 40 50 60

2-Theta(°)

0

250

500

750

1000

Inte

nsi

ty(C

ou

nts

)

[lr053.raw] C2ANBAssept

C2ANBA

Deint15

Deint30

Deint60

Deint120

Deint180d=0.76 nm

XRD


0 min 15 min 30 min 60 min

990016002150 1400 1200


FTIR

-100-50050100

0 min 15 min 30 min

Inorganic host

Organic-inorganic

Composite


27Al MAS NMR

0

0.5

1

1.5

2

2.5

3

0 5 10 15 20 25 30

Time in Hours

Heat

Ou

tpu

t

Control

Control +0.06 g Composite

Control + 0.06 g Accelerator (NBA)

Control + 0.24 g Composite

Control + 0.24 g Accelerator (NBA)

Selected PropertiesSelected PropertiesConduction CalorimetryConduction Calorimetry

C3 S (w/s=0.50)

0

1

2

3

4

0 4 8 12 16 20 24 28

Time, hours

Hea

t ou

pu

t

Control

Control + 0.06g Composite

Control + 0.06g Superplasticizer (SNF)

Control + 0.24g Composite

Control + 0.24g Superplasticizer (SNF)

Selected PropertiesSelected PropertiesConduction CalorimetryConduction Calorimetry

C3 S (w/s=0.50)

Mini-Slump (paste) vs timeW/C=0.50

20

40

60

80

100

120

140

160

0 60 120 180 240 300 360

Time, minutes

Slu

mp

diam

eter

, m

m

0.3% Disal

2.4% CaDisal

Selected PropertiesSelected PropertiesMinislumpMinislump

Mini-slump (mortar) vs timeW/C=0.59

70

80

90

100

110

120

0 60 120 180 240

Time, minutes

Slu

mp

dia

me

ter,

mm

.

0.3% Disal

3.6% CaDisal

Selected PropertiesSelected PropertiesMinislumpMinislump

Work in ProgressWork in Progress

Development of new friendly inexpensive method for large scale production of CR composites

Development of CR composites containing various types of superplasticizer, citric acid and salicylic acid.

Physical/mechanical tests on mortar and concrete

Effect of CR nanocomposites on hydration characteristics of cement systems

Nano LDH composites have the potential to provide improved controlled release delivery of chemical admixtures in cement-based materials

LDH-based technologies are versatile with the potential to utilize through the intercalation mechanism process numerous different admixtures in the same host matrix

Controlled-release delivery of all types of superplasticizers in concrete is a promising developing technology

Concluding RemarksConcluding Remarks

Thank You Thank You

MerciMerci

Controlled Release of Chemical Admixtures in Cement-Based Materials L. Raki and J. J. Beaudoin...

Documents

Transcript of Controlled Release of Chemical Admixtures in Cement-Based Materials L. Raki and J. J. Beaudoin...