High RAP Mix Design Works

Additional QC measures for mix designs with high RAP content call for increased testing frequencies of the extraction/gradation test and recovered viscosity. The QC plan for the SR 15A project also included additional tests for determining the maximum specific gravity (Rice Method) of the mix design; and the bulk specific gravity (Gsb) was also regularly monitored as well.

One other measure P & S has taken to ensure a high-quality FRAP mix design is produced at the plant is the modification it made to its Astec Turbo 400 Double Barrel control system. The modification allows better control of the drum speed in order to control aggregate veil. This provides for more efficient heating of RAP without increasing baghouse temperatures.

Whenever mix adjustments are required during production, using the fractionated RAP allows the percentage of RAP content to be maintained by simply adjusting the ratio of the two FRAP components (fine and coarse), rather than decreasing the overall RAP and increasing the virgin material, which is the only way to make adjustments when using non-fractionated RAP.

A winning solution

P & S has always taken a progressive approach in identifying and implementing ways to grow its business while maintaining a competitive edge in the market. It didn't take long for the company to rapidly grow its road construction business from a single dozer operation in 1993 to the $60 million company it is today. Expansion into asphalt production, asphalt paving and asphalt milling have all contributed to the methodical approach brothers Tim and Todd Phillips have taken in a commitment to make the company what is today.

So it comes as no surprise that the Phillips have also taken a progressive approach in investing in state-of-the art equipment to expand their production and competitive capabilities, while generating a profitable return at the same time.

P & S purchased a used batch plant in 1998 to expand it construction services into the production and placement of hot mix asphalt. The Phillips soon recognized the potential of the HMA market within the 60-mile radius of their Daytona Beach production facility and decided to replace the aging plant with a state-of-the-art Astec Turbo 400 Double Barrel drum-mixer plant in 2001.

When the plant was fired up in January 2002, the Phillips soon realized they were in the asphalt business and the annual production rates quickly grew. At the same time, increased usage of RAP on FDOT projects also piqued the Phillips' interest, especially with the growing piles of road millings that were beginning to take over their production area.

"We've used RAP ever since we bought the batch plant, but it was on a very limited basis," says Pat Richards, paving operations manager who's been with company from the start. "Before we began fractionating RAP (somewhere around 2002), we were able to incorporate 30 to 35 percent in some of the mixes we were producing.

"Now with our RAP system, we can produce FDOT designs with as much as 50 percent RAP and some other designs for road base work with up to 60 percent," he continues. "What the fractionating system does for us is it gives us the exact same product that we would pull from our virgin aggregate piles, except that the RAP product has a coating of asphalt."

For the SR 15A project, the requirements are the same as with any other FDOT project that's built with RAP mixes or not. Standard FDOT density requirement and smoothness specifications had to be met.

"Even though every mix you produce might be a little different and the conditions during placement may call for different rolling patterns to achieve density and ride quality, the high RAP mixes still perform as well as virgin mix designs," Richards says. "We know the designs work and FDOT knows they work. The entire 15A project is a warranty project, so we're pretty confident of the long-term performance of the job."

Sixty percent of the mix P & S produces and places today is for FDOT, so the relationship the asphalt producer/contractor has built with the road agency is a strong testament of the mutual respect that exists.

"Using a high percentage of RAP in mix designs allows us to control our costs and be more competitive in the bid process. At the same time, we've proven that those designs perform up to FDOT's requirements and we have the quality control measures in place to verify the quality of the mixes we're producing and placing," Richards says.