Ara A. Jeknavorian, Ph.D. Eric Koehler, Ph.D. W.R. Grace – … · · 2011-03-29Lack of good...

2010 Concrete Sustainability Conference 1 © National Ready Mixed Concrete Association

Ara A. Jeknavorian, Ph.D.Eric Koehler, Ph.D.W.R. Grace – Conn.Cambridge, MA

Use of Chemical Admixtures to Modify the Rheological Behavior of Cementitious Systems Containing Manufactured Aggregates


OUTLINEIssues associated with the use of manufacturedIssues associated with the use of manufactured (“harsh”) sands for concrete

Searching for correlations between sand properties and mortar rheology – w/ and w/o increased cement paste or VMA.

Effect on Fines on Concrete WorkabilityEffect on Fines on Concrete Workability

Polycarboxylate-Superplasticizers and Clay

Summaryy

2010 NRMCA Concrete Sustainability Conference 2


Properties associated with the use of manufactured (“harsh”) sands for concrete

Dependency on manufactured sands is increasing worldwide.

Fine aggregate from manufactured sands: (a) generally more angular; gg g ( ) g y g ;(b) rougher surface texture than naturally weathered sand particles; and (c) significant quantity rock dust.

Irregular shapes contributes to increased loose density which inIrregular shapes contributes to increased loose density, which in turn, requires the concrete mixture to have higher void-filling paste content.

The fine fraction ( -75 um): (a) possibly rich in mica and clay minerals; (b) both increased/decreased water demand for a required slump, and (c) polycarboxylate adsorption.



Aggregate Characteristics: Shape, Angularity, and Texture

ShapeCoarsest Scale

Numerous parameters describing particle geometry are used in many different industries.

Relative length width thickness Sharpness of the corners Roughness of particle surface

AngularityIntermediate Scale

TextureFinest Scale

Relative length, width, thickness Sharpness of the corners Roughness of particle surface

length

width

thickness

WorkabilityStrength

length

The smaller the particle, the greater the effect on workability.



Comparison of Sand Shape andComparison of Sand Shape and Surface Texture for Arizona Natural and Manufactured sandssands

Natural Sand

- round particles - smooth surface texturesmooth surface texture

Manufactured SandManufactured Sand

- elongated particles - rough surface texture



Aggregate characteristics affecting concrete rheology

Shape Gradation Cleanliness

Sharp corners increase Small particles are not Mica clays and otherSharp corners increase friction between

particles

Small particles are not available to fill voids

between larger particles

Mica, clays and other deleterious materials

increase water demand; smectite particularly

increase polycarboxylate basedWell graded Poorly graded

Shape: relative principle dimensionsAngularity: sharpness of corners polycarboxylate-based

admixture demand

g y gAngularity: sharpness of corners (most important)Texture: surface roughness (least important)

Less paste More paste



Effect of Manufactured Sands on Concrete Performance

Reduced workability due to angularity and increased surface area.

Increased segregation due to gap gradation.

Increased pumping pressure.

Increased effort for placing and finishing operations.



Common Practices to Mitigate Effects of Manufactured Sand

Increase paste content

Add/increase SCM

Mid-range and PC-based high range water reducers

Blend with natural sands

Viscosity-modifying Admixture (VMA)Viscosity-modifying Admixture (VMA)



Pump Pressure as a Function of

Effect of Manufactured Sands and VMA on Pump Pressure

Mix Design kg/m3% Manufactured Sand

16

18

20

Mix Design, kg/m3

Cement 248

Fly Ash 65

10

12

14

16

ress

ure,

MPa

VMA, 3 ml/100kgWater 178 – 186 kg/m3

WRA 260 ml/100 kg

2

4

6

8

Pum

p Pr

0.92 1.0 1.02 Slump 115-127 mm


0

2

0 20 40 60 80 100

% Manufactured Sand

Sand/Stone


L k f d l i h d f h

Challenges to Predict Effect of Manufactured Sands on Concrete Performance

Lack of good evaluation methods for shape angularity and texture of sands (and fines in sand).

L k f l ti b t d h i lLack of correlation between sand physical characteristics and fresh concrete performance.

