What Special Performance Do You Need?

Source:www.stonediamondtool.com Date:2019/1/15 Read:337

Protect Against Freeze Thaw Cycles Improve Durability

Air entrainment is particularly effective in providing resistance to freeze-thaw cycles. When the moisture in concrete freezes, these air cells relieve internal pressure by providing microscopic chambers for the expansion of water as it freezes.

Some air entraining mixtures contain a catalyst for more rapid and complete hydration of portland cement.

To protect concrete from damage during freezing, bubbles must have the proper size, distribution and volume. ASTM C 260 specifies requirements for air entraining admixtures.

Benefits of air-entrainment include:

· Improved resistance of concrete to severe frost action or freeze/thaw cycles

· High resistance to cycles of wetting and drying

· High degree of workability

· High degree of durability

Dosage: Typical air entrainment ranges from 5% to 8% of the volume of concrete.

Water Reduction in the Mix

Water reducers have become so important in concrete, that they could be considered the "fifth" ingredient.

They can be used to: (1) increase slump, (2) lower the water-cement ratio, or (3) reduce cement content.

Water reducers come as Low Range, Mid Range, and High Range Superplasticizers. There are enough different admixtures available that it is possible to select one that meets the need of a particular project whether it is tall columns that need a mix that pumps easily, or an easy-to-finish durable floor slab.

In general, they provide the required slump with less water in the mix, and may provide higher strength concrete without increasing the amount of cement.

Conventional water reducers

Are required to achieve a minimum 5% water reduction. A conventional water reducer can reduce slump by about 1 to 2 inches without the addition of water.

Mid-Range water reducers

Can reduce water content by at least 8% and as much as 15%. They tend to be stable over a wider range of temperatures and tend to give more consistent setting times. These reducers work most effectively in mixes designed to have a slump in the range of 4 to 5 inches.

Particularly useful in hot weather concreting by counteracting the accelerating effect of high ambient and concrete temperatures

Slow the setting rate of concrete

Delay initial set of concrete

Keep concrete workable during placement

High-Range water reducers (superplasticizers)

Can reduce water content from 12% to as much as 40% and are typically used in concretes designed to have slumps of 8 to 11 inches. They can be used to either increase slump (by 4 to 8 inches) or lower the water content of hot weather concrete mixes. Used to increase flowability. You can also read frequently asked questions about superplastisizers on the Fritz-Pak website.

High Strength Concrete

Admixtures containing microsilica (condensed silica fume) are used to meet high strength and low permeability requirements.

Benefits include reduced permeability, increased compressive and flexural strengths, and increased durability.

Applications include high-strength structural columns, less permeable parking garage decks, and abrasion resistant hydraulic structures.

Silica fume can be used in concrete to produce compressive strengths approaching 20,000 psi under jobsite conditions. This admixture can be added in a slurry or in a dry form, whichever meets the batching equipment needs. In either case, performance is the same.

Strength Enhancement

Concrete strength enhancement can be achieved through use of superplasticizer admixtures to produce a low water/cement ratio giving high performance concrete.