The time window for a superplasticizer to increase workability is

The time window for a superplasticizer to increase workability is

• A. 15 to 30 minutes
• B. 30 to 45 minutes
• C. 30 to 60 minutes
• D. 45 to 90 minutes

Answer: (C)

Superplasticizers boost workability by dispersing cement particles, letting you maintain a lower water–cement ratio without sacrificing flow. This effect is most reliable while the concrete is still plastic and before substantial hydration progresses, so there is a practical window to adjust slump. In typical practice, you can add or re-dosage a superplasticizer to regain or increase workability about 30 to 60 minutes after mixing. If you wait much longer, the mix begins to stiffen and the additive’s impact diminishes; adding too early (like 15–30 minutes) can lead to inconsistent performance relative to placement timing, while waiting beyond roughly an hour often won’t restore the desired workability. Hence, 30 to 60 minutes is the best-fitting window.

Superplasticizers boost workability by dispersing cement particles, letting you maintain a lower water–cement ratio without sacrificing flow. This effect is most reliable while the concrete is still plastic and before substantial hydration progresses, so there is a practical window to adjust slump. In typical practice, you can add or re-dosage a superplasticizer to regain or increase workability about 30 to 60 minutes after mixing. If you wait much longer, the mix begins to stiffen and the additive’s impact diminishes; adding too early (like 15–30 minutes) can lead to inconsistent performance relative to placement timing, while waiting beyond roughly an hour often won’t restore the desired workability. Hence, 30 to 60 minutes is the best-fitting window.