Cement Admixtures

CEMENT ADMIXTURES Focussing on the interface

MCyTM

Pablo García Triñanes pablo.garcia.trinanes@usc.es

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Cement particle

Superplasticizer

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1. PROPERTIES / TYPES 2. APPLICATIONS 3. FURTHER READING

SLUMP TEST

1. PROPERTIES / TYPES 2. APPLICATIONS 3. FURTHER READING

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WATER-REDUCING

ADMIXTURES

AIR-ENTRAINING ADMIXTURES

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1. PROPERTIES / TYPES 2. APPLICATIONS 3. FURTHER READING

1.- Salts and modifications of hydroxylized carboxylic acids (HC type); 2.- Salts and modifications of lignosulfonic acids (lignins); 3.- Polymeric materials (PS type).

CLASSIFICATION OF WATER-REDUCING ADMIXTURES

EXAMPLES OF SUPERPLASTICIZERS

1.- Sulfonated melamine-formaldehyde condensates (SMF); 2.-Sulfonated naphthalene-formaldehyde condensates (SNF); 3.-Modified lignosulfonates (MLS); 4.-Polyacrylates.

Cement hydration Sulfonic acid/water

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1. PROPERTIES / TYPES 2. APPLICATIONS 3. FURTHER READING

Improved workability

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1. PROPERTIES / TYPES 2. APPLICATIONS 3. FUTHER READING

Aggomerated cement particles in the presence of water

Addition of superplasticizer agent

Powerful linking, fluidization of the mixture by steric repulsion

Formation of crystals by reaction with water cancelling out the superplasticizers separating effect

TARJET: PRODUCE CONCRETE WITH GREATER FLUIDITY

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CLASSIFICATION OF AIR-ENTRAINING ADMIXTURES

1. PROPERTIES / TYPES 2. APPLICATIONS 3. FUTHER READING

1.- Salts of wood resins 2.- Synthetic detergents 3.- Salts of petroleum acids 4.- Fatty and resinous acids and their salts

MECHANISM

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1. PROPERTIES / TYPES 2. APPLICATIONS 3. FUTHER READING

BUBBLE SIZE 0,05-1,25 mm

DOSAGE 0,15 - 0,30 %

Overdosing can cause several reduction of compressive strength

SURFACE ACTIVE AGENTS

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1. PROPERTIES / TYPES 2. APPLICATIONS 3. FUTHER READING

Cement paste

ICE FORMATION IN AIR VOIDS

Ice α dS = psurf dV Sphere: psurf = 2α r Cylinder: psurf = α r

As the size of the sphere or the cylinder decreases, the magnitude of

the surface pressure increases.

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1. PROPERTIES / TYPES 2. APPLICATIONS 3. FURTHER READING

Resist freezing and thawing action. Increase permeability. Improve workability.

Increase workability (consistency). Higher compressive strength. Cement saving.

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1. PROPERTIES / TYPES 2. APPLICATIONS 3. FURTHER READING

REFERENCES

-Admixtures for concrete: Improvement of properties. Proceedings of the International RILEM Symposium. Taylor & Francis. (2006) ISBN 0-203-00875-8 -Concrete (2nd Edition) S. Mindess, J.F. Young, D. Darwin. Pearson Education. (2003) ISBN 0-13-064632-6 -Introduction to Modern Colloid Science. R.J. Hunter. Oxford Science Publications. (1994) ISBN 0-19-855386-2 -Concrete: Microstructure, Properties and Materials. P.Kumar Mehta, Paulo J.M. Monteiro. McGraw Hill (2006) ISBN: 0-13-175621-4 -Educational Guide to Admixtures, Additives and Water. CEMEX Mortars. Available on the web. -Superplasticizer effects on setting and structuration mechanisms of ultrahigh-performance concrete. V. Morin et al. Cement and Concrete Research. Vol. 31 63-71 (2001) -Superplasticizers: the wonder of fluid concrete. LAFARGE RESEARCH CENTER. Video available on the web.

pablo. garcia.trinanes@usc.es