High range water reducing admixture reduces the quantity of mixing water required to produce concrete of a given consistency by 12 % or greater, as per ASTM C 494- C 494M. It is capable of producing great water reduction, great flowability, or both.
High range water reducing admixture can reduce the water-cement ratio while maintaining slump, increase slump while maintaining a constant water-cement ratio, or reduce the cementitious materials content and water content while maintaining constant slump and strength.
Slump loss characteristics of the concrete would determine whether the high range water reducer should be introduced at the plant, at the site, or both locations. Matching the chemical admixture to the cementitious materials, both in type and dosage rate is important.
High range water reducing admixture is used to produce high strength concrete to reduce cross section of compression members in high rise building, improve durability of concrete in aggressive environments, and many more applications.
Types
- Sulfonated melamine-formaldehyde condensates.
- Sulfonated naphthalene-formaldehyde condensate
- Modified lignosulfonates.
- Polycarboxylate derivatives.
Influences on Concrete Properties
- It improves concrete workability without bleeding and segregation
- Increase concrete strength
- Drying shrinkage of concrete can be decreased.
- If properly cured, permeability of concrete in which high range water reducing admixture is used is greatly reduced, in turn, penetration of aggressive agents is declined.
- It enhances concrete bond strength
Advantages
- High range water reducers may serve the purpose of increasing strength through a reduction in the water-cement ratio while maintaining equal slump, increasing slump while maintaining equal water-cement ratio or a combination thereof.
- It declines concrete permeability and increase its durability.
- High range water reducing admixture decreases the quantity of cement needed to gain specific strength.
Mix Precautions
The method of addition should distribute the admixture uniformly throughout the concrete. Adequate mixing is critical to uniform performance. Problems resulting from non-uniform admixture distribution or batch-to-batch dosage variations include inconsistent slump, rate of hardening, and strength development.