fresh concrete
• To ensure that the hardened concrete is acceptable in operation, the concrete must meet the following
• 1. Mix and transportation
• 2 . Must be uniform throughout the batch and between batches
• 3 .
Must circulate properly completing the forms • 4
. Must be able to be fully compacted without excessive energy,
• 5. Should not separate when laying and compaction
• 6 . Must be completed , nature or formwork
Properties of fresh concrete
• Introduction • The potential strength and durability of concrete from a report given mixture is highly dependent on the degree of compaction .
• It is essential , therefore, that the consistency of the mixture is such that the concrete can be transported, placed , and finished with early enough to reach the expected strength and durability.
Properties of fresh concrete
Importance • • The first 48 hours are very important for the performance of the concrete structure . • Controls the behavior in the long term, f'c influence ( tensile strength ) , Ec ( module) , creep and durability.
Properties of fresh concrete
Properties in Upper Age • Handling slump loss • • Separation / Bleeding • Plastic • Operating Temperature • Withdrawal
Properties of fresh concrete
• Machining • Definition: to manage a concrete mixture with a minimum of segregation efforts.
• It is a fundamental property of concrete .
Properties of fresh concrete
• If the compacting is achieved by vibration or Raming , the method consists essentially remove entrapped air in the concrete until it has reached a densest possible configuration for a given mixture . • large air pockets trapped seriously weaken the concrete act as powerful as stress concentrations .
Workability and consistency
• It was noted that the ability to work is a patented compound with at least two main elements: • a. Consistency he describes as " easy flow " . . Concrete and b • Cohesion he describes as " the tendency to bleed or segregate " • Among the important factors that affect the workability of concrete are :
consistency
• Consistency or the fluidity of the concrete is an important part of the working capacity and refers to a form of concrete moisture . • However, it should not be assumed that the wet mixture is easier. If the mixture is too wet , segregation can occur with resulting honeycomb , excessive bleeding and sand streaks formed on
the surfaces
