California Route 33
Reconstruction Near Ojai Good Fit For Cold Foam Asphalt Full-Depth Reclamation

For ten days from late April to mid-May, crews from Pavement Recycling Systems (PRS) were performing a full-depth reclamation project on approximately nine miles of California Route 33 from Lockwood Valley Road to the Santa Barbara County line. PRS performed the project for CalTrans using the foamed asphalt process.

Foamed asphalt is created when small amounts of water come in contact with hot asphalt, increasing the surface area of the asphalt and decreasing its viscosity. Each tiny foam bubble carries a thin film of asphalt, which adheres to the finer gradings of the recycled material, producing an asphalt-enhanced filler that acts as a mortar to bind the larger gradings together. Once compacted, the foamed asphalt stabilized material will exhibit increased strength and durability.

According to the PRS website, “foam asphalt stabilized material can be placed, shaped, compacted and open to traffic immediately after mixing and remains workable for extended periods of time. Stockpiling and delayed placement is possible requiring only moisture conditioning to aid in compaction.”

Full-depth reclamation with foamed asphalt was chosen for this particular project for several reasons, according to Joe Peterson, Materials Engineer for CalTrans North Region.

“This project was a really good candidate for this process because of it’s deteriorated state and limited options if conventional overlay strategies were utilized. It’s also a hilly, windy road with a lot of blind curves,” Joe explains. “Because the crew is basically running equipment and not on the road, they are more protected and it’s safer for all parties involved.

“Safety is always our primary concern, both for the workers and the motorists,” he adds. Another reason the foamed asphalt process made sense for this project is that it allows traffic to be maintained in one lane throughout the reconstruction. California Route 33 near Ojai is the route for many farm and gravel trucks and traffic didn’t have to be rerouted during reconstruction. The site’s geography meant there was limited access, which made the location ideal for this process, Marco Estrada, Division Manager for PRS, says. Because 100% of the old asphalt and base materials are recycled into the new road, there’s no need to export old material for disposal and import aggregate on this type of job.

(Below Left) A CAT CP 563C was used to  perform the initial compaction.(Below Middle) A Sakai GW750 performs finish rolling at the Route 33 project.(Below Right) A CAT motor grader fine grading at the Route 33 project in Ojai, CA.

This type of reconstruction process saves time and money, Marco says. Without the import and export of materials to and from the site, the reconstruction of the roadway usually only takes a matter or weeks, as opposed to months in a typical hot mix asphalt reconstruction.

The foamed asphalt reclamation process begins with pulverizing the existing pavement section. Portland cement kiln dust is added to the recycled materials at a 2% rate to serve as a mineral filler and pozzolan. Hot asphalt is then added at a rate of 2.8 % for a depth of eight inches during the foaming process. A thin asphalt overlay is constructed over the foamed asphalt section.

PRS’ scope of work consisted of pulverization of the existing pavement section, as well as the foamed asphalt stabilization.  Excluding the oil used in the foaming process, PRS’s contract was in excess of a half million dollars.  The general contractor of the project was Granite Construction.  Approximately 1,350 metric tons of oil for foamed asphalt and 830 metric tones of cement kiln dust were utilized on this project.

Pavement Recycling Systems’ CAT 350 Road Reclaimer foam stabilizing the pavement section.

Rick Alvarez, PRS’ superintendent, was responsible for managing PRS’ operations on this project. PRS’ crew of 13 included operators and drivers for two pulverizer machines, two foam stabilization machines, one cement kiln dust truck and four oil trucks. The process was completed with a CAT RM-350B and CMI Terex RS650, both equipped with foam stabilization systems, which are market available pieces of equipment. The CAT RM-350B Reclaimer/Mixer is designed and manufactured for tough full depth reclamation applications. The CMI Terex ROTO-MIXER RS-650B is a high performance, bi-directional Reclaimer/Stabilizer used for a wide variety of base preparation and base and surface reclamation projects. PRS completes full-depth reclamation with foamed asphalt projects throughout the states of California and Nevada. This particular project is a typical size for PRS, although they also complete this type of project for both local governments and the private sector.

Marco says the appeal of foamed asphalt rests on three fundamantal factors: First, the existing roadway was built with fine quality aggregates and binders.  While, over time, the roadway binder has deteriorated - the aggregates are still in excellent condition.  Replacing those aggregates is costly and time consuming. Foamed asphalt is one solution that retains - "recycles" - the existing aggregate.

Second, recycling the roadway in place is faster and less disruptive than removing and replacing the full structural section - so the impact on the road users is less. Finally, the only material imported to the project is the new asphalt used in the foam process.  So trucking impacts on the road and on traffic to and from the project are minimized. These three factors combine to provide a rehabilitated section that is at least as strong as the original design section at a much reduced cost in dollars, resources, and user traffic delays.

	(Top) An oil distribution truck applies oil for foam stabilization to the CAT 350. (Middle) The completed foam stabilize section of Route 33 with temporary striping. (Bottom) A CAT dual vibratory steel drum roller performs the finish rolling on the foam stabilized section.

“For every truck of oil we use on a full-depth reclamation project, we would have had 60 trucks for a traditional “export and import” reconstruction project,” he continues. “The cost savings is tremendous.”

Recycling isn’t the right process for every road reclamation project, though, Joe says. Limited sub-base clay and well-drained pavements are the best candidates, he adds.

“A lot of California’s state highways were once cattle and wagon trails and the base material might not be that stable,” he explains. “Some of the states’ roadways are actually built on clay and silt, without benefit of engineered base material.”

“If we were to use recycling on those roads, the clay and silt would act like Play Doh and cause the recycled material and overlaying asphalt concrete surface to crack,” he says.

CalTrans evaluates roads on a case-by-case basis to determine which reconstruction process is best.

“We started using the full-depth reclamation process about five years ago and it’s been a real success,” Joe says. “We are slowly rolling the process out to the rest of the state. Because we can rebuild 1.5 lane miles a day with this process, it’s an economical way to rebuild the roads in place,” he adds. “We believe this process provides 1.5 to 2 times the life of what a road that’s rebuilt through the conventional process yields.”

According to the Portland Cement Association, the full-depth reclamation process costs 25% to 50% less than the removal and replacement of the old pavement through conventional means.

Contact PRS at (800) 966-7774 or look on the web at www.pavementrecycling.co