Transcript Place Main Title Here

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)
NOTE
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 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
NOTE
[C4AF] + 16H  C4(A,F)H13 + (A,F)H3
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
M2+, M3+
Layer Thickness
0.48nm
Gallery Height
OH
d001
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
Brucite-type
sheets
V. Rives. Materials Chemistry and Physics 75 (2002), 19
HC
Portlandite-type
sheets
Rousselot et al. Journal of Solid State Chemistry, 167 (2002), 137
Approach
NBA
De-intercalation
Intercalation
C=1.33nm
CO32- and NO30.48nm
Anions
C= 0.82nm
2NS
C=2.18nm
Intercalation
Note:
H2O Molecules have been omitted
De-intercalation
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
2000
2.18 nm
CaAl2NS LDH
Intensity(Counts)
1500
1.73 nm
CaAl26NS LDH
1000
1.33 nm
CaAlNBA LDH
500
0.86 nm
CaAlLDH
0
10
20
30
2-Theta(°)
40
50
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)
[lr053.raw] C2ANBAssept
+ (A)
500
Deint180
450
400
Deint120
Intensity(Counts)
350
Deint60
300
250
Deint30
200
150
(A)
Deint15
100
50
C2ANBA
0
10
20
30
40
2-Theta(°)
50
60
Admixture Delivery – De-intercalation
Nitrobenzoic Acid
XRD
De-intercalation (0.2M NaOH)
[lr053.raw] C2ANBAssept
Intensity(Counts)
1000
750
d=0.76 nm
Deint180
500
Deint120
Deint60
250
Deint30
Deint15
C2ANBA
0
10
20
40
30
2-Theta(°)
50
60
Admixture Delivery – De-intercalation
Nitrobenzoic Acid
FTIR
0 min
2150
15 min
1600
30 min
1400
60 min
1200
9900
Admixture Delivery – De-intercalation
Nitrobenzoic Acid
27Al
MAS NMR
0 min
15 min
30 min
Organic-inorganic
Composite
Inorganic host
100
50
0
-50
-100
Selected Properties
Conduction Calorimetry
C3 S (w/s=0.50)
3
Control
Control +0.06 g Composite
Heat Output
2.5
Control + 0.06 g Accelerator (NBA)
Control + 0.24 g Composite
2
Control + 0.24 g Accelerator (NBA)
1.5
1
0.5
0
0
5
10
15
Time in Hours
20
25
30
Selected Properties
Conduction Calorimetry
C3 S (w/s=0.50)
Control
4
Control + 0.06g Composite
Control + 0.06g Superplasticizer (SNF)
Heat ouput
3
Control + 0.24g Composite
Control + 0.24g Superplasticizer (SNF)
2
1
0
0
4
8
12
16
Time, hours
20
24
28
Selected Properties
Minislump
Mini-Slump (paste) vs time
W/C=0.50
160
0.3% Disal
Slump diameter, mm
140
2.4% CaDisal
120
100
80
60
40
20
0
60
120
180
Time, minutes
240
300
360
Selected Properties
Minislump
Mini-slump (mortar) vs time
W/C=0.59
120
Slump diameter, mm .
0.3% Disal
110
3.6% CaDisal
100
90
80
70
0
60
120
Time, minutes
180
240
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