Concrete Vibrator

Overview

A concrete vibrator consolidates freshly placed concrete by immersing a high-frequency vibrating head into the wet mix. The vibration fluidises the concrete for a few seconds, letting trapped air rise out and the paste flow around reinforcing bars and into the corners of the formwork. Without this step poured concrete sets with voids and honeycombing that weaken the structure and spoil the surface finish.

This unit is an electric immersion type, also called a poker vibrator. A hand-carried power unit built around the Drive Motor spins a Flexible Shaft Assembly that runs out to the Poker Head, the steel tube the operator dips into the pour. The operator holds the unit by the Handle Assembly and controls it with a sealed On/Off Switch, with power fed through a heavy-duty Power Cord Assembly. A 1,500 W universal motor drives a 38 mm head at roughly 12,000 vibrations per minute over a 4 m shaft.

How it works

The universal motor turns at high speed and couples through the flexible shaft's inner core to the head. Inside the Poker Head the core spins an eccentric pendulum mass on its bearings. Because the mass is offset from the axis, its rotation throws the head tube in a small circular orbit thousands of times a second. That orbit, about 1.8 mm of amplitude at 200 Hz, is the vibration transmitted into the surrounding concrete, generating around 4.5 kN of centrifugal force at the head.

The head is sealed against the slurry by its bearings and exclusion seals so the eccentric runs in a clean cavity while the outside is buried in abrasive wet concrete. The flexible shaft lets the operator reach down into deep lifts and around congested rebar while keeping the motor and the operator's hands clear of the pour. In use the head is plunged vertically about every 450 mm, held until the surface glistens and large bubbles stop rising, then withdrawn slowly so the hole it leaves closes behind it.