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20/10/2015
1
ROLE OF DIFFERENT SUPERPLASTICIZERS ON HYDRATED LIME PASTES AND MORTARS
Department of Chemistry and Soil Sciences,
Research Group on Inorganic Materials & Environment
UNIVERSITY OF NAVARRA
Duran, A., Navarro-Blasco, I., Pérez-Nicolás, M., Sirera, R., Fernández, J.M., Alvarez, J.I.
Beijing, October, 2015
Lime mortars + pozzolanic additives: hydraulic mortars
Nanosilica (NS) and metakaolin (MK) have been extensively used as SupplementaryCementitious Materials to improve the mechanical strength and to short the setting time ofair lime mortars.
Air lime mortars + pozzolanic add. + SUPERPLASTICIZERS
to gain a better understanding on the behavior of different SPs in lime-bearing pastes and mortars
AIM OF THIS WORK
Introduction
Lime mortars
• used in the Built Heritage over centuries• lime, usually air lime, as the binding material• renders, repair mortars and other mixes.
Materials
Air lime pastes and mortars were obtained by mixing
• Raw materials: Air lime (CL90) + limestone aggregate (1:3, w:w)
• Pozzolanic additives: Nanosilica or Metakaolin (6, 10 and 20% bwoc)
• Superplasticizers (0.5 and 1% bwoc):
two different polycarboxylate ethers (PCE1 and PCE2)
a polynaphthalene sulfonate-based (PNS) polymer
a lignosulfonate (LS)
Materials
500nm
4000 nm
Nanosilica Metakaolin
Superplasticizers molecules were studied by means of differenttechniques: SEC, FTIR-ATR, MALDI-TOFF mass spectrometry,anionic charge density, acid-base titration and elemental analysis.
TEM micrographs showing the particle size as well as the shapeof the pozzolanic additives
spherical shape, 500 m2/g card-house agglomerations, 20 m2/g
Results: Part 1
Elucidation of the molecular architecture of the SPs
Results: elucidation of the molecular architecture of the SPs
For PCE1:• wide range of signal intensities
(mass-to-charge – m/z – ratios)• position of the most intense
signal
Results of the MALDI-TOFF (Matrix Assisted Laser Desorption Ionization Time-of-Flight) analysis
Longer side chains and higher Mw thanthat of PCE2
Navarro-Blasco I, Pérez-Nicolás M, Fernández JM, Duran A, Sirera R, Alvarez JI. Assessment of the interaction of polycarboxylate superplasticizers in hydrated lime pastes modified with nanosilica or metakaolin as pozzolanic reactives. Constr Build Mater 2014;73:1-12.
20/10/2015
2
Results of the MALDI-TOFF (Matrix Assisted Laser Desorption Ionization Time-of-Flight) analysis
For PCE2:• narrower m/z distribution• lower m/z ratio
shorter side chains (with identical widthbetween the oligomer peaks) and lower Mw.
Results: elucidation of the molecular architecture of the SPs
Navarro-Blasco I, Pérez-Nicolás M, Fernández JM, Duran A, Sirera R, Alvarez JI. Assessment of the interaction of polycarboxylate superplasticizers in hydrated lime pastes modified with nanosilica or metakaolin as pozzolanic reactives. Constr Build Mater 2014;73:1-12.
PCE1
PCE2
For PCE1:• Lower anionic charge density• Larger Mw• Longer side length
For PCE2:• Higher anionic charge density• Lower Mw• Shorter side length
Short main backbone(low amount of COO- groups)
Longer main backbone(high amount of COO- groups)
Results: elucidation of the molecular architecture of the SPs
ACID-BASE TITRATION:• PNS 2.44 meq of anionic charge/g of polymer• LS 1.04 meq of anionic charge/g of polymer
LIGNOSULFONATE POLYNAPHTHALENESULFONATE
Results: elucidation of the molecular architecture of the SPs
SEC results: Mw
Results: Part 2
Fresh state properties of the air lime sampleswith superplasticizers
Results: fresh state properties
020
4060
80100
120140
160180
lime
lime+6%NS
lime+6%MK
lime+10%NS
lime+10%MK
lime+20%NS
lime+20%MK
Slump values of SP‐free samples
lime
lime+6%NS
lime+6%MK
lime+10%NS
lime+10%MK
lime+20%NS
lime+20%MK
Duran A, Navarro-Blasco I, Fernández JM, Alvarez JI. Long-term mechanical resistance and durability of air lime mortars with large additions of nanosilica. Constr Build Mater 2014;58:147-158.
