Fresh concret

Properties Of Fresh Concrete – Segregation And Bleeding

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Fresh concrete made from aggregates, cement, and water has some properties. The properties of hardened concrete highly depend on the properties of fresh concrete. Some of the properties of fresh concrete are discussed below.

Segregation

It is the property of fresh concrete in which some of the constituents like aggregate settle down to the bottom. It happens because of excess water in the mix design of the concrete. Also, more than the required mixing time leads to the segregation of constituents of concrete. Over-compaction with the vibrator is also one of the reasons for segregation. In the case of ready mix concrete, this is a common issue.
The remedial measure to segregation is to remix the concrete before placing it.

Bleeding

After placing the concrete, it shows free water on the top surface. It’s called bleeding. If the rate of water evaporation from the surface and the rate of bleeding is the same, then there won’t be any issues.
Bleeding makes concrete porous and ultimately reduces the strength of hardened concrete. One way to avoid bleeding is to remix the concrete.

bleeding after casting of concrete slab
bleeding after casting of concrete slab.

Loss of slump

It is also called loss of workability. It is measured by the slump test.

Workability

Workability means to ease in work with flow concrete. If the concrete has good workability, then compaction could be done easily. Also, workable concrete is a need to convey concrete with the pipe.
Workability could be measured with compacting factor test or slump test. To maintain the concrete workable for long time plasticizers and superplasticizers are used.

Plastic shrinkage

Concrete gets shrinkage after hardened. This is because while setting water is used in the hydration of cement in the concrete. So, after drying volume of concrete gets shrunk. This could be avoided by using low-heat cement.
Also read
Types of Cement, Their Properties and Applications
Water Cement Ratio – Explained In Detail



Also read
Admixtures of Concrete (Concrete technology)

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