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
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%); 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
Interaction of admixtures with the major phases
NOTE
and their hydrates influence the rationale for use of
controlled release technology
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 C-S-H
[C4AF]+16H C4(A,F)H8
[C4AF] + 16H C4(A,F)H13 + (A,F)H3
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
‘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, 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
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
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
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 Thickness
M2+, M3+
0.48nm
OH
d001
Gallery Height
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
NBA
Intercalation De-intercalation
C=1.33nm
CO32- and NO3-
0.48nm
C= 0.82nm Anions
2NS
C=2.18nm
De-intercalation
Intercalation
Note:
H2O Molecules have been omitted
Synthesis of a CaAl-LDH
Co-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, 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 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
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
XRD
LDH Nanocomposites
Analysis of LDH’s
FTIR
Analysis of LDH’s
SEM
Inorganic Host
LDH-CaAl
Analysis of LDH’s
SEM
Nanocomposite
CaAl/NBA
Admixture Delivery – De-intercalation
Nitrobenzoic Acid
XRD
De-intercalation (0.1M NaOH)
+ (A)
(A)
Admixture Delivery – De-intercalation
Nitrobenzoic Acid
XRD
De-intercalation (0.2M NaOH)
Admixture Delivery – De-intercalation
Nitrobenzoic Acid
FTIR
2150 1600 1400 1200 9900
Admixture Delivery – De-intercalation
Nitrobenzoic Acid
27Al MAS NMR
Organic-inorganic
Composite
Inorganic host
Selected Properties
Conduction Calorimetry
C3 S (w/s=0.50)
Selected Properties
Conduction Calorimetry
C3 S (w/s=0.50)
Selected Properties
Minislump
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
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
Thank You
Merci