Mi t ti i th d (i ACI 211) d tMixture proportioning methods (i.e. ACI 211) do not incorporate effect of aggregate shape and texture.

ASTM C33 t il it bl f h h dASTM C33 not necessarily suitable for harsh sands - max 7% fines –75 μm. [Fines content should be higher].



Manufactured Sand Test Protocol Sieve Size, mm

Cum % retained by mass

5 2Physical characteristics of Natural and Manufactured:

– Grading by Sieve Analysis, FM

5 22.5 15 1.25 35 0.630 55 0.315 79

– Particle Shape/Texture (ASTM C 295, Image Analysis)– Fines content and nature– Uncompacted Void Content (ASTM C1252)

0.315 790.160 97 Total 283 F.M. = 283/100 = 2.83

p ( )

Rheological properties:–Mortar protocol w/ and w/o VMAYield and viscosity measurements–Yield and viscosity measurements



C C i lContec Coaxial Cylinder Rheometer



Rheological Properties: Yield Stress and Viscosity

Bi h M d l

τ =τ = ττ ++ μμγγτ =τ = ττ ++ μμγγτ =τ = ττ ++ μμγγτττ

Bingham Model

τ = τ = ττ00+ + μμγγ

μμτ = τ = ττ00+ + μμγγτ = τ = ττ00+ + μμγγ

μμμμress

ress

ress G’, viscosity

τ0μ

: yield value (Pa): yield value (Pa)

: plastic viscosity (Pa: plastic viscosity (Pa••s)s)

1ττ00

μμτ0μ



1ττ00

μμτ0μ


: plastic viscosity (Pa: plastic viscosity (Pa••s)s)τ0μ



1ττ00

μμSh

ear s

tSh

ear s

tSh

ear s

t

H’μ : plastic viscosity (Pa: plastic viscosity (Pa••s)s)μ : plastic viscosity (Pa: plastic viscosity (Pa••s)s)μ : plastic viscosity (Pa: plastic viscosity (Pa••s)s)μ : plastic viscosity (Pa: plastic viscosity (Pa••s)s)

γRate of shear γRate of shear γγRate of shearH’=yield stress



Natural and Manufactured Sands used in this Study

Location and Type of Sands

Manufactured Sands(MS) Natural Sand (NS) Location EN Standard Sand - Europe EN Standard Sand - Europe

GC-HS HC-NS Central California HSLO-HS HSLO-NS Central California MARI-HS NS Arizona

CP-HS CP-NS ArizonaBARGE-HS HV-NS Southern California

S-HS DUR-HS Southern California D-HS -- Illinois FL-HS FL-NS Florida



Hanson Durbin NS100

S. California Natural Sand

5060

7080

90100

ativ

e Pa

ssin

g

PhysicalFM: 2.8% Passing #100: 5.2

010

2030

40

#4#8#16#30#50#100#200

% C

umul

a%UCV: 38.7G’: 132.5 Pa.sH’: 44.5 Pa

#4#8#16#30#50#100#200

Seive SizeMineralogy: Crushed granitic rock containing biotite (crystalline cleavage surfaces evident).

Shape: 1 EquantTexture: 4 Sub AngularCleanliness: 2 Clean


STC Factor: 73 mm


Hanson Mexican HS

8090

100

ng

S. California Manufactured Sand

304050607080

umul

ativ

e Pa

ssin

PhysicalFM: 3.20% Passing #100: 3.5

01020

#4#8#16#30#50#100#200

Seive Size

% C

u

%UCV: 42.57G’: 354.3 PaH’: 57.5 Pa.s

Mineralogy: : Quartz with high of mica platy flakes Shape: “2” Equant with some p qflaky micaTexture: “4” Coarser size containssome rounded but more angularparticles. Fines were more sub


particles. Fines were more subangular texturedCleanliness: 3 DustySTC Factor: 9


Mortar Compositions with VMA and Increased Paste Contents

Control

Control w/VMA

Control + 10% Paste

Control + 20% Paste

Control + 30%

Control + 40%

Paste PasteCement 400 400 440 480 520 560 Sand 800 800 800 800 800 800 Water 188 188 207 225 244 263 % VMA, % s/s

