Arnold Air Force Base, Tenn. -- Arnold Air Force Base has gained a new tool in its paving arsenal. Known as full depth reclamation, or FDR, it is a sustainable pavement rehabilitation technique that involves recycling the full thickness of asphalt pavement and a portion of the underlying materials (base, subbase, and subgrade) to create a new, stabilized base layer.
FDR has recently been implemented in several paving projects on base with positive results according to Arnold AFB Civil Engineer Ryan Regrutto. This implementation of FDR is a game changer in both cost and effectiveness for civil engineers at Arnold, headquarters of Arnold Engineering Development Complex.
According to Regrutto when taking on a project, “due diligence” is exercised to better understand how things were done in the past along with current conditions to best determine how a project will play out.
“CE project managers and project designers do their due diligence to review as-built files in order to understand current site conditions. Despite all the information available sometimes gaps in records exist, and ultimately assumptions are made,” he said.
Recently he was tasked with the paving project of the building 676 parking lot. Regrutto explained that there was no anticipation of a complicated job. However, due to the appearance of what he refers to as “Arnold’s famous silty loam mud,” a problem arose.
“The parking lot was not built on any subgrade structure,” he said. “The conditions we found at the parking lot were essentially just asphalt on dirt. That’s not how it’s normally done. You need to have a subgrade underneath. An unforeseen site condition like this would normally result in project delays as the contractor would be responsible for removing hundreds of cubic yards of existing soil and then replacing that volume with subgrade consistent with today’s building standards.”
Regrutto continued to explain that while the circumstances unearthed at the site were not ideal, immediate action was taken to find a solution.
A solution was quickly put into play thanks to relationships with both Air Force and local contractors. Regrutto stated that these relationships help to create environments where cutting edge innovations can be discussed and ultimately implemented to provide the best value to Arnold and the taxpayers.
“We have very good local contractors on the Paving IDIQ, the contractor who had won that particular contract recommend that there was an opportunity to use this method that would save time and money. Anything we can do to expedite the process and make it cost-effective is certainly what we are looking for,” he added.
Implementing the solution of using FDR, the project was completed successfully according to Regrutto. With the concept of FDR now proven, he added that FDR was utilized as part of the recent Sixth Street repair project.
“A section of the street was showing signs of base course or subgrade failure with rutting and alligator cracking” he said. “FDR is tailor made for these situations as it virtually eliminates excavation, haul off, aggregate placement, and keeps materials out of the landfill. The amount of man hours required to prepare the base course is fractional compared to traditional excavation resulting in a 10 to 20 percent cost savings.”
With this technique saving both time and money, FDR will continue to be utilized in future projects.