Properties of Fresh Concrete

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 :

àDefinition: 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:

àSlump 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:

àConsistency 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.