Bleeding is considered acceptable to a limited extent if it occurs when the concrete is:
Correct Answer: C. Plastic
📚 Detailed Explanation: Minor Bleeding Acceptable Only in Plastic State
Why C (Plastic) is correct: Bleeding (upward migration of free water to the concrete surface) is a natural phenomenon caused by the settlement of solids in the fresh concrete. A very small degree of bleeding while the concrete is still plastic (freshly placed, still fluid) is acceptable — it slightly lubricates the surface for screeding and floating. However, excessive bleeding is always harmful.
Bleeding at Different Stages
| Stage | Bleeding Effect | Acceptability |
|---|---|---|
| During transport | Water rises in the transit mixer drum or truck | Undesirable — alters w/c ratio; causes segregation if severe |
| During mixing | Water visible on surface immediately after mixing | Indicates too high w/c; undesirable |
| Plastic state (freshly placed) | Minor water film on surface; concrete still workable | Tolerable in small amounts; helps surface finishing |
| After initial set | Water trapped below aggregate; capillary channels form | Undesirable — creates permeable channels after drying |
Consequences of Excessive Bleeding
| Effect | Detail |
|---|---|
| Laitance formation | Weak layer of cement paste and fines on top surface; easily dusts off |
| Increased permeability | Bleed water channels remain as capillary voids after drying |
| Bond reduction | Water collects under reinforcement bars and under aggregate particles → weak interface zones |
| Reduced surface strength | Top layer has higher w/c (diluted) → lower strength than the rest of the section |
- Minor bleeding in the plastic state only is acceptable; excessive bleeding is always harmful.
- Never trowel bleed water back into the surface — wait for it to evaporate first.
- Reduce bleeding by: lower w/c ratio, use of finer cement, air entrainment, or reducing water content.