Seven Miles of Noise Barriers: Small pump places big yardage

Residents and business owners in Miami located close to I-95 should soon see a drop in noise levels as contractors are working toward a mid-summer completion of all-concrete noise-barrier walls on both sides of the highway.

A small concrete line pump is responsible for placing some big yardage on the upper wall sections of the $38-million project.

The project is located between State Route 112 and the Brower County line. It calls for 12,000 feet of wall along the southbound lanes and 27,000 feet next to the northbound lanes – a total of about 7.4 miles and 45,000 cubic yards of concrete.

The walls are aligned only 8 feet from the outside shoulders of the roadway, forcing the shutdown of a shoulder and one lane of traffic to make room for construction equipment. Gilbert Southern Corporation of Atlanta – which holds the prime award – removed existing guardrail and concrete safety barriers. The design calls for a Jersey barrier to be poured in place atop the footing. A rented boom pump makes the footing and the 3-foot-8-inch Jersey barrier pours before the high wall concrete is placed.

The heavy traffic volume resulted in concrete pumping being restricted to overnight hours. “All construction equipment must be off the roadway by 6:30 a.m.,” says Eduardo Ronriguez, senior project engineer for Parsons Brinkerhoff, Inc. of Miami, a consulting engineering firm that is managing the project for the Florida Department of Transportation. “The ready-mix supplier is running up to nine mix trucks, with 10-yard loads, and it would be impossible to build the walls without causing long delays during the daytime.”

From its ready-mix plant at Biscyane Boulevard and 146th Street, Rinker Materials makes 15-minute hauls after the roadway is closed to traffic at 9:30 p.m. Mike Ballard, operations foreman says his firm batches and delivers an average of 180 cubic yards each night.

Actual pumping time is about six hours per night. Rinker is supplying a design with Type II cement, #57 rock, and Ortoma sand for a footing mix that slumps at 3 inches.

With its 55-mph axle, a compact Schwing BPA-500 trailer pump from the company’s Small Line Division is positioned each night at a mere 8 feet from the metal gang forms of the upper walls. After the grade-beam and Jersey barrier pours are made by the boom pump, the BPA-500 pours the high-wall concrete.

Gilbert Southern, which owns the small pump, determined that it could maintain the pace of a relatively high yardage job. The nearly 7 miles of poured barrier wall range in height from 15 to 23 feet.

In a typical night’s work, the contractor is completing 160 feet of wall, making two 80-foot-long pours that consume 175 cubic yards of mix. Concrete volumes combined for the separate pours are 100 yards for footings, 15 yards for Jersey barriers, and 60 yards for upper walls.

During the pumping operation, flexible line from the Schwing 500 extends to a standpipe running up the wall form. Mix is the discharged through elephant-trunk chutes into the form. A 5-foot freefall is allowed, and the pump places pearock mix in 3-foot, vibrated lifts, Rodriguez says the 40-foot wall-section forms are stripped after 50 percent of the 5,500-psi designed strength is achieved. With a 20-gallon fuel tank that allows all-day or all-night pumping, the Schwing BPA-500 also can place standard mix designs, grout, and shotcrete. In high-traffic areas, the pump’s compact size and remote operator control system help provide a secure pumping operation. The BPA-500 will have been responsible for placing approximately 16,000 cubic yards of upper-wall concrete by the time the project is completed in July 2002. With the job 38-percent complete in mid-January, work is progressing at about 1 mile a month of completed wall.