Category: Structure & materials
Prepared by Eng. Ahmed Fathy, Projects Manager ·
Definition
A vibrator is a poker inserted into fresh concrete that vibrates rapidly, driving out air bubbles so the concrete fills the forms and wraps the steel. It goes in vertically at close spacing for a few seconds, then is withdrawn slowly.
Why it matters on a project
Too little vibration leaves honeycombing and voids around the steel; too much separates aggregate from paste. Keep a spare vibrator on site on pour day.
Common mistake
Using the vibrator to push concrete sideways through the forms instead of placing it where needed, which segregates the mix.
Frequently asked questions
How long should the vibrator stay in?
Until bubbles stop and the surface glistens, usually a few seconds per point.
Should the poker touch the steel?
Avoid it where possible, especially near concrete that has started to stiffen.
Related terms
- Concrete pumpPlant that pumps ready-mix concrete through pipes to the pour.
- Slump testA simple site test measuring the consistency and workability of fresh concrete.
- Pre-pour checklistChecking steel, formwork and services before a pour is approved.
- Concrete cracksCracks in concrete from structural or non-structural causes.
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