admixtures for concrete - college of · pdf fileair-entraining admixtures water-reducing...

Admixtures for Concrete


Admixtures Air-entraining admixtures Water-reducing admixtures Plasticizers Accelerating admixtures Retarding admixtures Hydration-control admixtures Corrosion inhibitors Shrinkage reducers ASR inhibitors Coloring admixtures Miscellaneous admixtures


Air-Entraining Admixtures

Improve durability in concrete exposed to Freeze-thaw Deicers Sulfates Alkali-reactive environments

Improve workability

ASTM C 260 or AASHTO M 154ASTM C 260 or AASHTO M 154


Frost Damage


Scaled Concrete Surface


Water-Reducing Admixtures

Reduce mixing water required to produce a certain slump

Reduce water-cement ratio Reduce cement content Increase slump

Primarily used to:Primarily used to:


Water Reducing Admixtures

Type A ― reduces water content at least 5% tends to retard ― accelerator

often added Type D ―

reduces water content 5% min. retards set

Type E ― reduces water content 5% min. accelerates set

ASTM C 494 or AASHTO M 194ASTM C 494 or AASHTO M 194


Water Reducer and Slump Loss


Retardation (Initial Set)


Retardation (Final Set)


Mid-Range Water Reducing Admixtures

Reduce water content 6% to 12%

Reduce cement content Reduce water-cement ratio No retardation Improve placeability and

finishability


High-Range Water-Reducing Admixtures

Reduce H2O content 12% -30% Reduced W/C produces conc.

with: Compressive Strength > 70 MPa Increased early strength gain Reduced Cl ion penetration

ASTM C 494 or AASHTO M 194 ASTM C 494 or AASHTO M 194

Type F― Water Reducing

Type G ― Water Reducing and Retarding


High-Range Water Reducer and Slump Loss


HRWR, Water Reducer and Air Loss

0.048825.66.8B0.065593.86.4M0.040714.86.8NHigh-range

water reducer

0.040744.66.2H0.038674.77.0LWater

reducer

0.020563.05.4CControlMixture

Rate of air loss,

%/minute

Percent air

retained

Final air content,

% *

Initial air content,

%

*at point where slump falls below 25 mm


Compressive Strength Development


Plasticizers for Flowing Concrete

Essentially High-Range Water Reducer

SuperplasticizersAlso known as ―

ASTM C 1017Type 1 ―Plasticizing

Type 2 ― Plasticizing and Retarding


Plasticizers for Flowing Concrete

Produce flowing concrete with high slump ( 190 mm [7.5 in.])

Reduce bleeding

Extended-slump-life plasticizer reduces slump loss.

ASTM C 1017ASTM C 1017

Superplasticizers


Flowing Concrete


Flowing Concrete as Thin Overlay


Flowing Concretes and Slump Loss


Retardation of Flowing Concrete (Initial Set)


Retardation of Flowing Concrete (Final Set)


Compressive Strength Development in Flowing Concrete


Bleeding of Flowing Concrete


Retarding Admixtures

Delay setting or hardening rate for:

Hot-weather concreting Difficult placements Special finishing processes

ASTM C 494 or AASHTO M 194, Type BASTM C 494 or AASHTO M 194, Type B


Slump Loss at Various Temperatures


Accelerating Admixtures

Accelerate the rate of: Hydration (setting) Early-age strength gain

ASTM C 494 or AASHTO M 194, Type CASTM C 494 or AASHTO M 194, Type C

Calcium chloride accelerators: Increase drying shrinkage,

potential reinforcement corrosion, potential scaling

Darken concrete


Maximum Chloride-Ion Content

0.30Other reinforced concrete construction

1.00Reinforced concrete that will be dry or protected from moisture in service

0.15Reinforced concrete ex-posed to chloride in service

0.06Prestressed concreteType of member

Maximum water soluble chloride-ion (CI¯) in

concrete, percent by mass of cement


Corrosion Inhibitors

Control Corrosion of Steel Reinforcement

Dosage dependent on anticipated chloride level


Shrinkage-Reducing Admixtures


ASR Inhibitors—Lithium Carbonate


Coloring Admixtures (Pigments)


Liquid Admixture Dispenser


Videos 1/2

Air-Entraining Admixture Water Reducer


Videos 2/2

Retarder/Accelerator Admixture Dispenser

admixtures for concrete - college of · pdf fileair-entraining admixtures water-reducing...

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