Technical Questions

ACI Committees, Membership, and Staff have answered common questions on a variety of concrete related topics.



Does over-vibration cause segregation and loss of air content?

Q. Does over-vibration cause segregation and loss of air content?

 

A. Normal-density concretes that are well-proportioned and have adequate consistency are not readily susceptible to segregation resulting from over-vibration (ACI 309). A mixture with excess mortar is prone to segregation when over-vibrated, however. A well-proportioned mixture with the proper air-void system will lose some air during vibration. The system will still provide satisfactory resistance to freezing and thawing because the loss of air will be from large-size bubbles and it will not increase the bubble-spacing factor beyond acceptable limits.

 

References: SP-1(02); ACI 309R-05

Topics in Concrete: Concrete Fundamentals; Consolidation; Placing

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