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Here's some links to our Grace admixtures available for use in our concrete:


Daravair 1400 (Air entrainment)

ADVA 140 (Water Reducer)

Recover (Retarder / Hydration Stabilizer)

Polarset (Accelerator-Non-Chloride)

Daraccel (Accelerator-contains chlorides)

READ ON (scroll down) for some more general information about admixtures for concrete.

Chemical Admixtures


Admixture Defined

§    A material other than water, aggregates, cementitious materials and fiber used as an ingredient in concrete or mortar and added to the batch immediately before or during mixing.

§    Typically in liquid form and small amounts.

Admixtures in FRESH concrete:  

§     Increase workability without adding water

§     Reduce water requirements

§     Accelerate or retard setting times

§     Reduce bleeding

§     Control cement hydration

§     Compensate for slump loss

§     Improve pumpability

§     Reduce Segregation

§     Improve finishability


Admixtures in HARDENED concrete used to:

§     Entrain air

§     Increase early age strength

§     Increase ultimate potential strength

§     Decrease permeability

§     Reduce potential for corrosion of steel

§     Reduce heat of hydration

§     Reduce expansion produced by alkali-aggregate reaction

§     Increase resistance to environment

Specification Classes

§    ASTM C 494, Chemical:

§   Type A:  Water Reducing

§   Type B:  Retarding

§   Type C:  Accelerating

§   Type D:  Water reducing & retarding

§   Type E:  Water reducing & accelerating

§   Type F:  High range water reducers(HRWR)

§   Type G: HRWR and retarding

Specification Classes

§    ASTM C 260:  Air Entraining Admixes

§    ASTM C 1017: Flowing Concrete

§   Type I:  Plasticizing

§   Type II: Plasticizing & retarding

§    ASTM D 98:  Calcium Chloride Admixes


Water Reducing Admixes

§          Breaks up agglomerations of statically charged cement particles spreading out the grains in    fresh concrete freeing up more water and allows for more efficient hydration. 

§           Strength increases are evident with the use of water reducers at same H2O/cement ratio
§      Used to increase workability.

§      Can increase slump by 2 or more inches.

§      Can also use to solely reduce water ultimately increasing strength.

§      If increase in strength is not necessary, corresponding amount of cement may be reduced from the concrete mixture…most common use

§      Improves pumpability

§      Hot weather…water reducers can be added to make up for the increase in water demand caused by higher temperatures.

Water Reducing Admixes (Composition)

§    Salts of lignosulfonates (by products of the wood processing industry), hydroxylated carboxylic acids, and polymers (manufactured/refined chemicals).

§    Acts as a retarder and will often have a small amount of accelerator blended to offset the retarding effect.

Water Reducing Admixes

§     Commonly added to the batch through the batch water line. 

§     In extreme cases, higher doses may be needed and the admix should be added after the cement has wetted (delayed addition).

§     Overdoses will most often cause retardation and in some cases may not set for days.

High-Range
Water Reducing Admixes

§    “Superplasticizers” allow for significant amounts of water reduction without excessively retarding the set time.

§    12% to 40% reduction of water!

§    Used in same fashion as water reducers

§    Can produce “flowing” concrete…take an initial 3” slump to a 6” without affecting water/cement ratio

High-Range
Water Reducing Admixes

§     If cement held constant, superplasticized concrete will have higher early-strengths and reduced permeability.

§     Only have effect for discrete period of time, after which time the concrete loses the “extra” slump or workability.  May add at plant or at jobsite if time of travel is an issue.

§     May be used in combo with water reducers to help offset slump loss in high cement mixes.

Mid-Range Water Reducers

§    Do not retard set times or entrap air

§    Used at a 5 to 8 inch slump

§    Can improve the finishing characteristics of “sticky” concretes that contain silica fume or manufactured sands.

§    Superior workability, pumpability, and finishability.

Accelerating Admixtures

§    Reduce set times and accelerates early-age strength gain of hardened concrete.

§    Can reduce time and labor costs.

§    Calcium chloride (2% of wt of cement) or NCA  depending on situation.  Chlorides contribute to corrosion of steel.

Retarding Admixtures

§     Used to offset the effects of higher temperatures on concrete that cause concrete to set and lose slump at a fast rate.

§     Delay initial set by an hour or more.

§     Reduce possibility of unplanned construction or “cold” joints.

§     Made of lignosulfonates and/or carbohydrates such as molasses, corn sugar, or others.

§     Most water reducers retard setting and so “water-reducing retarders” are typically used.

Air-Entraining Admixtures

§    “Laundry Detergents” produce millions of bubbles which protects concrete from damage in freezing and thawing.

§    “Entrapped air” from mixing do not help like the “entrained air” bubbles.

§    Proper vibration and consolidation will remove most of the entrapped air.

§    Measured “air content” includes both!

Effects of Entrained Air

§    Increases slump and improves workability.

§    Reduces segregation.

§    Improves finishing characteristics making concrete easier to smooth and trowel.

§    Slows bleeding rate by “blocking” water passageways.

§    Reduces the amount of water needed.

Entrained Air-continued

§    Interior concrete not subject to freezing and thawing do not need air entrainment, unless exposed during construction.

§    Air should be avoided (or reduced) with hard trowelled finishes and with dry shakes, as delaminations will occur.

Entrained Air--content

§    Made from salts from wood oils or resin, natural resins, or synthetic detergents.

§    Formed through mixing action.

§    Usually air makes up 5 to 8% of volume.

Effects on Entrained Air dosage:

§    The effects of continued mixing and the delivery time must be considered.

§    Air temperature, temperature of materials…more air will be needed in the summer to produce same air as in winter.

§    Cement and aggregate characteristics.

§    Other admixtures.

