A joint effort led to the inclusion of full-depth reclamation (FDR)* in the FAA’s Standard Specifications for Construction of Airports, also referred to as FAA Advisory Circular 150/5370-10H.
It started from the FDR being promoted to airport owners, most notably by the Southeast Chapter, says Gary Mitchell, ACPA’s VP of Airports and Technology. He says the Chapter and other ACPA promoters have done an outstanding job promoting FAA projects, adding, “they’ve completed several where they’ve rehabilitated pavements with in-place cement-treated base material, but those projects often had to be completed through a modification of existing airport pavement construction standards.”
“A lot of times, promoters would discuss projects with engineers, who expressed interest, but explained they would have to do a modification of standards and often would hear there wasn’t enough time to do so,” Gary says. It’s often difficult to get engineers to push a modification of standards through the FAA because it takes a long time for them to go through the process, he adds.
The process involves the engineer submitting the modification request and reasoning to the FAA district office or ADO. “The ADO can make decisions on some modifications, but for that particular type of modification, they would have to send it up to the region for review, and if they agreed with it, they would have to send it to the engineers at FAA headquarters,” Gary says. If they approved it, he says, the response would then have to follow the same path back to the ADO and then to the engineer.
“In all, the process could take anywhere between a few weeks to as much as three months,” Mitchell says, adding, “It was really a burdensome process and it wasn’t done as often as we would have liked, so the FDR strategy wasn’t considered an alternate on a lot of projects because it was too difficult to get the modification quickly.”
All of this changed during the process when Gary, with support from contractors and other members of ACPA’s Airport Task Force were working together with the FAA on a revision of the FAA’s 150/5370-10 standard. The entire construction guide specifications were revised during the review and revision process, including specifications for concrete pavement construction (P-501), aggregate base course (P- 209), cement-treated base course (P-304), and other specifications.
“We discussed with the FAA the development of the FDR spec so we could avoid going through modifications,” he says. “They were receptive to the idea, which we advocated because it would give engineers the option using a specification instead of the cumbersome modification of standards.”
Gary says during almost daily conversations with key FAA officials, notably Doug Johnson and Greg Cline, were instrumental in identifying potential challenges and working through changes efficiently. Messrs. Johnson and Cline are both Senior Civil Engineers and pavement subject matter experts (SME) for the FAA’s Office of Airports Safety and Standards, Airport Engineering Division in Washington, DC.
On a parallel path, Gary said he was also having discussions with key personnel at PCA, including Wayne Adaska, Director of Pavements & Geotechnical Markets, Dr. Paul Tennis, Director, Product Standards & Technology, and others at PCA who recommended specification language, provided technical guidance, and joined in the discussion. He also credits long-time PCA member Al Innes, who remains active with LafargeHolcim and the MIT Sustainability Hub. Together, this group provided sound engineering judgment and technical information, which led to the FDR specification.
During the months-long process of marking up the FAA’s 5370-10 standard, now known as FAA Advisory Circular 150/5370-10H, Gary says the PCA representatives, Al Innis, and ACPA Airport Task Force provided excellent support and expertise. He adds that members of the ACPA Airport Task Force also participated in the reviews of the specs related to concrete pavement construction. He adds that Martin Holt of Interstate Highway Construction, Angela Folkestad of the Colorado-Wyoming Chapter-ACPA, and Harold Honey of Michael Baker International participated in a comprehensive review and mark-up of the standard.
Gary emphasizes that long-term relationships and open and forthright discussions with Doug Johnson and Greg Cline also helped the revision process go smoothly. Gary is also quick to credit other organizations** that provided input on the standard.
The net result of this team effort is a standard that now includes FDR specification language, which allows engineers to easily and quickly incorporate the FDR strategy into airport rehabilitation plans, while at the same time, streamlining the overall pavement rehabilitation process. The ultimate beneficiaries are the airports, airport owners’ representatives, and of course, the taxpaying public.
* Full-depth reclamation (FDR) is one of several cement-based rehabilitation strategies, which involves recycling an existing asphalt pavement and its underlying layer(s) into a new base layer, according to the National Concrete Pavement Technology Center (CP Tech Center). FDR with cement increase the structural capacity of the new roadway by providing a stronger, more consistent base, the CP Tech Center says.
** Other organizations included: Airports Consultant Council, American Society of Civil Engineers, Asphalt Institute, Geosynthetic Materials Association, and National Stone Sand Gravel Association.
Photo courtesy of Greg Dean, Carolinas Concrete Paving Association.