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.

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