super plasticizers (mubashir)

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Superplasticizers

Guided by:

Er. Shaista Kanni.

Lecturer, Deptt. Of

Civil Engg.

SSM College ofEngg. & Tech.

Presented by:

Mubashir

Bashir.

Enrollment.

No: 1213.B.E 7th Sem,

Civil.


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CONTENTS

Super plasticizers

Introduction.

The evolution and development of

super plasticizers.

How plasticizers work in concrete.

Material and experimental methods.

Results and discussion.


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INTRODUCTIONAlmost magically like an alchemist turning lead into gold, super plasticizers

transform stiff low-slum concrete into flowing, pourable, easy placed concrete. Super plasticizers are polymers which added to concrete, increase the

fluidity at early stage without affecting the setting and hardening behaviour of

concrete.

They can improve workability, speed finishing, increase strength and help

reduce shrinkage and thermal cracking. Among the most important admixtures presently used in preparing concrete

are super plasticizers, which are preferred for their ability to enhance concrete

properties, making it :

More workable and easier to place.

Have better mechanical behaviour due to low water cement ratios required.

Cheaper because the cement content can be optimised.

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Main Purpose

Produce flowing

concrete. Easy placement .

High-strength .

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The evolution and development of super plasticizers.

Today admixtures constitute an essential part of concrete technology. The

most important ones are super plasticizers, which play the most effective role

in this activity.

The first research findings were published by the American Duff, A. Abrams

in 1918 under the title Design of Concrete Mixtures.

In concrete technological terms : the plasticizers appeared at the beginning of

the 20th century.

The application of increasingly effective materials led to the introduction of

new terms denoting stronger plasticizing effects. These new materials were

named Super plasticizers.

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Contd.

To date the latest development in super plasticizer technology is given infigure.

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How plasticizers work in concreteDeflocculation:

Portland cement particles have a strong tendency to flocculate when mixed with

water.

This tendency is the result of several types of interactions e.g;

i). Vander Walls interaction.

ii). Electrostatic interactions, and

iii). Strong interactions (or bridging).

To achieve a homogenous distribution of water and the optimal water cement

contact the cement particles must:

i). be properly deflocculated.

ii). be kept in a state of high dispersion.

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Super plasticizers

Contd.Other Aspects:

Reduction of surface tension.

Induced electrostatic repulsion between particles.

Lubricating film between cement particles.

Change in morphology of the hydration products, and

Induced steric hindrance preventing particle-to-particle contact.


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Important factors Type of plasticizer.

Dosage.

Time of addition of

super plasticizer.

Amount of cement.

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Benefits

Super plasticizers

Reduce machine

wear.

Better surfacetexture.

Improve strength in

less time.

Reduce

absorption.

Eliminate fine


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Disadvantages

Super plasticizers

High cost.

Brief action (picture:

restoration of the Queen

Isabella Causeway after collapse

in Sep. 15, 2001, time was very

important). Need strong, sealed forms.


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Materials and Experimental methods

Three types of super plasticizers were investigated for this study.

Their chemical structures are described in the table given below:

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Contd

The three super plasticizers were:

1. A polycarboxylate-type super plasticizer with a

polyoxyethylene graft chain (PCP).

2. A polynapthalene-sulphonate polymer (PNS).

3. A diphosphonate terminated mono-functionalpolyoxyethylene polymer.

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Results and discussionThe interaction of super plasticizers with C3A when

hydration occurs in presence of gypsum was studied

with three types of super plasticizers. Diphosphonate

does not modify the average rate of precipitation. No

adsorption occurs during the first minutes. PNS may

act on C3A hydration by decreasing its dissolution rate,

in consequence of its strong initial adsorption.

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Contd

PCP also slows down precipitation, but the decrease of

precipitation is less strong than PNS. Whereas PCP may

decrease the C3A dissolution rate. The comparison betweenthe amount of super plasticizer adsorbed during the

precipitation is given in the following bar chart:

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Super plasticizers

Comparison between the amount of super plasticizer adsorbed during the precipitation.


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References

http://www.chemisol.com

http://www.edpsciences.org

http://www.fhwa.dot.gov/infrastructure

http://www.fritzpak.com

http://www.precastconcretebc.com

http://www.reefball.org/adva

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Thank You!


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super plasticizers (mubashir)

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