- 0.0035 - - - -

w/c = 0 47; EN 196 sand


w/c = 0.47; EN 196 sand


Correlation of Mortar Flow with Yield Stress

Without VMA

140

150

MNSMGCRBHMCGCFL

120

130

140

m

FLD

100

110

Mor

tar F

low

, m

70

80

90


600 50 100 150 200 250 300 350 400 450

Yield Stress, PA


Yield measurement of mortar mixtures prepared with natural and manufactured sands

400450 M

250300350400

' (Pa

)

EN B B

B

M M

M

M

NN

ress

100150200250

Yiel

d G

'

N N N N NM M196

B B

Yiel

d St

r

050

100

EN

e N

S

n N

S

O N

S

a N

S

e H

S

x H

S

n N

S

8020

6040

e H

S

4060

2575

a N

S

a H

S

x N

S

O H

S

n H

S

Riv

erH

S

Y


Flor

ida

Lim

esto

ne

Han

son

Dur

bin

Han

son

SLO

Han

son

Cal

iforn

ia

Dol

omite

Cen

tral

Pho

enix

Han

son

Vulc

an CP

CP

Flor

ida

Lim

esto

n e CP

CP

Mar

icop

a

Gra

nite

Can

ada

Cen

tral

Pho

enix

Han

son

SLO

Han

son

Mex

ican

(Bar

ge)

Mar

icop

a R

Bot

tom

H


Laboratory Mortar Rheology ResultsMixes with No Admixture450

ENMaricopa NSMaricopa River Botton HSHanson Mexican HS (Barge)

Contec Mortar Rheology Measurements

M MS

350

400

( g )Granite Canada HSFlorida limestone HSDolomite HSHanson Vulcan NSHanson California NSFlorida Limestone NSHanson SLO HS

M-MS

H-MS

250

300

G' (

Pa)

Hanson SLO HSHanson SLO NSCentral Phoenix HSCentral Phoenix NSCP2575CP4060CP6040CP8020

M-NS FL-MS

CP-NS

Stre

ss

150

200

Yiel

d G CP8020

Durbin NS

H NSCP-MS

Yiel

d

50

100H-NS

FL-NSNo significant trend in yield and viscosity for NS vs MS mortars.

However, NS vs HS sands from same source exhibit clear


010 20 30 40 50 60 70 80

Viscosity H' (Pa.s)

difference in mortar rheology.


Correlation Mortar Yield vs FM

400

450ENFlorida Limestone HSDolomite HSGranite Canada HSMaricopa River Bottom HSHanson Mexican HS (Barge)Maricopa NSHanson Vulcan NS

300

350

a)

a so u ca SHanson California NSFlorida Limestone NSCentral Phoenix HSCentral Phoenix NSCP2575CP4060CP6040CP8020es

s

200

250

Yiel

d G

' (Pa Hanson Durbin NS

Hanson SLO HSHanson SLO NS

Yiel

d St

re

100

150

Y


100

2 2.5 3 3.5 4 4.5

Fineness Modulus


Correlation Mortar Yield vs % Uncompacted Voids450

EN

350

400

ENFlorida Limestone HSDolomite HSGranite Canada HSMaricopa River Bottom HSHanson Mexican HS (Barge)Maricopa NSHanson Vulcan NSHanson California NSFlorida Limestone NS

300

350

(Pa)

Central Phoenix HSCentral Phoenix NSCP2575CP4060CP6040CP8020Hanson Durbin NSHanson SLO HSHanson SLO NS S

tres

s

200

250

Yiel

d G

'

Yiel

d

100

150


5035 37 39 41 43 45 47

% Uncompacted Voids


Correlation Mortar Yield vs Shape

450 EN

350

400

450 ENFlorida Limestone HSDolomite HSGranite Canada HSMaricopa River Bottom HSH M i HS (B )

250

300

d G

'(Pa)

Hanson Mexican HS (Barge)Maricopa NSHanson SLO HSHanson SLO NSHanson Durbin NS S

tres

s

100

150

200

Yiel

d Hanson Vulcan NSHanson California NSCentral Phoenix HSCentral Phoenix NSFlorida Limestone NS

Yiel

d

0

50

0 1 2 3 4 5


0 1 2 3 4 5

Shape (1 Equant; 2 Predom Equant, 3 Equal Distr Shapes, 4 Predom

Elong, 5 Elongated and Flaky)