Results: fresh state properties
Fernández JM, Duran A, Navarro-Blasco I, Lanas J, Sirera R, Alvarez JI. Influence of nanosilica and a polycarboxylate ether superplasticizer on theperformance of lime mortars. Cem Concr Res 2013 1;43(0):12-24
Particle size measurements (laser diffraction) Formation of largeagglomerations in
the presence of NS
20/10/2015
3
Results: fresh state properties
Fernández JM, Duran A, Navarro-Blasco I, Lanas J, Sirera R, Alvarez JI. Influence of nanosilica and a polycarboxylate ether superplasticizer on theperformance of lime mortars. Cem Concr Res 2013 1;43(0):12-24
Particle size measurements (laser diffraction)
Addition of PCE1
Disappearance of thelarge agglomerations
Disappearance of thelarge agglomerations
0 50 100 150 200 250 300
0.25%PCE1
0.50% PCE1
0.75% PCE1
0.25%PCE2
0.50% PCE2
0.75% PCE2
0.25% PNS
0.50% PNS
0.75% PNS
0.25% LS
0.50% LS
0.75% LS
Slump values of air lime samples
0.25%PCE1
0.50% PCE1
0.75% PCE1
0.25%PCE2
0.50% PCE2
0.75% PCE2
0.25% PNS
0.50% PNS
0.75% PNS
0.25% LS
0.50% LS
0.75% LS
Results: fresh state properties
Slump (mm)
0 50 100 150 200 250 300
0.25%PCE1
0.50% PCE1
0.75% PCE1
0.25%PCE2
0.50% PCE2
0.75% PCE2
0.25% PNS
0.50% PNS
0.75% PNS
0.25% LS
0.50% LS
0.75% LS
Slump values of samples with 10 wt.% of nanosilica
0.25%PCE1
0.50% PCE1
0.75% PCE1
0.25%PCE2
0.50% PCE2
0.75% PCE2
0.25% PNS
0.50% PNS
0.75% PNS
0.25% LS
0.50% LS
0.75% LS
142 144 146 148 150 152 154 156 158 160
0.25%PCE2
0.50% PCE2
0.75% PCE2
0.25% PNS
0.50% PNS
0.75% PNS
0.25% LS
0.50% LS
0.75% LS
Slump values of samples with 10 wt.% of nanosilica
0.25%PCE2
0.50% PCE2
0.75% PCE2
0.25% PNS
0.50% PNS
0.75% PNS
0.25% LS
0.50% LS
0.75% LS
Results: fresh state properties
0 50 100 150 200 250 300
0.25%PCE1
0.50% PCE1
0.75% PCE1
0.25%PCE2
0.50% PCE2
0.75% PCE2
0.25% PNS
0.50% PNS
0.75% PNS
0.25% LS
0.50% LS
0.75% LS
Slump values of samples with 10 wt.% of metakaolin
0.25%PCE1
0.50% PCE1
0.75% PCE1
0.25%PCE2
0.50% PCE2
0.75% PCE2
0.25% PNS
0.50% PNS
0.75% PNS
0.25% LS
0.50% LS
0.75% LS
Results: fresh state properties
Slump (mm)
0 20 40 60 80 100 120 140
120
140
160
180
200
220
240
260
280
300
Lime+PCE1 Lime+PCE2 Lime+PNS Lime+LS
Slu
mp
(mm
)
Increasing time after mixing of the fresh sample
Slump loss over the time: air lime pastes
Results: fresh state properties
PCE1 and LS showed the best slump retention abilities
0 20 40 60 80 100 120 140100
105
110
115
120
125
130
135
140
Lime+NS+PCE1 Lime+NS+PCE2 Lime+NS+PNS Lime+NS+LS
Slu
mp
(mm
)
Increasing time after mixing of the fresh sample
Slump loss over the time: air lime + nanosilica
Results: fresh state properties
20/10/2015
4
0 20 40 60 80 100 120 140120
140
160
180
200
220
240
260
280
300
320
340
Lime+MK+PCE1 Lime+MK+PCE2 Lime+MK+PNS Lime+MK+LS
Slu
mp
(mm
)
Increasing time after mixing of the fresh sample
Slump loss over the time: air lime + metakaolin
Results: fresh state properties
Adsorption isotherms of the PCEs assayed onto plain lime, lime-NS and lime-MK pastes (20 wt. % of pozzolanic additive) fitted acording to Freundlich model.
• PCE2 was adsorbed in a 3- to 4-fold when compared with PCE1, in plain air lime samples.
• high consumption of polycarboxylates in the presence of pozzolanic additives →high specific surface area (500 m2 g-1
nanosilica).
