Key Factors Affecting Gypsum Plaster Setting Time and How to Control It
Created on 08.18
Why Does Setting Time Become Unstable?
Gypsum plaster is valued for its lightweight, insulation, energy efficiency, and eco-friendly properties. However, in practice, unstable setting time often creates problems:
- Too fast
→ not enough working time for application;
- Too slow
→ cracking or powdering of the surface.
Main Causes
- Over-burned gypsum
→ Excess anhydrite causes shorter setting, later extended after aging.
- Under-burned or moisture-exposed gypsum
→ Hemihydrate converts to dihydrate, shortening setting.
- Environmental conditions
→ Heat and wind accelerate water loss, reducing setting time.
- Unstable retarders
→ Low-quality additives lead to inconsistency.
- No raw material testing
→ Fixed retarder dosage without testing causes unpredictable results.
Solutions
- Raw Material Control
Age gypsum for 1–2 weeks until stable; store in a dry, sealed place.
- Construction Environment
Avoid working in extreme heat, strong wind, or freezing conditions.
- Retarder Selection
Use stable, reliable retarders from trusted brands to minimize variations.
Conclusion
By controlling raw materials, environment, and retarders, unstable setting time can be avoided, ensuring:
- Better workability
- Higher efficiency
- More durable wall finishes
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