Correlation Mortar Yield vs Texture

450

350

400ENFlorida Limestone HSDolomite HS

250

300

G' (

Pa)

Dolomite HSGranite Canada HSMaricopa River Bottom HSHanson Mexican HS (Barge)Maricopa NSHanson SLO HSSt

ress

150

200

Yiel

d

Hanson SLO HSHanson SLO NSHanson Durbin NSHanson Vulcan NSHanson California NSCentral Phoenix HS

Yiel

d

0

50

100 Central Phoenix NSFlorida Limestone NS


01 2 3 4 5 6Texture

(1 Well Rounded, 2 Rounded, 3 Sub Rounded, 4 Sub Angular, 5 Angular)


Correlation Mortar Yield vs Cleanliness450

350

400 ENFlorida Limestone HSDolomite HSGranite Canada HS

250

300

G' (

Pa)

Maricopa River Bottom HSHanson Mexican HS (Barge)Maricopa NSHanson SLO HSHanson SLO NSSt

ress

150

200

Yiel

d Hanson SLO NSHanson Durbin NSHanson Vulcan NSHanson California NSCentral Phoenix HS

Yiel

d S

50

100Central Phoenix NSFlorida Limestone NS


00 1 2 3 4 5

Cleanliness (1Very Clean, 5Extremely dirty)


Correlation Mortar Yield vs. STC Factor

450

350

400 ENFlorida Limestone HSDolomite HSGranite Canada HS

250

300

G' (

Pa)

Granite Canada HSMaricopa River Bottom HSHanson Mexican HS (Barge)Maricopa NSHanson SLO HSSt

ress

150

200

Yiel

d G

Hanson SLO NSHanson Durbin NSCentral Phoenix HSCentral Phoenix NSHanson California NS

Yiel

d S

50

100Hanson California NSFlorida Limestone NS


03 4 5 6 7 8 9 10 11 12 13

STC Factor (Shape+Texture+Cleanliness)


Mortar Rheology with VMA vs Increase paste content

VMA

F l t d i i l h id i ti d l ti- Formulated anionic polysaccharide imparting pseudoplasticbehavior.

- Viscosity decreases/increases instantaneously by applying/removing shear forceapplying/removing shear force

- Water retention capability as a function of dosage



Change in Mortar Yield as a Function of VMA and Cement Paste Addition

VMAR3450

300

350

400

Yiel

d

MNS

MGCRBCement ResponsAdmixture Response

0.003% s/s VMA

ess

Man. sand

200

250

300

ppar

ent Y

pe

No VMAw/ VMA

Yiel

d S

tr

100

150

A

Natural sandEquivalent Paste


500 20 40

% Additional Cement


Reduction in Yield stress as a Function of Added Cement Paste



% Equivalent Paste with 0.003% VMA s/s at Constant Yield Stress

15.51618

Mortars with Manufactured Sand

10 9.7 9.7 98

810121416

t Pas

te

6

3.3 2.8 2.6

002468

S% E

quiv

alen

t

0

Flor

ida

Lim

esto

ne H

S

CP

4060

Dol

omite

HS

Mar

icop

a R

iver

Bot

tom

HS

CP

8020

CP

100

CP

6040

Gra

nite

Can

ada

HS

Han

son

Mex

ican

HS

(Bar

ge)

Han

son

SLO

HS CP

2575

%


Less Harsh Sand More Harsh Sand


Correlation of VMA and Cement Paste Additions on Yield Stress of Mortar with Harsh Sands

20

Roughly inverse relationship between effects of cement paste and VMA on Yield Stress indicates different mechanisms on mortar rheology.

