Controlled release of chemical admixtures in cement based materials
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Princeton University April 14, 2008. Controlled Release of Chemical Admixtures in Cement-Based Materials. L. Raki and J. J. Beaudoin. Outline. Our challenge Portland cement and its major phases Basic reactions of cement phases Controlled release-relevant literature

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Princeton UniversityApril 14, 2008

Controlled Release of Chemical Admixtures in Cement-Based Materials

L. Raki and J. J. Beaudoin


Outline l.jpg
Outline

  • 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


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Outline

  • 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


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Our 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


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Portland 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%): bC2S (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

NOTE

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


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Major 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

C-S-H

NOTE

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


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Controlled Release of Admixtures in Cement 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


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Controlled Release of Admixtures in Cement 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.


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Chemical Admixtures in Concrete Relevant Literature

  • 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-b-naphthalene sulfonate

    - poly-melamine sulfonates

    - carboxylated polymers (polyacrylates or polycarboxylates)


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Focus Relevant Literature

  • 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


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Controlled release of chemicals in various media – 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


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

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

Hydroxide Ion

Metal Cation

OH

Layer Thickness0.48nm

M2+, M3+

OH

d001

Gallery Height


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Structure multidisciplinary conceptLayered Double Hydroxide and Hydrocalumite

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

LDH

HC

Portlandite-type sheets

Brucite-type sheets

V. Rives. Materials Chemistry and Physics 75 (2002), 19

Rousselot et al. Journal of Solid State Chemistry, 167 (2002), 137


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Approach multidisciplinary concept

NBA

De-intercalation

Intercalation

C=1.33nm

Anions

CO32- and NO3-

0.48nm

C= 0.82nm

2NS

C=2.18nm

De-intercalation

Intercalation

Note:

H2O Molecules have been omitted


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Synthesis of a CaAl-LDH multidisciplinary conceptCo-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


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Synthesis of a CaAl-LDH multidisciplinary conceptIntercalation 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


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Synthesis of a CaAl-LDH multidisciplinary conceptOrganic Intercalates – Cement Science

  • The following organic intercalates were used to form the nanocomposites:

    • 2,6-naphthalene disulfonic acid

    • Naphtalene-2-sulfonic acid

    • Nitrobenzoic acid

    • Disal (SNF superplasticizer)


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Analysis of LDH’s multidisciplinary conceptXRD


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LDH Nanocomposites multidisciplinary concept


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Analysis of LDH’s multidisciplinary conceptFTIR


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Analysis of LDH’s multidisciplinary conceptSEM

Inorganic Host

LDH-CaAl


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Analysis of LDH’s multidisciplinary conceptSEM

Nanocomposite

CaAl/NBA


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Admixture Delivery – De-intercalation multidisciplinary conceptNitrobenzoic Acid

XRD

De-intercalation (0.1M NaOH)

+ (A)

(A)


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Admixture Delivery – De-intercalation multidisciplinary conceptNitrobenzoic Acid

XRD

De-intercalation (0.2M NaOH)


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Admixture Delivery – De-intercalation multidisciplinary conceptNitrobenzoic Acid

FTIR

2150

1600

9900

1400

1200


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Admixture Delivery – De-intercalation multidisciplinary conceptNitrobenzoic Acid

27Al MAS NMR

Organic-inorganic

Composite

Inorganic host


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Selected Properties multidisciplinary conceptConduction Calorimetry

C3 S (w/s=0.50)


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Selected Properties multidisciplinary conceptConduction Calorimetry

C3 S (w/s=0.50)


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Selected Properties multidisciplinary conceptMinislump


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Selected Properties multidisciplinary conceptMinislump


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Work in Progress multidisciplinary concept

  • 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


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Concluding Remarks multidisciplinary concept

  • 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


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Thank You multidisciplinary concept

Merci


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