How long should an immersion vibrator be held in one spot?

Usually 5 to 15 seconds, until air bubbles stop escaping and a thin mortar film appears on the surface.

What is the correct way to withdraw the vibrator?

It should be withdrawn slowly, at a rate of about 80 mm per second, to allow the hole to close completely without trapping air.

How far apart should vibrator insertions be?

Insertions should be spaced at approximately 1.5 times the radius of action to ensure overlapping zones of compaction.

Can a vibrator be used to move concrete laterally?

No, using a vibrator to move concrete horizontally causes segregation of aggregates and mortar and is strictly prohibited.

IS 3558

: 1983

Method of test for water for concrete

CurrentFrequently UsedCode of PracticeStructural Engineering · Testing Methods and Quality Control

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This code provides comprehensive guidelines on the correct selection and use of immersion (poker) vibrators for consolidating fresh concrete. It details optimal insertion spacing, depth of penetration, withdrawal rate, and essential precautions to prevent segregation and ensure dense, uniform concrete.

Specifies methods for testing water to be used for mixing and curing of concrete.

Quick Reference Values

thickness of concrete layer150 mm to 600 mm

penetration into lower layerAt least 100 mm

time of insertion5 to 15 seconds

rate of withdrawalApproximately 80 mm/s

spacing between insertions1.5 times the radius of action

Practical Notes

Always insert the vibrator vertically to maximize its effectiveness and avoid dragging the reinforcement.

Do not use the vibrator to push or distribute concrete horizontally across the formwork, as this causes segregation.

Ensure the vibrator penetrates about 100 mm into the underlying, still plastic layer to avoid cold joints and ensure a monolithic structure.

Always keep standby vibrators on site during large pours to prevent cold joints in case of equipment failure.