Retarder

1. Delay onset of setting and hardening i.e extending the time between initial mixing and final compaction
2. Use in how weather where large concrete pour
3. Frequently used in ready-mixed concrete
4. Uses influenced by aggregate type and grading
5. Do not adversely affect 28-day strength
6. Adverse affect : increase bleeding with some types , increase drying shringkage , reduction early - strength development