City of LA Finds path to better concrete paving
Los Angeles- When paving a new 4,000 foot concrete bike and pedestrian path, the City of Los Angeles reduced both time and costs by using reusable metal concrete forms that were easy to set and a truss screed that simplified finishing.
The city recently completed the path, which links an existing bike path in Burbank to the NOHO (North Hollywood) arts district. It is 16 feet wide by six inches thick, laid on top of a 98 percent compacted four-inch thick crushed aggregate base (CAB). A 6-6-10-10 wire mesh reinforcement was pulled up halfway through the thickness of the concrete with hooks during the paving process.
Metal Concrete Forms Provide Superior Cost-Efficiency
Instead of wood forms, which can be used a limited number of times and are difficult to clean, the city chose Base Line™ heavy duty forms from Metal Forms Corporation, of Milwaukee, Wisconsin. These 10 gauge steel concrete forms are easy to set up and are designed to provide long service life. They incorporate box-type stake pockets with wedges, which eliminate nailing and allow quick vertical positioning of the forms without the need to pull nails. They also feature full-height end connections that make it easy to connect the 10-foot form sections and provide full depth alignment, with a sturdy, reinforced joint.
A vibrating truss screed from Metal Forms Corporation was used to strike-off, consolidate and finish the concrete. It included a 5-1/2 foot power section with 10 and 2-1/2 foot extensions, plus a hydraulic winch and a back-up hand winch. It also incorporates square finishing tubes that are reversible to extend the life of this part, which commonly is subject to the most wear. Ready-mix concrete with a four-inch maximum slump was used. Street Services Supervisor Patrick Singleton says, “We wanted to keep the moisture content really low on this job to prevent cracking, and we let the screed do the rest of the work.
A construction joint was placed every 10 feet and an expansion joint every 200 feet. The path also is divided into lanes, with 11 feet of width for bicycles and five feet for pedestrians. A sawcut joint delineates the separation, and for further delineates, the finish is broomed longitudinally for the pedestrian portion but transversely for bicycles. At both ends of the path, as well as at two intersections along its length, sections were colored to form a decorative end cap. The path’s six-inch thickness makes it suitable for supporting emergency vehicles and motor sweepers that may be driven over it on occasion.
Concrete Paving Forms - Continued Use
Although no comparative cost figures are available, Construction Estimator Glenn Hoke figures that the city saved enough by using the Metal Forms products on this job to purchase the company’s Poly Meta Forms® for use on other jobs. These reusable polyethylene concrete forms are strong, yet lighter to handle than wood, easier to stake accurately, and available for use on straight or radius applications.View All Field Reports