Spiratos Presentation - Chemical Admixtures and Sustainability

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Chemical Admixtures :

Essential Components of Modern Concrete

Nelu SpiratosHandy Chemicals Ltd.

120 boul. de l'Industrie

Candiac, Qc, Canada

J5R 1J2

CANMET / ACI INTERNATIONAL CONFERENCE ON

ADVANCES IN CONCRETE TECHNOLOGY IN THE MIDDLE EAST

Dubai, November 19-20, 2008

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Scope of Presentation

• Trends in the use of concrete chemical admixtures

• Impact of admixtures towards concrete QUALITY

• Contributions of admixtures to concrete TECHNOLOGY

• Admixtures contributions to concrete SUSTAINABILITY

• Admixtures challenges ahead

• Conclusion

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Trends in Consumption of Chemical Admixtures

0

500

1000

1500

2000

2500

3000

1992 1996 2001 2006 2011

Y ear

Mil

lio

n U

S$

World

NorthAmeric a

As ia/P ac ific

Freedonia

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Admixture Consumption by Type (World)

Freedonia

0

500

1000

1500

2000

2500

3000

1992 1996 2001 2006 2011

Year

Mil

lio

n U

S$

ChemicalAdditiveDemand

WaterReducers

SetControllers

Colorants,AirEntrainers &Other

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Evolution of Chemical Admixtures

Development of admixtures according to :

• Demands on concrete material properties

• Changes in binder composition

• Evolution in construction technologies

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Demands on Concrete Material Properties

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Demands on Concrete Properties

• Higher moduli (compressive, tensile, flexural)

• Greater freeze-thaw resistance

• Improved durability

• Minimum shrinkage cracking

• Minimum rebar corrosion

• No Alkali-Aggregate reaction

• Etc, …

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Increasing compressive strength

Achieved through:

• Low W/C

• Effective WR

• Superplasticizers

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Enhanced strength and durability

Achieved through:

• Low porosity

• Fine pore structure

Using:

• Low w/c

• SCM‟s (SF, FA)

• Superplasticizers

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Greater improving freeze-thaw resistance

Achieved through:

• Network of fine air voids

Using:

• Air-entraining agents

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Minimizing shrinkage-cracking

Reduce drying

shrinkage cracking

through SRA‟s

(shrinkage reducing

admixtures)

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Preventing rebar corrosion

By reducing ingress of chemical species

Achieved through:

• Low porosity

• Fine pore structure

• And new admixtures :

corrosion inhibitors

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Minimize alkali-aggregate reactions

10 microns

Expansive reaction at aggregate-matrix interface

Swelling and microcracking

Mitigate with Lithium-based admixtures

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Changes in Binder Composition

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Due to incorporation of :

• Different forms of Ca-sulfate

• Fillers (e.g., limestone)

• Supplementing cementitious materials (e.g.,

natural pozzolans, SF, FA, BFS, calcined clays)

• Others

Changes in Binder Composition

….. Affecting performance of all admixtures,

…. sometimes requiring new admixtures

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Changes in Binder Composition:

Upon incorporation of Fly Ash

Carbon particles in FA

FA-carbon interferes with air-entraining admixtures

Typical FA particles

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AEA conc.

%A

ir e

ntr

ain

ed

Influence of FA-carbon compensated by new „Sacrificial‟ Admixtures

FA/Cement + 0.05% Sacrificial Agent

Cement

Cement + Fly Ash

Changes in Binder Composition:

Air entrainment in the presence of FA-Carbon

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Evolution in Construction Technologies

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Pumpable concrete through Superplasticizers

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Non-segregating flowing concrete

Achieved with :

Viscosity-Enhancing

Admixtures (VEA)

Cohesive, self-consolidating concrete

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Chemical Admixtures enable

• Pumpable concrete

• Self-levelling concrete

• Self-consolidating concrete

Leading to

• Increased throughput

• Reduced labour requirements

• Reduced construction time


Admixtures impact on construction technologies

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Chemical Admixtures and Sustainability

of Concrete Technologies

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First-Order Contributions

Sustainability related to material properties

Concrete with higher strength Use less concrete

Concrete with greater durability Longer service life

Strength with less cement Use less cement

Strength with less water Use less water

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Second-Order Sustainability Contributions

Related to SCM's

Incorporation of FA, BFS, SF, etc. improve

STRENGTH and DURABILITY (FIRST–ORDER gains)

+

• Beneficiation of industrial residues

• Reduction of cement consumption

• Less CO2 from cement fabrication (environment)

• Energy savings (clinker, grinding)

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Third-Order Sustainability ContributionsRelated to concrete technologies

• Fluid concrete Reduced batching energy

• Pumpable concrete Reduced transportation energy

• Self-consolidation Lower placing energy (vibration)

• High workability Reduced construction times

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Fourth Order Sustainability ContributionsRelated to manufacturing of admixture

Polynaphthalene sulfonates

(PNS)

CH2

SO3Na

nH2SO4

Secondary industrial

materials

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The Admixture Challenge Ahead

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Resolve fundamental issues

• Understand the chemistry and mode action

of each admixture

• Design molecular structure of admixtures for

specific function (e.g. Polyacrylate esters)

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Predicting incompatibilities

• Cope with the variable chemistry of binders

• Avoid deleterious interactions with

components of the cement

(same with aggregate)

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Ensuring performance under all conditions

• Avoid interference between admixtures

• Enhance “robustness” of admixtures with respect to

application conditions

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Conclusions

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A First Conclusion

… the development of concrete materials

and technologies was largely supported and

driven by the timely introduction of multiple

new chemical admixtures

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A Second Conclusion

Concrete chemical admixtures:

are essential components of quality concrete

contribute directly to beneficiation of secondary

industrial materials or chemicals

are unavoidable components

of modern sustainable concrete technologies !

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Spiratos Presentation - Chemical Admixtures and Sustainability