Recycle the Process
BY Jarrett Welch
The American Road and Transportation Builders of America (ARTBA) estimates there are 4.09 million miles of total roadways in the United States, and according to the National Asphalt Pavement Association 2.6 million miles are paved roads or highways, with 93 percent—or 2.4 million miles—surfaced with asphalt. ARTBA also estimates local governments are responsible for maintaining and preserving 77.5 percent of the total miles of roadway in the country. When city and county planning boards find themselves short on funding, they need cost-effective methods to maintain their infrastructures. Specifically, the people responsible for maintaining rural area roads seek creative solutions to determine what is the best bang for their buck. Have we as an industry shared with these officials what is available to them?
We have used sustainable technologies and processes for many years. Over time we have improved on these methods to increase efficiency, reduce costs and provide a higher quality pavement.
In the past decade we have made advancements in our recycling efforts that provide government entities additional opportunities for maintaining their roads. There are a number of roadway rehabilitation methods in the tool box, but two that are gaining momentum for their use on rural roadways are cold in-place recycling (CIR) and cold central-plant recycling (CCPR). (Editor’s
Note: See the October 2014 issue’s “Unveil CIR Mysteries” for a technical discussion of how to perform CIR while avoiding some of its pitfalls; and the January 2015 issue’s “Recycle with a Plant In-Place” for our most recent in-depth look at CCPR.)
In a nutshell, cold in-place recycling (CIR), is a process that rehabilitates a roadway to a depth between 2.5 and 5 inches by cold milling and mixing the mill tailings with asphalt stabilizing agents. Once mixed, the material is either picked up and placed with a conventional paving machine or blade-graded and compacted to a specified density. Cold central-plant recycling (CCPR) is a similar process; however, the millings are completely removed from the roadway and transported to a central plant location. There they are processed for gradation and mixed with the asphalt stabilizing agents to be then hauled back to the project for placement and compaction.
Both processes rehabilitate a pavement to repair basic distresses, but are not intended to correct structural deficiencies. Commonly, these processes are used to rehabilitate pavements that are structurally sound but have succumbed to an aged and oxidized binder that have developed block, longitudinal or transverse thermal cracking. Other distresses such as raveling, rutting and irregular profiles can also be corrected with these methods.
These are just two examples of processes that haven’t changed very much over the years, but the continued improvement of the emulsions used as the asphalt stabilizing agent has helped keep them a viable option in maintaining and preserving roadways.
One approach that has improved is the chemical engineering of our emulsions and binders that allows for higher percentages of binder in the reclaimed asphalt pavement (RAP) to be better used. Shane McDade, president of Road Recyclers is one individual who has worked extensively to develop emulsions that provide better performance while at the same time keeping the material from being cost prohibitive.
“The goal of Road Recyclers is to offer value to agencies and the taxpayers they serve,” McDade said. “Producing a good product that costs too much is not adding value. Neither is producing cheap products that don’t perform. This is why we commit so many resources to engineering before projects and QC during projects.”
McDade has developed emulsions that contain components with rejuvenation properties that are designed to allow the binder in the RAP material to be reactivated. By doing so, he then reduces the amount of virgin binder included in the blend, allowing for more miles of roadway to be rehabilitated or as a cost savings to the agency.
Jon Heese, maintenance project coordinator for Arapahoe County, Colo., hopes for those results. At press time, Heese was putting together a CIR project to address distresses along a 5-mile section of the Kiowa-Bennett Road. The roadway connects the Town of Bennett, located along Interstate 70 at the north to the Town of Kiowa 30 miles to the south. Over the years, this particular roadway has developed rutting due to the heavy truck traffic and farming equipment it carries, and transverse thermal cracking. Due to his budget constraints, Heese has looked at several options to address this roadway and believes the CIR process using Texas Road Recyclers’ ProRAP emulsion will cost the county approximately half as much as other methods considered.
This is good news for the county, as they would not be able to bid the project using higher cost alternatives. In times of economic adversity, ingenuity is born. This forward thinking benefits everyone, but most importantly it benefits the tax payers who use the roads we build.
Jarrett Welch is the proprietor of Quality Paving Consultants, Wheat Ridge, Colo. For more information, contact him at (970) 361-1525.