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Chapter: Civil - Construction Materials: Concrete

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Properties of Fresh Concrete

Properties of Fresh Concrete
The first 48 hours are very important for the performance of the concrete structure.

Properties of Fresh Concrete:

 

Significance:

 

The first 48 hours are very important for the performance of the concrete structure.

 

It controls the long-term behavior, influence f'c (ultimate strength), Ec (elastic modulus), creep, and durability.

 

Properties of Fresh Concrete :

 

Properties at Early Ages :

 

       Workability

 

       Slump Loss

 

       Segregation/Bleeding

 

       Plastic Shrinkage

 

       Time of Set

 

Workability :

 

Definition: Effort required to manipulate a concrete mixture with a minimum of segregation.

 

It is not a fundamental property of concrete.

 

I) consistency (slump)-- easy to flow

 

II) cohesiveness --tendency to bleed and segregate

 

Slump Test:

 

Slump test is a test conducting before concrete to be used for casting. The purpose of slump test Is to determine the water content in concrete and its workability


Consistency:

 

Consistency or fluidity of concrete is an important component of workability and refers in a way to the wetness of the concrete.

 

However, it must not be assumed that the wetter the mix the more workable it is. If a mix is too wet, segregation may occur with resulting honeycomb, excessive bleeding, and sand streaking on the formed surfaces.

 

On the other hand, if a mix is too dry it may be difficult to place and compact, and segregation may occur because of lack of cohesiveness and plasticity of the paste.

 

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