Cement Admixtures
Transcript of Cement Admixtures
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CEMENT ADMIXTURES Focussing on the interface
MCyTM
Pablo García Triñanes [email protected]
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Cement particle
Superplasticizer
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1. PROPERTIES / TYPES 2. APPLICATIONS 3. FURTHER READING
SLUMP TEST
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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. [email protected]