Results: fresh state properties
Langmuir and Freundlich adsorption parameters for both PNS and LS
Polynaphthalenesulfonate
Langmuir model Freundlich model
qm
(mg g-1)b
(dm3 mg-1)R2 K
(mg1-1/ndm3/ng-1)1/n R2
0%NS 52.08 1.07.10-4 0.831 1.29.10-2 0.859 0.998
6%NS 285.71 1.77.10-5 0.966 1.01.10-2 0.898 0.987
10%NS 3174.60 1.51.10-6 0.878 6.6.10-3 0.954 0.998
20%NS 3311.26 1.44.10 -6 0.450 4.9.10-3 0.996 1.000
Lignosulfonate
Langmuir model Freundlich model
qm
(mg g-1)b
(dm3 mg-1)R2 K
(mg1-1/ndm3/ng-1)1/n R2
0%NS 22.94 2.72.10-4 0.937 3.61.10-2 0.703 0.9556%NS 88.50 5.12.10-5 0.982 8.32.10-3 0.904 0.99810%NS 151.52 2.92.10-5 0.987 6.46.10-3 0.941 0.99920%NS 303.03 1.46.10-5 0.958 5.44.10-3 0.968 1.000
• High affinity of PNS for air lime particles• Large PNS adsorption onto solid particles• Great interaction of PNS with air lime media
Results: fresh state properties
Zeta potential of lime-NS and lime-MK pastes titrated with the PCEsuperplasticizers
Results: fresh state properties
• NS presented no ‘‘active’’ adsorption sites in connection with the C–S–H dispersion• The polymer adsorbed onto NS was not able to be adsorbed onto C–S–H
the overall zeta potential was modified to a limited extent for NS-bearing samples
Electric double layer
Si‐O‐
Si‐O‐
Si‐O‐
Si‐O‐
‐
‐‐
‐‐
+++
+
++
+
‐‐‐‐
‐
‐‐
‐‐‐
Particle surface
Shear plane
Si‐O‐
Si‐O‐
‐+
+
‐‐
‐
‐‐
Particle surface
Displaced shear plane
Si‐O‐
Si‐O‐‐
‐‐
‐
+++
+
+
‐
‐
‐ ‐
‐‐‐‐‐
‐Released anions
Perpendicular adsorption
Si‐O‐
Si‐O‐
‐+
+
‐‐
‐
‐‐
Particle surface
Displaced shear plane
Si‐O‐
Si‐O‐‐
‐‐
‐
+++
+
+
‐
‐‐
‐
‐Released anions
Flat adsorption
‐+
OH- anions
positive ions (e.g. Na+)
PCE2: worm-like polymer (largernegatively charged backbone)
PCE1: star-shaped polymer withnegatively charged backbone
The decrease in the zetapotential was caused inPCE1 by:
• the displacement of theshear plane of the outerHelmholtz layer owing tothe side chains of thecopolymers
Results: fresh state properties
The decrease in the zetapotential was caused inPCE2 by:
• the compensation of thepositive charge of theexternal layer of Ca2+ ionsby the negatively chargedpolycarboxylate units
Navarro-Blasco I, Pérez-Nicolás M, Fernández JM, Duran A, Sirera R, Alvarez JI. Assessment of the interaction of polycarboxylate superplasticizers in hydrated lime pastes modified withnanosilica or metakaolin as pozzolanic reactives. Constr Build Mater 2014;73:1-12.
• The PCEs attachment onto NS retarded the pozzolanic reactionbetween NS and Ca(OH)2
• the increasing amounts of superplasticizers caused strongerdelays in the setting time as compared with lime–MK samples.
Air lime pastes with 10 wt.% of NS Air lime pastes with 10wt.% of MK
• low adsorbed amounts of PCE1• better dispersing action of PCE1• requires lower dosage of plasticizing agent• steric hindrance was then the main action mechanism of these PCEs
Results: fresh state properties
0
300
600
900
1200
1500
0.00 0.25 0.50
Set
tin
g ti
me
(min
)
Increasing dosage of superplasticizer (%)
PCE 1
PCE 2
0
300
600
900
1200
1500
0.00 0.25 0.50
Set
tin
g ti
me
(min
)
Increasing dosage of superplasticizer (%)
PCE 1
PCE 2
20/10/2015
5
Zeta potential of lime-NS and lime-MK pastes titrated with PNS and LS
Results: fresh state properties
• PNS caused a sharper decrease in zeta potential• LS produced Ca2+ complex salts, with low adsorption onto portlandite or CSH• LS yielded higher slump values and presented a lower slump loss over the time
free LS molecules in the interstitial solution may act as a steric hindrance to preventparticles from agglomeration
Polynaphthalene sulfonate
• higher anionic charge density flat adsorption• linear shape
attached molecules surrounded by the growing carbonation/hydration products, yielding organo-mineral phases.
lower dispersion effectiveness , poor dispersion maintaining ability
Lignosulfonate• adsorption would be more perpendicular to the surface of the particles.
