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Controlled Release of Chemical Admixtures in Cement-Based Materials

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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Controlled Release of Chemical Admixtures in Cement-Based Materials

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  1. Princeton UniversityApril 14, 2008 Controlled Release of Chemical Admixtures in Cement-Based Materials L. Raki and J. J. Beaudoin

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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.

  9. 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)

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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)

  18. Analysis of LDH’sXRD

  19. LDH Nanocomposites

  20. Analysis of LDH’sFTIR

  21. Analysis of LDH’sSEM Inorganic Host LDH-CaAl

  22. Analysis of LDH’sSEM Nanocomposite CaAl/NBA

  23. Admixture Delivery – De-intercalationNitrobenzoic Acid XRD De-intercalation (0.1M NaOH) + (A) (A)

  24. Admixture Delivery – De-intercalationNitrobenzoic Acid XRD De-intercalation (0.2M NaOH)

  25. Admixture Delivery – De-intercalationNitrobenzoic Acid FTIR 2150 1600 9900 1400 1200

  26. Admixture Delivery – De-intercalationNitrobenzoic Acid 27Al MAS NMR Organic-inorganic Composite Inorganic host

  27. Selected PropertiesConduction Calorimetry C3 S (w/s=0.50)

  28. Selected PropertiesConduction Calorimetry C3 S (w/s=0.50)

  29. Selected PropertiesMinislump

  30. Selected PropertiesMinislump

  31. 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

  32. 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

  33. Thank You Merci

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