9.4 : 高性能減水剤

Superplasticizers are used to prepare fluid concrete that can be easily placed in dense reinforcement arrangements within a mold or for quick placement in floors and pavements.

Some superplasticizers are typically sulfonated melamine formaldehyde or sulfonated naphthalene formaldehyde condensate, with a dosage of about 0.2 to 0.6 gallons per cubic yard of concrete.

Superplasticizers enhance cement dispersal by causing sulfonic acid to be absorbed onto cement particle surfaces, which become negatively charged and repel each other.

This action improves the concrete's workability for the maintained water-cement ratio, often increasing the slump from 3 to 8 inches.

Fine aggregate is increased by 4 to 5 percent for flowing concrete, and elongated, flaky, or very angular aggregates are avoided to prevent segregation and bleeding.

It is important to consider that such concrete can exert hydrostatic pressure in formwork.

Superplasticizers can reduce water usage by 25 to 35 percent, allowing for low water-to-cement ratios and enabling concrete to reach strengths up to 15,000 psi in 28 days.

Superplasticizers are added to concrete right before concrete placement because enhanced workability from superplasticizers is temporary.