14161820

Change in Yield Stress

/ VMA

68

1012w/ VMA

0246

0 2 4 6 8


0 2 4 6 8Change in Yield Stress/% added paste


Mechanism of yield stress reduction as a functionof VMA and cement paste additions

Addition ofAddition of

V-MAR3 lubricates grain surfaceV-MAR3 lubricates grain surface

Not enough energy for polymer alignmentNot enough energy for polymer alignment

Polymer alignment creates sliding surfacePolymer alignment creates sliding surface

Addition of V-MAR3Addition of V-MAR3

Under low energy Under low energy Under high energy Under high energy

Harsh sand Mortar mix

(Gravity, finishing)(Gravity, finishing) (Pumping, Vibration, lab Rheology)

(Pumping, Vibration, lab Rheology)

Addition of Cement pasteAddition of Cement paste

Paste volume separates grainsPaste volume separates grains

Grain separation allows adequate flowGrain separation allows adequate flow

Enough separation creates sliding surfaceEnough separation creates sliding surface



Microfines Can Be Good For Concrete

Microfines (<~100 microns) are often Laser PSD of Microfines and CementMicrofines (< 100 microns) are often removed from sand by washing or air classification. If these materials are clean and well-shaped, they can be beneficial for concrete

Laser PSD of Microfines and Cement

• Size: typically similar in size as cement, can enhance overall powder particle size distribution

• Shape: can vary widely and significantly impacts performance

• Cleanliness: should be largely free of clays, as indicated by a low methylene blue value

SEM Image of Microfines

Microfines can be similar in size, shape, and cleanliness as limestone filler, which is well-established for use in concrete.

2010 NRMCA Concrete Sustainability Conference 33Reference: Stewart, J., Norvell, J., Juenger, M., and Fowler, D.W. (2006). “Characterizing Minus No. 200 Fine Aggregate for Performance in Concrete” ICAR Report 107-1, International Center for Aggregates Research, Austin, TX.


Microfines in Conventional Concrete (Quiroga 2006)

Quahog et al. showed that replacement of natural sand with various

manufactured sands of various microfines contents reduced

workability due to shape gradingworkability—due to shape, grading (including <#200) and cleanliness of

manufactured sand. Additional decrease in workability was evident only at high

rates of microfines.

Increased methylene blue value clearly decreased flow. (Variations in other aggregate characteristics were partially

responsible for scatter.)Manufactured sands resulted in greater compressive strength,

even with higher microfines contents (constant w/c)

2010 NRMCA Concrete Sustainability Conference 34Reference: Quiroga, P.N., Ahn, N., Fowler, D.W. (2006). “Concrete Mixtures with High Microfines,” ACI Materials Journal, 103(4), 258-264.


Microfines in Conventional Concrete (Stewart 2006)Stewart showed that addition of pure clay (kaolinite, illite, montmorillonite) resulted in significant increases in water and HRWR (PC-based) demand for constant mortar flow, especially for montmorillonite.

In contrast, the addition of similarly sized fillers at 1% and 4% resulted in minimal change in water demand and slight decreases in HRWR demand.•GS: ground silica, 90% finer than 5 um•CCF: calcium carbonate 60% finer than 2 um

2010 NRMCA Concrete Sustainability Conference 35Reference: Stewart, J., Norvell, J., Juenger, M.G., Fowler, D.W. (2006). “Characterizing Minus No. 200 Fine Aggregate for Performance in Concrete,” (ICAR Report 107). International Center for Aggregates Research, Austin, TX.

CCF: calcium carbonate, 60% finer than 2 um•CCUF: calcium carbonate, 90% finer than 2um


Microfines in Self-Consolidating Concrete (Koehler 2008)

In evaluation of high microfines sands in Self-Consolidating Mortar (constant w/c and cementIn evaluation of high microfines sands in Self Consolidating Mortar (constant w/c and cement, reduced w/p), Koehler (2008) showed potentially beneficial effects depending on microfines

characteristics.Increased microfines content in the sand resulted in increased HRWR demand. For clean, well-shaped

microfines, HRWR demand was equal or less at 5%.

Increased microfines content resulted in lower viscosity (mini-v-funnel time) when the HRWR was adjusted for constant flow. The exception, GR-01, contained high mica content.

constant mini-slump flow constant mini-slump flow

2010 NRMCA Concrete Sustainability Conference 36Reference: Koehler, E.P. Fowler, D.W. (2008). “Dust of Fracture Aggregate Microfines in SCC” ACI Materials Journal, 165-173.


Aggregate Characteristics: Cleanliness

Clays micas and otherClays, micas, and other deleterious materials reduce rheology

Correct clay definition is Effect of Sodium Montmorillonite on

Concrete Water Demand for 3 in.

