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BY:- LAUKUSH KUMAR 

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INTRODUCTION

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HISTORY

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WHY ARE THEY USED

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WHY ARE THEY USED 

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HOW APPLIED

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CLASSIFICATION OF ADMIXTURES

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CHEMICAL ADMIXTURES 1.accelerators

2.retarders

3.water reducing admixtures 4.grouting admixtures

5.air-entraining admixtures

6.permeability reducing admixtures

7.plasticizers

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MINERAL ADMIXTURES 1.fly ash

2.blast furnace slag

3.rice husk ash 4.silica fumes

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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 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:

Using:

• Low w/c 

• SCM‟s (SF)

• 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 Achieved through:

• Low porosity 

• Fine pore structure  • And new admixtures :

corrosion inhibitors

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Minimize alkali-aggregate reactions

Mitigate with Lithium-based admixtures

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Changes in Binder Composition Due to incorporation of :

• Different forms of Ca-sulfate

• Fillers (e.g., limestone)  • Supplementing cementitious materials (e.g.,

natural pozzolans, SF)

Others

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Changes in Binder Composition: Upon incorporation of 

Fly Ash.

FA-carbon interferes with air-entrainingadmixtures.

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Evolution in Construction

Technologies Pumpable concrete

throughSuperplasticizers.

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Evolution in Construction

Technologies Cohesive, self-

consolidating concrete.

 Achieved with :

 Viscosity-Enhancing

 Admixtures (VEA).

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Evolution in Construction

Technologies Admixtures impact on construction technologies:-

Chemical Admixtures enable

• Pumpable concrete• Self -levelling concrete

• Self -consolidating concrete

Leading to

• Reduced labour requirements

• Reduced construction time 

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The Admixture Challenge Ahead Resolve fundamental issues:-

• Understand the chemistry and mode action

of each admixture. • Design molecular structure of admixtures for

specific function .

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Conclusions A First Conclusion:-

… the development of concrete materials

and technologies was largely supported anddriven by the timely introduction of multiple

new chemical admixtures

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Conclusions A Second Conclusion:-

Concrete chemical admixtures:

are essential components of quality concrete contribute directly to beneficiation of secondary 

industrial materials or chemicals.