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

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

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 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  Typical Clinker Composition CaO (67%); SiO 2 (22%); Al 2 O 3 (5%); Fe 2 O 3 (3%)  Major Phases - Alite (50-70%): C 3 S (incorporating Mg 2+, Al 3+, Fe 3+ ) - Belite (15-30%):  C 2 S (incorporating foreign ions) - Aluminate phases (5-10%): C 3 A (Si 4+, Fe 3+, Na +, K + ) - Ferrite phases (5-15%): C 4 AF (variation in Al/Fe ratio, incorporation of foreign ions) C=CaO, S=SiO 2, A=Al 2 O 3, F=Fe 2 O 3 Interaction of admixtures with the major phases and their hydrates influence the rationale for use of controlled release technology NOTE

Major Cement Phases – Reactions with Water  2[3CaO.SiO 2 ]+7H 2 O  3CaO.2SiO 2.4H 2 O +3Ca(OH) 2 (C-S-H)  2[2CaO.SiO 2 ]+5H 2 O  3CaO.2SiO 2.4H 2 O+Ca(OH) 2 (C-S-H)  2[C 3 A]+21H  C 4 AH 13 +C 2 AH 8 C 4 AH 13 +C 2 AH 8  2C 3 AH 6 +9H  [C 4 AF]+16H  C 4 (A,F)H 8 [C 4 AF] + 16H  C 4 (A,F)H 13 + (A,F)H 3 Factors affecting the formation of C-S-H contribute to the rationale for controlled release technology NOTE C-S-H

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 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, L. Raki et al.: de-intercalation of layered double hydroxides to control loss of workability in cement-based materials US. Patent Applic 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 EP , US. Patent , 1994.

Chemical Admixtures in Concrete  Water reducers and retarders (eg. Ca, Na or NH 4 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)

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  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 Thickness 0.48nm Gallery Height OH M 2+, M 3+ OH Metal Cation Hydroxide Ion Layered (L) Double (D) Hydroxides(Hs) [ M(II) 1-x M(III) x (OH) 2 ] [ A n- x/n, mH 2 O ] 2 < 1-x/x < 5 d 001

Structure Layered Double Hydroxide and Hydrocalumite [ M(II) 1-x M(III) x (OH) 2 ] [ A n- x/n, mH 2 O ] 2 < 1-x/x < 5 LDH HC Brucite-type sheets Portlandite-type sheets V. Rives. Materials Chemistry and Physics 75 (2002), 19Rousselot et al. Journal of Solid State Chemistry, 167 (2002), 137

Anions Approach CO 3 2- and NO nm C= 0.82nm C=1.33nm C=2.18nm Note: H 2 O Molecules have been omitted Intercalation De-intercalation NBA 2NS

Synthesis of a CaAl-LDH Co-precipitation Technique  Co-precipitation of corresponding metal nitrate salts at room temperature: Prepare soln.: 0.28 moles Ca(NO 3 ) 2.4H 2 O 0.12 moles Al(NO 3 ) 3.9H 2 O 320 ml distilled water Add dropwise to soln.: 0.6 moles NaOH 0.4 moles NaNO 3  pH 9.6 Heat: 16h, 65 °C, Stirring Collect and filter precipitate, wash dry 16h at 100 °C in vacuum

Synthesis of a CaAl-LDH Intercalation of Organic Molecules 2.5g CaAl-LDH dispersed in 250ml of 0.1M aqueous soln of organic salts. Interact under nitrogen with stirring at °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-LDH Organic Intercalates – Cement Science

Analysis of LDH’s XRD

LDH Nanocomposites

Analysis of LDH’s FTIR

Inorganic Host LDH-CaAl Analysis of LDH’s SEM

Nanocomposite CaAl/NBA Analysis of LDH’s SEM

De-intercalation (0.1M NaOH) Admixture Delivery – De-intercalation Nitrobenzoic Acid XRD (A) + (A)

De-intercalation (0.2M NaOH) XRD Admixture Delivery – De-intercalation Nitrobenzoic Acid

Admixture Delivery – De-intercalation Nitrobenzoic Acid FTIR

Inorganic host Organic-inorganic Composite Admixture Delivery – De-intercalation Nitrobenzoic Acid 27 Al MAS NMR

Selected Properties Conduction Calorimetry C 3 S (w/s=0.50)

Selected Properties Conduction Calorimetry C 3 S (w/s=0.50)

Selected Properties Minislump

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

 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 Remarks

Thank You Merci