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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Presentation Transcript
outline
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
outline3
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
our challenge
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

portland cement
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

major cement phases reactions with water
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

controlled release of admixtures in cement systems relevant literature
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

controlled release of admixtures in cement systems relevant literature8
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.

chemical admixtures in concrete
Chemical 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-b-naphthalene sulfonate

- poly-melamine sulfonates

- carboxylated polymers (polyacrylates or polycarboxylates)

focus
Focus
  • 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 media a multidisciplinary concept
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
slide12

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

[ 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

structure layered double hydroxide and hydrocalumite
Structure Layered 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

approach
Approach

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

synthesis of a caal ldh co precipitation technique
Synthesis of a CaAl-LDHCo-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 ldh intercalation of organic molecules
Synthesis of a CaAl-LDHIntercalation 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

synthesis of a caal ldh organic intercalates cement science
Synthesis of a CaAl-LDHOrganic 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)
analysis of ldh s sem
Analysis of LDH’sSEM

Inorganic Host

LDH-CaAl

analysis of ldh s sem22
Analysis of LDH’sSEM

Nanocomposite

CaAl/NBA

admixture delivery de intercalation nitrobenzoic acid
Admixture Delivery – De-intercalationNitrobenzoic Acid

XRD

De-intercalation (0.1M NaOH)

+ (A)

(A)

admixture delivery de intercalation nitrobenzoic acid26
Admixture Delivery – De-intercalationNitrobenzoic Acid

27Al MAS NMR

Organic-inorganic

Composite

Inorganic host

work in progress
Work 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
slide32

Concluding Remarks

  • 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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