role of different superplasticizers on hydrated lime...

20/10/2015

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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.

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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.


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)


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


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.


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

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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


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


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


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


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

)


Slump loss over the time: air lime + nanosilica


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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

)


Slump loss over the time: air lime + metakaolin


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).


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


Zeta potential of lime-NS and lime-MK pastes titrated with the PCEsuperplasticizers


• 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


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


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

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Zeta potential of lime-NS and lime-MK pastes titrated with PNS and LS


• 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: 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%


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



SEM examination of mortars with PCE1

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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


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


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

role of different superplasticizers on hydrated lime...

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