How to Reduce Bleeding in Concrete?

Bleeding is the development of a layer of water at the top or surface of freshly placed concrete. The cause of bleeding is the settlement of solid particles (such as cement and aggregates) and the simultaneous upward migration of water. It is worth noting that some bleeding is normal and will not reduce the quality concrete if it is properly placed, finished, and cured.

However, excessive bleeding will increase the water-to-cement ratio in the upper concrete layer near the top surface. This creates a weak top layer with poor durability properties, especially if the finishing operations happen while bleed water is present.

Methods to Reduce Bleeding in Concrete

1. Reduce the water content (water-to-cementitious material ratio) and slump.
2. Increase the amount of cement resulting in a reduced water-cement ratio.
3. Use cementitious materials with finer particles.
4. Increase the amount of fines in the sand.
5. Use or increase the amount of supplementary cementing materials such as fly ash, slag cement, or silica fume.
6. Use chemical admixtures that permit reducing the water to-binder ratios or provide other means capable of reducing the bleeding of concrete.
8. Use air-entrained concrete.

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