In recent years, CCPs have been used successfully on several major soil stabilization projects in the Texas Panhandle area, including the following:

Highway 287: CCPs were used for full-depth reclamation on this high-traffic road. Roadwork included 4 inches of recycled asphalt mixed with 6 to 8 inches of sand and gravel base material. Fly ash was added at 10 percent and water was direct injected. The base was compacted in less than 30 minutes after the water was added. Prime oil was added on the base course within 24 hours of finish grading. Finish rolling was modified to facilitate the prime oil penetration. The paving contractor exceeded its projected productivity by 100 percent, processing more than 400 tons of fly ash per day on the project.

Highway 60: An 8-inch subgrade was treated, using 8 percent fly ash. The 12-inch base material was also treated with fly ash, added at a rate of 10 percent. The material was spread with a spreader bar, using direct water injection. The base was compacted in less than 45 minutes.

Highway 33: After initial startup, the subgrade and base courses of this road began to fail. In response, the paving contractor added fly ash to increase performance of the subgrade. The project used direct water injection. The base was compacted within 1 hour.

Highway 15: The paving contractor added fly ash to the subgrade at a rate of 8 percent and a depth of 8 inches. The highway’s base course was also treated with 10 percent fly ash to a depth of 12 inches. Water was directly injected and the base was compacted within 1 hour.

Highway 70: This project included full-depth reclamation of a 2-inch asphalt pavement and 8- to 10-inch sand-and-gravel base course. The project used a 10% fly ash addition. Direct water injection was not used. Compaction time was 2 hours. The exposed base material was wet cured, and a prime oil was applied within 24 hours. A chip seal was then applied. The highway was opened to traffic for more than 30 days, after which a 2-inch layer of hot mix was applied. The project eliminated a recurring problem with potholes.

Every year in the United States, more than 1.5 million tons of CCPs - primarily fly ash - are used in road base projects, according to the American Coal Ash Association. In addition, CCPs deliver significant environmental and economic benefits. The U.S. Environmental Protection Agency promotes their use to reduce greenhouse gases. And they’re inexpensive and widely available.