Results: fresh state properties
Results: Part 3
Influence of the SPs on the mechanical strengthand durability of the tested mortars
0
1
2
3
4
5
6
7
8
9
Controlgroup
20% NS 0% NS -0.5%SPP1
20%NS -0.5%SPP1
20%NS -1% SPP1
0% NS -0.5%SPP2
20%NS -0.5%SPP2
20%NS -1% SPP2
Co
mp
res
siv
e s
tre
ng
th (
N/m
m2
)
7
28
91
182
Results: impact on the mechanical strength
Compressive strength values of mortars with PCEs
Pore diameter (m)
dV
/dlo
gD
(mL
.g-1
)
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.001 0.01 0.1 1 10 100 1000
Pore diameter (m)
dV
/dlo
gD
(mL
.g-1
)
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.001 0.01 0.1 1 10 100 1000
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.001 0.01 0.1 1 10 100 1000
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.001 0.01 0.1 1 10 100 1000
Pore diameter (m)
dV
/dlo
gD
(mL
.g-1
)
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.001 0.01 0,1 1 10 100 1000
Pore diameter (m)
dV
/dlo
gD
(mL
.g-1
)
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.001 0.01 0,1 1 10 100 1000
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.001 0.01 0,1 1 10 100 1000
Macropores reduction
Mean pore size peak displacement
Total porosity reduction (AUC)
Control groupNS-PCE 0.5%NS-PCE 1.0%
Control groupNS-PCE 0.5%NS-PCE 1.0%, fixed mixing waterNS-PCE 1.0%
Results: impact on the mechanical strength
Alvarez JI, Fernández JM, Navarro-Blasco I, Duran A, Sirera R. Microstructural consequences of nanosilica addition on aerial lime binding materials: influence of different drying conditions. Mater Charact 2013;80:36-49
MIP analysis
values of mortars with PCE1
The textural characteristics (SEM) showed reducedporosity, and, on the other hand, the growing of calcitecrystals resulted in a more homogeneous and continuousmatrix, allowing the aggregate particles to be embedded.
Admixture-free mortar PCE-NS mortar
Results: impact on the mechanical strength
Fernández JM, Duran A, Navarro-Blasco I, Lanas J, Sirera R, Alvarez JI. Influence of nanosilica and a polycarboxylate ether superplasticizer on theperformance of lime mortars. Cem Concr Res 2013 1;43(0):12-24
SEM examination of mortars with PCE1
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6
Results: impact on the mechanical strength
Compressive strength values of mortars with PNS and LS
The micrograph of the LS-bearing sample depicts a wide area covered byC-S-H crystals
Results: impact on the mechanical strength
20% NS - 1% PNS 20% NS - 1% LS
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Control group
6% NS
10% NS
20% NS
0% NS ‐ 0.5% SPP1
6% NS ‐ 0.5% SPP1
10% NS ‐ 0.5% SPP1
20%NS ‐ 0.5% SPP1
0% NS ‐ 1% SPP1
6% NS ‐ 1% SPP1
10% NS ‐ 1% SPP1
20%NS ‐ 1% SPP1
0% NS ‐ 0.5% SPP2
6% NS ‐ 0.5% SPP2
10% NS ‐ 0.5% SPP2
20%NS ‐ 0.5% SPP2
0% NS ‐ 1% SPP2
6% NS ‐ 1% SPP2
10% NS ‐ 1% SPP2
20%NS ‐ 1% SPP2
F/T cycles
none totalmoderatescarce large
Decay degree
Specimens
freezing–thawing cycles durability
Results: impact on the mechanical strength
Duran A, Navarro-Blasco I, Fernández JM, Alvarez JI. Long-term mechanical resistance and durability of air lime mortars with large additions of nanosilica. Constr Build Mater 2014;58:147-158.
Conclusions
Conclusions
1) star-shaped polymer PCE1 as compared to PCE2 (worm like polymer)
• The lowest anionic charge density• The largest plasticizing effect in the assayed lime pastes• The lowest comsumption (low amount of adsorbed polymer)• Perpendicular adsorption• Steric hindrance• With metakaolin provided the best flowability in order to its use as grout• Better mechanical resistance and durability (freezing thawing cycles)
PCE1
PCE2
Conclusions
2) LS as compared to PNS
• More effective in increasing the fluidity of the samples• Able to form Ca2+ complexes• Large number of free LS molecules in the suspension• Strong steric effect• Favoured the formation of C-S-H
3) PNS
• Formation of organo-mineral phases that increased its consumption• Poor plasticizing performance• Low slump retention capacity• Electrostatic repulsion as the main dispersion mechanism