Verifi Concrete Quality Blog

Posts Tagged ‘admixture’

Types of Water Reducing Admixtures

by Verifi

Verifi can automatically add water-reducing admixtures to concrete in the truck to maintain slump.

 Choosing the right types of water reducing admixtures is important. A wide array of water-reducers is commercially available and can be categorized as follows.

Performance

ASTM C494, the standard specification for chemical admixtures for concrete, defines water reducers based on the amount of water reduction and corresponding effects on setting time, compressive strength, flexural strength, shrinkage, and freeze-thaw durability.

  • Water Reducing Admixture: water reduction of 5% or greater

  • Mid-Range : Although not defined in ASTM C494, most chemical admixture companies market this category

  • High-Range: water reduction of 12% or greater

 The terms superplasticizer and high-range water reducing admixture (HRWRA) can be used interchangeably.

Chemistry

The most common types of chemistry used in water reducers include:

  • Lignosulfonate

  • Sugars/Sugar Acids, such as molasses, corn syrup, and gluconate

  • Melamine Sulfonate Formaldehyde Condensate (MSFC)

  • Naphthalene Sulfonate Formaldehyde Condensate (NSFC)

  • Polycarboxylate Ether (PCE)

 Normal-RangeMid-RangeHigh-Range
LignosulfonateXX
Sugars/Sugar AcidsXX
MelamineX
NaphthaleneX
PolycarboxylateXX

Most commercially available admixtures are a formulation of multiple chemical ingredients. The above types of chemistries can be blended together or with other chemical ingredients to achieve performance characteristics such as delayed or accelerated setting time, controlled air content, increased finishability, or enhanced rheology.

 Brand Name

Admixtures suppliers market admixtures under different brands, each representing different performance categories. Several products may be sold under each brand, each tailored to different applications.

Grace: WRDA®, Zyla®, Mira®, Daracem®, ADVA®
BASF: Pozzolith®, Polyheed®, Rheobuild®, Glenium®
Sika: Plastiment®, Sikament®, Viscocrete®

 Selecting Admixtures for Verifi

Verifi recommends the use of polycarboxylate-based superplasticizers. These are the latest generation of superplasticizers and can be engineered at the molecular level for specific performance, such as effects on setting time and early age strength.

When the correct polycarboxylate-based superplasticizer is chosen, the dose can be varied as conditions change to maintain a consistent slump at discharge, while also ensuring consistent setting time, air content, and strength development.

 

Admixture in Transit: What Contractors Need to Know

by Verifi

Concrete producers can use Verifi to add concrete admixtures, such as superplasticizer, to the truck to maintain slump from batching to discharge. Concrete admixtures can be added in transit, so that the concrete arrives on site at the ordered slump and ready to pour. Here are a few things to keep in mind when pouring concrete with Verifi admixture additions.

  1. Superplasticizers increase slump without reducing concrete quality. You can get the slump you want without reducing strength.

  2. Ask for higher slump, not more water. When the slump is lower than desired, most contractors ask for more water: “Give me 20 gallons!”  For concrete trucks with Verifi, ask for higher slump. Verifi will automatically calculate and add the right amount of water or admixture to add to provide the slump you request.

  3. Admixture choice matters. Concrete producers have access to numerous admixtures to help tailor concrete performance to the application. Admixtures are selected based on factors including setting time, strength development, pumpability, and finishability. The right admixture can make a huge difference.  Likewise, the wrong admixture can make for a miserable experience. Verifi works closely with concrete suppliers to select the right admixture.

  4. Ensure concrete is mixed after superplasticizer addition. Superplasticizers require a certain number of revolutions to be fully mixed into the load. Verifi shows the driver the amount of mixing required to ensure concrete is fully mixed. This mixing can occur during transit at agitation drum speed. If done at the jobsite at high drum speed, mixing typically requires 2 minutes or less.

  5. Expect consistent setting time. Adding water to concrete delays setting time. Superplasticizers can be chosen to increase slump without affecting setting time.

  6. Expect better pumpability and finishability. Additions of superplasticizer typically result in better concrete rheology than mixes with water added, which means concrete is less likely to segregate and is easier to pump and finish.

concrete admixtures in transit Verifi

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