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Controlled Release of Chemical Admixtures Controlled Release of Chemical Admixtures in Cement-Based Materialsin Cement-Based Materials
L. Raki and J. J. Beaudoin
Princeton University
April 14, 2008
OutlineOutline
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
OutlineOutline
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 ChallengeOur 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 CementPortland 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%): C2S (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 and their hydrates influence the rationale for use of
controlled release technologyNO
TE
Major Cement Phases – Reactions with WaterMajor 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
Factors affecting the formation of C-S-H contribute to the rationale for controlled release technologyNO
TE
C-S-H
Controlled Release of Admixtures in Controlled Release of Admixtures in Cement Systems – Relevant LiteratureCement 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 Controlled Release of Admixtures in Cement Systems – Relevant LiteratureCement 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 ConcreteChemical 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--naphthalene sulfonate
- poly-melamine sulfonates
- carboxylated polymers (polyacrylates or polycarboxylates)
FocusFocus
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 Controlled release of chemicals in various media – a multidisciplinary conceptmedia – 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 Thickness0.48nm
Gallery Height
OH
M2+, M3+
OH
Metal Cation
Hydroxide Ion
Layered (L) Double (D) Hydroxides(Hs)Layered (L) Double (D) Hydroxides(Hs)
[ M(II)1-x M(III)x (OH)2 ] [ An-x/n , mH2O ] 2 < 1-x/x < 5
d001
Structure Structure Layered Double Hydroxide and HydrocalumiteLayered Double Hydroxide and Hydrocalumite
[ M(II)1-x M(III)x (OH)2 ] [ An-x/n , mH2O ] 2 < 1-x/x < 5
LDH HC
Brucite-type sheets
Portlandite-type sheets
V. Rives. Materials Chemistry and Physics 75 (2002), 19 Rousselot et al. Journal of Solid State Chemistry, 167 (2002), 137
AnionsAnions
Approach Approach
CO32- and NO3
-
0.48nm
C= 0.82nm
C=1.33nm
C=2.18nm
Note:H2O Molecules have been omitted
Intercalation
IntercalationDe-intercalation
De-intercalation
NBA
2NS
Synthesis of a CaAl-LDHSynthesis of a CaAl-LDHCo-precipitation TechniqueCo-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-LDHSynthesis of a CaAl-LDHIntercalation of Organic MoleculesIntercalation 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
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-LDHSynthesis of a CaAl-LDHOrganic Intercalates – Cement ScienceOrganic Intercalates – Cement Science
Analysis of LDH’sAnalysis of LDH’sXRDXRD
10 20 30 40 50
2-Theta(°)
0
500
1000
1500
2000
Inte
nsity
(Cou
nts)
CaAlNBA LDH
CaAlLDH
CaAl26NS LDH
CaAl2NS LDH
0.86 nm
1.33 nm
1.73 nm
2.18 nm
LDH NanocompositesLDH Nanocomposites
Analysis of LDH’sAnalysis of LDH’sFTIRFTIR
Inorganic Host
LDH-CaAl
Analysis of LDH’sAnalysis of LDH’sSEMSEM
Nanocomposite
CaAl/NBA
Analysis of LDH’sAnalysis of LDH’sSEMSEM
De-intercalation (0.1M NaOH)
10 20 30 40 50 60
2-Theta(°)
0
50
100
150
200
250
300
350
400
450
500
Inte
nsity(C
ou
nts
)
[lr053.raw] C2ANBAssept
C2ANBA
Deint15
Deint30
Deint60
Deint120
Deint180
Admixture Delivery – De-intercalationAdmixture Delivery – De-intercalationNitrobenzoic AcidNitrobenzoic Acid
XRD
(A)
+ (A)
De-intercalation (0.2M NaOH)
10 20 30 40 50 60
2-Theta(°)
0
250
500
750
1000
Inte
nsi
ty(C
ou
nts
)
[lr053.raw] C2ANBAssept
C2ANBA
Deint15
Deint30
Deint60
Deint120
Deint180d=0.76 nm
XRD
Admixture Delivery – De-intercalationAdmixture Delivery – De-intercalationNitrobenzoic AcidNitrobenzoic Acid
0 min 15 min 30 min 60 min
990016002150 1400 1200
Admixture Delivery – De-intercalationAdmixture Delivery – De-intercalationNitrobenzoic AcidNitrobenzoic Acid
FTIR
-100-50050100
0 min 15 min 30 min
Inorganic host
Organic-inorganic
Composite
Admixture Delivery – De-intercalationAdmixture Delivery – De-intercalationNitrobenzoic AcidNitrobenzoic Acid
27Al MAS NMR
0
0.5
1
1.5
2
2.5
3
0 5 10 15 20 25 30
Time in Hours
Heat
Ou
tpu
t
Control
Control +0.06 g Composite
Control + 0.06 g Accelerator (NBA)
Control + 0.24 g Composite
Control + 0.24 g Accelerator (NBA)
Selected PropertiesSelected PropertiesConduction CalorimetryConduction Calorimetry
C3 S (w/s=0.50)
0
1
2
3
4
0 4 8 12 16 20 24 28
Time, hours
Hea
t ou
pu
t
Control
Control + 0.06g Composite
Control + 0.06g Superplasticizer (SNF)
Control + 0.24g Composite
Control + 0.24g Superplasticizer (SNF)
Selected PropertiesSelected PropertiesConduction CalorimetryConduction Calorimetry
C3 S (w/s=0.50)
Mini-Slump (paste) vs timeW/C=0.50
20
40
60
80
100
120
140
160
0 60 120 180 240 300 360
Time, minutes
Slu
mp
diam
eter
, m
m
0.3% Disal
2.4% CaDisal
Selected PropertiesSelected PropertiesMinislumpMinislump
Mini-slump (mortar) vs timeW/C=0.59
70
80
90
100
110
120
0 60 120 180 240
Time, minutes
Slu
mp
dia
me
ter,
mm
.
0.3% Disal
3.6% CaDisal
Selected PropertiesSelected PropertiesMinislumpMinislump
Work in ProgressWork 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 RemarksConcluding Remarks
Thank You Thank You
MerciMerci