A road well traveled
Tampa, Fla., recently used an asphalt-recycling process to re-pave a major arterial road that carries traffic out of downtown. By recycling the asphalt, the city spent less money and used fewer materials on the project than it would have with a traditional paving process. Additionally, the project was completed quickly, minimizing traffic disruption on the heavily traveled road.
For years, Tampa had maintained its roads using its own paving equipment. In the 1980s, the city was an active proponent of asphalt recycling and owned its own heater-scarifying equipment. The equipment was used to prepare roads for a one-inch overlay by heating existing asphalt to soften it, collecting the top half-inch of asphalt by scraping and lifting it with large tines, and mixing the asphalt with oil before laying it back on the road.
In 1997, the city began working with Safety Harbor, Fla.-based HIP Paving to develop an asphalt recycling system that recovers two inches of the existing roadway and processes it as reconditioned asphalt. The company upgraded the heater-scarifier technology by adding a miller in place of scarifying tines and a standard paving screed instead of a leveling plate. “This moved the process far away from heater scarifying into a full paving mode — and without an overlay. It leaves a finished product as smooth as conventional paving,” says Ken Holton, street maintenance engineer for the city.
By 2002, Tampa’s Cleveland Avenue needed to be re-paved after 18 years of summer heat and heavy traffic. The city considered completing the job with the asphalt recycling process. Cleveland Avenue had been overlaid several times with fresh asphalt, so city engineers knew there were at least two inches of asphalt surface that could be recycled. The four-lane road also had on- and off-ramps to a highway that needed to be kept open for traffic — which would have been difficult with a traditional paving process.
In March 2002, Tampa contracted with HIP Paving to resurface 38,000 square yards of Cleveland Avenue using the hot-in-place recycling process. “The process minimizes the impact on traffic,” Holton says. “The work is isolated to one lane, so traffic can flow past it freely, and as soon as the equipment passes, we have a driving surface.”
The process consists of heating, milling and rejuvenating the top two inches of a road surface and redistributing the recycled material using a conventional paving machine, which puts the finishing touches on the road. The fresh pavement can be driven on within 30 minutes.
By recycling the existing asphalt, the city saved money on disposing old asphalt and using new asphalt materials. “We completed the [Cleveland Avenue] project for $4.25 per square yard vs. the $6.75 it would have cost us with conventional cold mill and overlay paving,” Holton says.
The city expects the re-paved road to last 10 to 15 years. Engineering tests performed last month showed that Cleveland Avenue ranks a 99 on the ASTM Standard Pavement Condition Index (PCI), which rates pavement on a scale of 0 to 100. Holton says that he would have expected a measurement in the 90s for a year-old surface. “It is performing as well as a conventional-type paving process,” he says. “For less money, so far, I’ve seen basically the same results.”