Good consolidation makes good concrete. How you get it is another thing.

Precasters have used external vibrators to achieve good consolidation for years, but cast-in-place contractors have most often relied on internal vibration. Flexible shaft vibrators have done yeoman's work at the jobsite, but they need an operator's skill and experience to consistently achieve good consolidation. Internal vibrators also can face difficulties with complicated shapes or areas of rebar congestion.

External vibrators can produce good surface finishes, but traditionally they have been heavy, bulky, and difficult to attach to the formwork. Wacker Corp. has spent three years working with European formwork manufacturers redesigning the external vibrator to address these and other problems. Its answer is the new plug-and-play system, an electrical system that uses an AR36 42-V vibrator to produce up to 6000 vibrations per minute. The system's major advantage is that it allows users to dial in the amount of energy for almost any specific application, providing complete consolidation while avoiding blowouts and segregation.

Another advantage is that these vibrators can be operated and the frequency can be adjusted manually or with radio remote control. This can help reduce labor costs by reducing the number of workers using internal vibrators, which enhances safety by removing the need for people climbing atop the formwork.

The motor uses a unique inverter to transform 220-V, single-phase into 42-V, 3-phase, a safer power supply, says Bob Becher, Wacker's business development manager for its concrete solutions/precast division. The inverter can work with as many as six vibrators at a time.

The new vibrators (with clamps) weigh as little as 20 pounds, and the specially designed vice clamps fit most steel and plywood formwork systems, including Symons, Doka, Hunnebeck, Peri, Meva, and Paschal. They attach in seconds. For walls up to 12 inches thick, placing vibrators on one side of the form is sufficient.

Many companies offer concrete vibrators, both internal and external. You can find a more complete listing of vibrator manufacturers at

To learn more about Wacker's new external vibrators, call 800-770-0957, visit, or circle 8 on the reader service card.

Handheld vibrator delivers portable power

The EZ Vibe is a versatile, gas-powered concrete vibrator designed to deliver portable power to hard-to-reach areas. It uses a 1 3/8-inch Wyco square head on a 6-foot shaft and a 1.6-hp, 4-cycle Robin engine. This lightweight tool is perfectly balanced and includes a shoulder harness. It is well suited for footings, 4-inch retaining walls, flatwork, box culverts, road patching, and tilt-up walls. The Wyco Tool Co., 800-233-9926, Circle 9.

Two powerful backpack concrete vibrators

Oztec backpack vibrators allow operators incredible maneuverability around the job. Using rugged and dependable Honda engines and coupled to a “speed up” transmission, the vibrator heads develop 12,000 vibrations per minute (vpm). They never drop below 10,500 vpm, even in low slump concrete. Mounted on comfortable frames, the BP-31 runs up to 1.5-inch vibrator heads; the BP-50 fits up to 2.5-inch vibrator heads. Oztec Industries, 800-533-9055, Circle 10.