NASCLA Accredited Commercial General ContractorConcreteHard
A construction crew is placing concrete for a heavily reinforced column. To ensure proper consolidation and eliminate air voids around the rebar, which type of vibrator is most appropriate for this application?
- ASurface vibrator (e.g., vibrating screed).
- BExternal form vibrator.
- CTable vibrator.
- DInternal (spud) vibrator.
Show answer & explanationAnswer & explanation
Correct answer: D. Internal (spud) vibrator.
Internal (spud) vibrators are the most effective and commonly used type for consolidating concrete in heavily reinforced elements like columns and walls. Their ability to be inserted directly into the concrete allows for thorough compaction and removal of entrapped air, especially around rebar.
Why the other options are wrong
- A. Surface vibrators are suitable for thin slabs and pavements, not for deep, heavily reinforced columns where internal consolidation is required.
- B. External form vibrators are used for thin walls or precast elements where internal vibrators cannot be used, but they are less effective than internal vibrators for dense reinforcement.
- C. Table vibrators are used for precast concrete elements in a factory setting, not for in-situ placement of columns.
Internal Concrete Vibrator
A type of vibrator consisting of a vibrating head inserted directly into fresh concrete to consolidate it.
- Most common type for structural concrete.
- Removes entrapped air and ensures dense concrete.
- Requires systematic insertion and withdrawal.
Memory trick: Internal deep, External thin, Surface wide, Hand for small.