How do you select the needle size for a vibrator?

Selection depends on the spacing of the reinforcement and the formwork dimensions; the needle must pass freely between rebars without getting stuck.

What is the recommended frequency for concrete internal vibrators?

Generally between 8000 and 12000 vibrations per minute (vpm), sufficient to fluidize the concrete mix.

How long should the vibrator be immersed?

Typically 5 to 15 seconds per insertion, or until a thin film of mortar appears on the surface and large air bubbles stop escaping.

IS 2505

: 1992

Concrete Vibrators, Immersion Type (Internal Vibrators) - Specification

CurrentSpecializedSpecificationGeneral · Scaffolding, Formwork and Construction Equipment

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This standard specifies the requirements for materials, sizes, construction, and performance of immersion type (internal) concrete vibrators used for compacting concrete on construction sites.

Specifies requirements for immersion (poker) type concrete vibrators.

Quick Reference Values

Nominal sizes of vibrator needles25, 40, 60 mm (typically)

Typical operating frequency8000 to 12000 vibrations per minute (vpm)

Typical amplitude of vibration0.5 mm to 1.5 mm

Practical Notes

Do not use the vibrator to push or move concrete laterally, as this causes segregation.

Insert the needle vertically and quickly, and withdraw it slowly to allow entrapped air to escape without leaving a void.

The needle should be kept at least 50 mm away from the formwork to prevent damage to the forms and surface blemishes.