With the Alaska Department of Transportation and Public Facilities’ growing interest in Transportation Asset Management, the department is gathering the administrative tools to implement a statewide pavement preservation program. Supporting this effort, an Alaska University Transportation Center study recently produced a draft Pavement Preservation Guide for Alaska. In it, researchers evaluate cold-region preservation techniques and give decision makers guidelines and matrixes to choose the most attractive treatments for Alaska.
Alaska spends up to $140 million a year on surface maintenance. Studies show that active pavement preservation programs save more than 50% in costs over a pavement system’s 20-year life cycle. These figures suggest a fully implemented pavement preservation system could save ADOT&PF as much as $350 Million in a five-year period.
Before implementing such a system, ADOT&PF needs better information. Although experienced with numerous pavement preservation treatments, the state has yet to fully implement a comprehensive system. Many unknowns remain.
What pavement treatments are available? Which are most attractive from a cost perspective? Which ones best maximize pavement life-cycle? What are other cold regions doing? What treatments is ADOT&PF already using?
Answering these questions, a study called “Developing Guidelines for Pavement Preservation Treatments and for Building a Pavement Program for Alaska,” surveyed technical literature, cold region transportation experts, and numerous site locations to recommend treatments for Alaska. Led by AUTC’s Jenny Liu and Gary Hicks of the California Pavement Preservation Center (CPPC), the project completed a draft Pavement Preservation Guide in January that lays out their findings. They also created a database of Alaska-specific projects available online here.
The Guide identifies 11 commonly-used pavement treatments for use in Alaska’s management system. These include: crack sealing, patching, fog seals, chip seals, slurry seals, AST/BST, microsurfacing, thin overlays, bonded wearing courses, interlayers, and in-place recycling. Their average service life ranges between 3 and 12 years. The guide also supports continuing two techniques currently used in Alaska—crack sealing and patching. In addition, it suggests the state research and evaluate the effectiveness of slurry surfacing and pre-saw cut joints—techniques used in other cold regions. It also specifies which techniques perform well in terms of costs and life-cycle enhancement.
When it comes to cost-effectiveness, crack sealing was the least costly of these at $.75 to $1.50 per foot. Slurry sealing ($.75 to $1.00/yd²) was the second least costly method, and single-course microsurfacing ($1.50 to $3.00/yd²) tied with conventional single-course chip seal ($1.50 to $2.00/yd²) for third. Conversely, the techniques that most significantly enhance service-life are microsurfacing and thin overlays.
So, what is the most attractive treatment for Alaska? Generally speaking, the Guide shows that Microsurfacing is commonly used in cold regions, has a long service life, and is inexpensive. The study also notes that HMA overlays, various chip seals, and crack sealing are the most widely used treatments in Alaska to date. However, while the study stops short of endorsing one or two ‘best practices,’ it offers an entire preservation strategy selection guide for ADOT&PF.
It stresses that multiple factors influence pavement treatment selection: pavement age, condition, traffic levels, expected future plans, available funding, and agency policy. The selection guide also includes matrixes for evaluating both crack and non-crack related preservation strategies. While they depend upon an existing level of pavement condition evaluation, these matrixes include numerous variables, assessment levels, and treatment categories.
While the draft Pavement Preservation Guide undergoes internal review, Liu and ADOT&PF counterparts will soon begin a series of workshops starting with the Alaska Asphalt Pavement Alliance’s upcoming meeting, and another using a Go To Meeting. They will convey many of the guide’s take-away lessons to the professionals who deal with pavement preservation issues every day across Alaska.
This story originally appeared in AUTC’s Quarterly Newsletter (Volume 5, Number 2). Read it and other stories on AUTC’s work online here.