It’s not easy repairing and repaving roads in heavily traveled areas. In August 2010, the City of Beverly Hills had 1.3 million sq. ft. of roads that needed repaving, a tough job for any contractor. The city not only needed the job done but it wanted to reduce congestion due to construction as well. Sully Miller Contracting and Pavement Recycling Systems, Mira Loma, CA, was brought on board to do the job.
The solution was to use a process called cold in-place asphalt recycling (CIR). In this process, the existing pavement is milled, recycled, and used in the new pavement all right on the job. “Cold in-place asphalt recycling is a way to take the existing asphalt and reuse it on site at a substantially reduced price of traditional mill and fill,” says James Emerson of Pavement Recycling Systems. The recycled asphalt is used as the base course for the new asphalt being placed.
CIR is done using a train of asphalt milling, recycling, and paving equipment so the logistics of situating the train on the busy roadways had to be planned out, says Marco Estrada, P.E. Pavement Restructuring Division of Pavement Recycling Systems. Plus, motorist access had to be maintained. Estrada says the city required that one lane of traffic be open in both directions at all times. The roads were between 50 and 60 feet wide so Sully Miller would open the outside lanes to traffic while working on the inside lanes and vice versa.
The two companies had a crew of 20 employees working on the job for the milling, recycling, and paving. The entire process only took eight days, Estrada says.
The CIR Train & Process
The first piece in the train was Pavement Recycling Systems 12½-ft.-wide cold planing milling machine. It milled a 12.5-ft.-wide pattern at 3 in. deep, Emerson says. That front mill towed a 100% closed circuit portable recycle plant behind it. The milled asphalt was crushed and screened in the recycling plant until 1-in. material passes. That material was weighed on the plant’s bridge before it was delivered into a pug mill.
In the pug mill, the material was blended with Western Emulsion’s engineered Pass-R emulsion, Emerson says. The emulsion serves as a binder and rejuvenator for the recycled asphalt, Estrada adds. “The recycled asphalt is old and dry. The emulsion softens the existing asphalt and then binds everything together,” Estrada says. After the emulsion is added, the material is then dropped below the unit where it was picked up by Sully Miller’s material transfer vehicle and added to the hopper of the paving unit, which is the last element of the CIR train. Sully Miller then paved the road as usual.
To make sure the CIR and newly paved road were meeting mix design specs, Pavement Recycling Systems took core samples throughout the project and had a laboratory conduct a mix design, Emerson says.
Before deciding on the CIR process, Emerson says Juan Martinez, Senior Civil Engineer for the City of Beverly Hills, observed two other CIR projects. CIR on this particular project offered the city multiple benefits.
CIR has a small carbon footprint because it does not require trucking new asphalt from a plant to the jobsite. Emerson estimates that they eliminated 2,800 trucks from the roadway on this particular project. The reduction in trucks also meant no waiting around for mix to be delivered. Plus, having both the milling/recycling and the paving crew working on site at the same time meant no one had to wait to do their job. So the project saw a reduction in construction time by one-third, Emerson adds. Emerson says a CIR provides a tighter surface than traditional milled surfaces. There is less loose gravel on the roadways for drivers to encounter. This results in virtually no damage to vehicles. CIR also offers costs savings. Emerson estimates a total of 42% cost savings for the Beverly Hills CIR project.
The City of Beverly Hills was so pleased with the CIR process that Emerson says it is considering using the same process to reconstruct an additional 28 streets. And with the ability to continually recycle asphalt every 20 years, Emerson says CIR means one pavement system no longer has to have only one lifespan.