Air Entrainment-Advantages:

§    Necessary for freeze/thaw durability

§    Increase yield

§    Improved workability and pumpability

§    Reduced segregation and bleeding

§    Reduced permeability

§    Improved finishing with harsh sands.

Air Entrainment-Disadvantage:

§    Strength of concrete is reduced as air content increases.

§    Increases air by 1% may decrease strength by approximately 5% of the strength.

Factors Affecting Air Content of Concrete

§    Alkali content of cement: air content will increase when alkali increases.

§    Cement fineness:  increase in fineness will tend to decrease the air content

§   Finer cement = more air needed!

§    Cement content: increased cement will result in decreased air content.

Factors Affecting Air Content of Concrete (cont)

§    Fly Ash: use of fly ash will increase the amount of AEA needed.

§    Ground Granulated Blast Furnace Slag:  typically slag is finer than cement and will require a higher AEA dosage.

§    Silica Fume: increased silica fume will decrease the air content.  For mixes with 10%, AEA dosage may increase 100%.

Factors Affecting Air Content of Concrete (cont)

§     Maximum aggregate size:  recommended air content will decrease as the coarse aggregate size increases. 

§    Reduces mortar fraction

§     Sand-to-total aggregate ratio:  higher sand fraction promotes increase in air content.  More sand = more natural air

§     Sand grading:  finer sands require higher dosage of AEA.

Factors Affecting Air Content of Concrete (cont)

§    Water reducing and retarding admixtures (lignin based):  increased water reducers or reducers will increase the air content, thus decreasing the amount of AEA.

§    Accelerators:  minor effects.

§    High range water reducers:  higher air.

§    Mixing Water:  Harder water will require more AEA.

Factors Affecting Air Content of Concrete (cont)

§     Water-Cement Ratio: higher water to cement ratio generates a higher air content.  At higher water/cement ratios the air void spacing increases and larger air bubbles will be formed.

§     Slump:  as slump increases, air increases.  Increasing air content will also increase the slump.

§    Water added on the jobsite will pose a problem, as a small amount added can cause a significant increase due to an increased generation of air.

Production procedures effect on Air Entrainment:

§      Batching cement prior to AEA generates a higher air content.

§      Cement and aggregates ribboned together will produce higher air content.

§      AEA should be batched on the sand in the weigh hopper or in the water line in the initial portion of the load.

§      Air content increases as the size of the load approaches mixer capacity.

§      Blade wear and buildup will reduce mixing effect, thus reducing air content.

§      Prolonged mixing will increase air.

§      High energy or excessive mixing will decrease air content.

§      Higher concrete temperatures will require a higher dose of AEA.

Admixtures (misc)

§            Corrosion inhibitors:  reduces or delays the onset of corrosion of steel.

§            Hydration stabilizers: “super retarders” stop hydration of the cement.  Used for “reuse” of concrete, or stabilizing truck mixer wash.  Also for long hauls.

§            ASR Protection: reduces effects of ASR

§            Gas forming and foaming agents: used to make cellular and lightweight concrete used as a substitute for backfill.

Admixtures (misc)

§             Damp-proofing: used on some slabs on grade and in some areas where exposed concrete roofing systems are used.

§             Shrinkage reducing: reduces shrinkage cracking by reducing surface tension of the water in the pores of the cement paste in concrete.

§             Coloring: integral or dry shake methods.

§             Viscosity modifying: make fresh concrete more cohesive and less susceptible to segregation.  Used in underwater applications and in self-consolidating concretes (self leveling and do not segregate at high slumps.)

ADMIXTURE     TYPICAL USAGE

§       WATER REDUCERS:          IMPROVE STRENGTH & CEMENT EFFECIENCY

§       RETARDERS:          EXTEND SET TIME ESPECIALLY IN HOT WEATHER

§       ACCELERATORS:          REDUCE COLD WEATHER PROTECTION NEEDS

§       ACCELERATOR:          REDUCE CYCLE TIME

§       MRWR:                      INCREASE FINISHABILITY AT HIGHER SLUMPS

§       HRWR:                       AVOID SEGREGATION AT HIGH SLUMP

§       HRWR:                       REDUCE LABOR COST AND PUMP PLACEMENT

§       HRWR:                       STRUCTURAL FLOWABLE CONCRETE

§       HRWR:                       AVOID SITE ADDED WATER

§       HRWR:                       HIGH STRENGTH CONCRETE

§       HRWR:                       FOR PLACING IN CONGESTED AREA

§       SILICA FUME:          ULTRA-HIGH STRENGTH CONCRETE

§       SILICA FUME:          DENSER CONCRETE—RESIST CHEMICAL ATTACK

§       CORROSION INHIBITOR:          PROTECT AGAINST CORROSION

§       EXTENDED SET ADMIXES:          WASH-OUT AND RECYCLING CONCRETE

SYNTHETIC FIBERS

§    Nylon and polypropylene commonly used

§    Monofilament and collated fibrillated type

§    Used for secondary reinforcement, while steel fibers can be used for primary

SYNTHETIC FIBERS--APPLICATION

§    Reduces tendency of shrinkage cracking

§    Blocks crack growth in low strength concrete prior to setting

§    Reduce bleeding, thus permeability, and an increase in ductility and impact resistance

§    Slight reduction in slump may be seen:

§   Increase water reducers, not water amount

Admixture Batching

§    Liquid admixtures are metered into graduated cylinders called “admixture bottles”

§    Based on “Ounces per 100 lb cement”

§    Tolerance is +-3% of target quantity

§    “Straight-through” systems meters admix directly into a batch to facilitate production in high dosage applications

Admixture Batching

§    Liquid admixtures are usually batched with the mixing water or onto the fine aggregate.

§    Avoid intermingling admixes during mixer charging.

§    Plant operator should check dispensers and lines to ensure accurate and consistent batching!