R2 = 1.00

20

25

30

nge

(%)

ycritical to understanding effects on concrete performance

Cl i l l i

Slump

10

15

ater

Con

tent

Cha• Clay minerals vs. clay size

minerals (<2 μm)

• Swelling vs. non-swelling clay minerals

0

5

0.0 0.2 0.4 0.6 0.8

Doped Sodium Montmorillonite Clay Content (% sand)

Wa

Swelling clays may:

• Increase water demand for given slump

Grace Data


• Increase required dose of polycarboxylate-based HRWR


New UV-Methylene Blue Test

Methylene blue is a function of clay content and clay activityMethylene blue is a function of clay content and clay activityA novel test method was developed to expedite and improve MBV results

• Existing titration method (e.g. AASHTO TP 57): titration test to determine amount of methyleneblue solution absorbed by clay

• New Grace UV-MBV method: UV-vis measurement of methylene blue solution to determineNew Grace UV MBV method: UV vis measurement of methylene blue solution to determine methylene blue dye depletion for solution in presence of clay bearing aggregates

One mixing of methylene blue solution rather than gradual titration enables faster results

Test is performed on entire sand sample, ensuring representative results

Results reported as mg of methylene blue per g of sand (not per g of microfines)

New UV Method

Methylene blue solution after mixing with clay-bearing sand, ready for UV measurement.

Titration Method

Gradual titration end point determined upon appearance of blue halo.

Methylene blue is a function of clay content and clay activity.


Source: Yool, A.I.G., Lees, T.P., and Fried, A. (1998). “Improvements to the Methylene Blue Dye Test for

Harmful Clay in Aggregates for Concrete and Mortar” Cement and Concrete Research, 28(10), 1417-1428.


Dose-Slump Response for PCP vs NSFC in Lab Concrete Customer RLT Sand and Lab $170 cement

150170

Slump, mm

90 110130 NSFC

PC

50 70

0 0.1 0.2 0.3 0.4


Polymer Dosage,


Relative change in Mortar Flow as a Function of Increasing Clay Content in Lab Sand

Na-Montmorillonite

220

240

200

220

(mm

)NSFC, 0.37%

160

180Flow

(

PCP, 0.13%

1400 0.5 1 1.5

Clay in Sand(%)



Proposed model of PCP - Clay InteractionC HC H 2C H 2 C HC H 2 C HC H 2 C HC HC H 2

N

N H 3

OC

C HC H 2C H 2 C H

CO

C H 2 C H

C O

N H

C H 2 C H

C O

OO H

OC

C HC H 2a b c d

IntercalationEdge Adsorption

C H 2

C HH 3 C

O

N H 3

C H 2

C HH 3 C

O

H 3 C C H

C H 2

C H 2

C H 2

O

C H 2

C H 2

C H 2

C H 2

O

xx

H 3 C

O

C H

C H 2H 3 C

O

C HC H

O

H 3 C

x

Clay Mineral


C H 2

O C H 3C H 2

O C H 3

O C H 3

C H 2

yy

y


In Summary……

Rheology measurements are useful tool to differentiate effect of manufactured vs natural sands on mortar workability.

A simple correlation between several key sand properties yand their effect on mortar rheology is not evident.

VMAs can offset decreases in workability when natural sands are replaced by manufactured sands in cementitiousp ymixtures.

Sands that respond weakly to increased paste content appear to be more strongly affected by VMA.appear to be more strongly affected by VMA.

Is it possible someday that manufactured sand will be used as readily as natural sand??



Getting SCC Right: Impossible??When you are from Boston, nothing is impossible!

1918 2004 2007If the Red Sox can make it happen, then making manufactured sand as easy to use as the natural

1918, 2004, 2007


ystuff is surely possible, and it won’t take 86 years!


THANK YOUTHANK YOUY r Q ti n ar W l mYour Questions are Welcome…..


Ara A. Jeknavorian, Ph.D. Eric Koehler, Ph.D. W.R. Grace – … · · 2011-03-29Lack of good...

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Transcript of Ara A. Jeknavorian, Ph.D. Eric Koehler, Ph.D. W.R. Grace – … · · 2011-03-29Lack of good...