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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.
Super plasticizers
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Main Purpose
Produce flowing
concrete. Easy placement .
High-strength .
Super plasticizers
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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.
Super plasticizers
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Contd.
To date the latest development in super plasticizer technology is given infigure.
Super plasticizers
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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.
Super plasticizers
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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.
Super plasticizers
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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:
Super plasticizers
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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.
Super plasticizers
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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.
Super plasticizers
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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:
Super plasticizers
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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
Super plasticizers
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Thank You!
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