potentials of polysaccharides to control the rheology of

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POTENTIALS OF POLYSACCHARIDES TO

CONTROL THE RHEOLOGY OF CONCRETE

Wolfram Schmidt

10.03.2021

Congratulations – 30 years of Conference

Series “Rheology of Building Materials”

10.03.2021Rheology of Building Materials | Online Colloquium | 30 Years | virtual Regensburg Potentials of polysaccharides to control the rheology of concrete | [email protected] | BAM

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Thank you for 30 years of

– Interesting talks

– Exciting discussions

– Hosting the “rheology family”

https://www.150.bam.de

Photo: Schleibinger Photo: Schleibinger

Photo: Schleibinger Photo: Schleibinger

Polysaccharides

Role of polysaccharides in rheology


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2011

2017

2015

Past presentations on polysaccharides on this conference by the presenter:

- Influences of modification (2011)

- Casting robustness (2015)

- Sustainability(2017)

Polysaccharides



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https://tu-dresden.de/bu/bauingenieurwesen/ifb/forschung/spp2005

Past presentations on polysaccharides on this conference by the presenter:

- Influences of modification (2011)

- Casting robustness (2015)

- Sustainability(2017)

- Future casting technologies will require new admixture groups that can tailor the rheology at every process step.

Polysaccharides



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Superplasticizers can disperse particles and thus reduce the yield stress.

This alone cannot sufficiently create the rheological specifications required for more industrialised processing.

Polysaccharides can become an important group of novel agents in concrete technology.

Polysaccharides

What are polysaccharides?


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– Polysaccharides are macromolecules consisting of monosaccharides (sugar)

– The most important ones occurring in nature are cellulose and starch, which consist of glucose only.

Starch

Cellulose

Polysaccharides



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– Often polysaccharides are branched.

Starch

Amylose (linear, small)

Amylopectin (branched, huge)

Polysaccharides



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– Often polysaccharides are branched.

– More complex polysaccharides used in construction are e.g. diutan gum and guar gum

Starch

Diutan gum

Glucose Glucuronate Glucose Rhamnose

Rhamnose Rhamnose

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Starch


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Starch

Effect in liquid phase


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Starch

Diutan gum

Starch

Peculiarity of starch


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No particles In presence of particles In presence of PCE

Starch

Yield stress and particle interactions


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– With increasing particle volume fraction, the effect of starch becomes stronger.

– At very low w/p it is stronger than diutan gum.

Starch

Influencing factors


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– Application (liquid/solid)

– Ratio of amylose and amylopectin

– Size and/or Mw of amylopectin

– Mode of modification

– Degree of substitution

– Presence of other polymers, e.g. PCE

– Adsorption

– Time / cement hydration

Starch



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0

20

40

60

80

100

120

140

160

180

0.00% 0.25% 0.50% 0.75% 1.00% 1.25% 1.50%

Dre

hm

omen

t [N

mm

]

Polymergehalt [M.-% des Pulvers]

Kartoffelstärke

Cassavastärke

-10

10

30

50

70

90

110

130

150

0 40 80 120 160 200 240

Dre

hm

omen

t [N

mm

]

Umdrehungsgeschwindigkeit [Upm]

Referenz

Kartoffel-

stärke

Cassava-

stärke

Cassava starch

Potato starch Potato

starch

Cassava

starch

Reference

Polymer content [% by weight of of powder] Rotational speed [rpm]

Torq

ue [

Nm

m]

Torq

ue [

Nm

m]

Starch



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Cassava starch

→ Negative zeta potential with Ca2+

→ Rhyd ~ 100 nm

Cassava Potato

Starch



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https://youtu.be/4H-0R75Zyv0?list=PLKqa3Uo_GQNs0mogyrcCYusuYtbJWOcT3

Starch



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https://youtu.be/4H-0R75Zyv0?list=PLKqa3Uo_GQNs0mogyrcCYusuYtbJWOcT3

Potentials:• inexhaustible global availability• great variability• low cost

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Acacia gum


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Acacia gum

Typical uses and properties


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– Easily water soluble gum

– Grows in the tropical and subtropical regions of Africa, India, and the Americas

– Typical use in food industry and cosmetics

– ¾ of the global consumption is produced in Sudan

Acacia gum

Effect in cementitious materials


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0

10

20

30

40

50

60

70

80

90

100

0.00% 0.05% 0.10% 0.15% 0.20%

Dre

hm

omen

t [N

mm

]

Polymergehalt [M.-% des Pulvers]

PCE (Fertigteil)

PCE (Transportbeton)

Akaziengummi (Sudan)

Akaziengummi (Südafrika)

Ligninsulfonat

PCE (pre-cast)

PCE (ready mixed)

Acacia gum (Sudan)

Acacia gum (South Africa)

Lignosulfonate

Polymer content [% by mass of powder]

Torq

ue [

Nm

m]

Stabilising effectPlasticizing effect

Acacia gum

Performance specifications


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w/c = 0.3

0.35% GA

w/c = 0.4

0.35% GA

Workability depends on:

– Dosage of gum

– Mixing intensity

– Mixing duration

– Particle volume fraction

– No plasticizing effect at very low w/c

– Plasticizing effect at moderate w/c

Acacia gum

Performance specifications


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Acacia gum

→ Negative zeta potential

→ With Ca2+ wide range of Rhyd ~ 10nm-2µmPotentials:• not yet commercialised in many regions in the world• occurs in regions with restricted access to admixtures• no complex processing required

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Triumfetta pendrata A. Rich


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What is it?


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Par Tatoute — Travail personnel, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=19808793

0.08% Nkui


Thixotropy


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Similar flowability

after 15 x lifting and

dropping

Significant flow

reduction only under

gravity load


Thixotropy


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20

40

60

80

100

120

140

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Time [min]

Sh

ear

stre

ss [

Pa]

Sh

ear

rate

[1/

s]


Thixotropy


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→ Negative zeta potential

→ With Ca2+ agglomerates up to 5 µmPotentials:• Rapid structural build-up without need to accelerate

the cement hydration

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Summary and outlook


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Summary and outlook

Biopolymers vs. synthetic polymers


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Polysaccharides have enormous potentials as rheology modifiers

• Starch

• Acacia gum

• Bark gum of Triumfetta

The approach is different from synthetic polymers, which can be tailored to the application:

1. first understanding of basic mode of operations

2. Identify ideal use


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Summary and outlook

New sources need to be identified

RefAnimal based

Bio-wastebased

Plant based


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Summary and outlook

Sustainability potentials

http://globe.rilem.net

GLOBE Global Consensus on Sustainabilityin the Built Environment

Circularity – environment - socio-economic equity

www.bam.de

Thank you for your attention.

Contact:

Wolfram Schmidt

FB 7.4

Email: [email protected]


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potentials of polysaccharides to control the rheology of

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