Credit: Photo: Metal Forms Corp.
Four-inch steel forms were set on blocks to provide the concrete path's required 6-inch thickness. The reinforcing wire mesh shown here was pulled up into concrete once poured.
When the Los Angeles Bureau of Street Services needed to pour a 4000-foot bike path that connects an existing path in Burbank, Calif., to the North Hollywood arts district, it abandoned traditional wood forms in favor of reusable metal forms and a truss screed that simplified finishing.
In addition to saving the department time and money, the new 16-foot-wide, 6-inch-thick concrete path is strong enough to support the occasional emergency vehicle and sweeper.
Because wood forms can be used only for a limited number of times and are difficult to clean, the city decided to try Base Line heavy-duty forms from Milwaukee-based Metal Forms Corp. The 10-gauge steel forms incorporate box-type stake pockets with wedges, eliminating nailing and allowing quick vertical positioning without the need to pull nails. They also feature full-height end connections that easily connect the 10-foot form sections and provide full-depth alignment with a sturdy, reinforced joint.
Although the bike path is 6 inches thick, the city had purchased 4-inch forms, so workers set them on blocks to support the screed and provide the added height. Typically, the crew set the forms one day and poured the next. Reinforcing wire mesh was pulled up into concrete once poured.
“A crew of 12 worked best, with five people in front of the screed placing the concrete and pulling the wire mesh up; two people running the screed; and five more behind the screed running the bull float, cutting the edges and joints, and doing the final finishing and brooming,” says street services supervisor Dennis Martin Jr.
Ready-mixed concrete with a 4-inch maximum slump was used to keep the moisture content low and prevent cracking, says supervisor Patrick Singleton, “and we let the screed do the rest of the work.” The crew used Metal Forms's Speed Screed Cruiser vibrating truss screed to strike off, consolidate, and finish the concrete.
A construction joint was placed every 10 feet and an expansion joint every 200 feet. A saw-cut joint was used to divide the path into bicyclist and pedestrian lanes. For further definition, the finish was broomed longitudinally for the pedestrian portion and transversely for bicycles. Crew member Roy Ponce developed a longitudinal broom to finish along the path's length without walking on the fresh concrete. At both ends of the path, as well as at two intersections, sections were colored to form a decorative end cap using Los Angeles-based L.M. Scofield Co.'s “Sombrero Buff” coloring.
The path is laid on top of a 98% compacted, 4-inch-thick crushed aggregate base. Although no comparative cost figures are available, construction estimator Glenn Hoke figures the department saved enough money to buy forms for other jobs.
— Tom Miller is president of Metal Forms Corp.