Equipment Type

Vibrating Beam Rubblizes Pavement Fast

Resonant Machines has been operating since 1984 as a subcontractor, using its own resonant-beam technology to reduce concrete pavement to rubble on highway and airport jobs in 36 states, China, Russia, Canada and Chile. A private-equity firm purchased the subcontractor/equipment manufacturer last June and made Eaton veteran Tom Schneider president and CEO.

June 01, 2008

The shoe attached to the front of the steel beam vibrates at just ½ to ¾ of an inch in amplitude, so only the concrete is broken.

A Caterpillar C15 diesel engine drives Sauer pumps through a Rexroth motor and Parker oscillators that vibrate the RB550's 8,000-pound horizontal steel beam at up to 55 hertz.

Resonant Machines has been operating since 1984 as a subcontractor, using its own resonant-beam technology to reduce concrete pavement to rubble on highway and airport jobs in 36 states, China, Russia, Canada and Chile. A private-equity firm purchased the subcontractor/equipment manufacturer last June and made Eaton veteran Tom Schneider president and CEO.

Schneider recruited his resources from the hydraulics industry to rework the Resonant Machines hydraulic system, and now the company is renewing its efforts to market the machines.

The Asphalt Institute defines rubblization as "The process of fracturing Portland cement concrete pavement into small pieces. The sizes will be from sand size on top to 9 inches on the bottom portion of the slab. Steel or wire mesh shall be debonded from all pieces of the broken pavement. Fractured pieces shall have an angular interlock"

RMI says its Resonant Machine breaks concrete up to 26 inches thick to suit the Asphalt Institute definition — and many states' specifications — at a rate of about one lane mile (7,000 square yards) per day. The machine moves briskly, at 5 to 8 miles per hour, making as many as 18 passes to properly rubblize some pavements. Each pass is just a foot wide.

A 500-horsepower Cat C15 diesel drives a series of Sauer Danfoss 250 and 180 pumps through a Rexroth bent-axis motor and Parker oscillators that vibrate the RB550's 8,000-pound steel beam at a variable frequency. The operator can tune the frequency to suit the concrete to be broken.

A shoe fixed to the horizontal beam vibrates along the pavement surface. The hydraulic system agitates the beam at up to 55 hertz. Schneider says the RMI shoe breaks the slab at a 45-degree angle to the surface. The slab is fractured through, debonding concrete from reinforcing steel. Since the shoe is vibrating at just ½ to ¾ of an inch in amplitude, only the concrete is broken.

Large drop hammers can compact the road base and drive broken concrete down into it. In the same way, drop hammers can damage utilities under the pavement.

RMI says resonant rubblizing shatters the slab in a jigsaw pattern, without displacing the interlocking pieces. Schneider claims the resulting material — typically in the 3- to 6-inch pieces specified by major resonant-rubblizing users at the Louisiana and Arkansas departments of transportation — can be compacted and overlain with little risk of reflective cracking. He says the rubblized roadway can be overlain with concrete or hot mix. RMI experience suggests that overlaying rubblized pavement costs about half that of removing and replacing concrete

If specifications call for removal of the pavement, rubblized concrete debonded from the reinforcing steel is easier to load into trucks with an excavator than large chunks. Each truck can haul significantly more rubblized material than slabs because of the increased fill factor.

The 60,000-pound RB550 retails for about $880,000.

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