Without maintenance, asphalt pavement shows rapid deterioration at about the 10-year mark. With maintenance, the same road could remain in good condition for as long as 25 years. As public works entities face increasing demand for infrastructure maintenance and decreasing budgets to fund the work, they need to find strategies for stretching the dollars. But where?

Historically, most asphalt maintenance occurs on a case-by-case, season-by-season basis, with highway managers struggling to keep up with each new maintenance problem as it breaks the surface. But managing roadway conditions on a case-by-case basis can not only be frustrating, it often is counterproductive and wasteful.

By approaching the roadway as part of a system, roads and incorporated infrastructure can be maintained in optimal condition, and budget restraints can be significantly eased.

Look beneath the road
Infrastructure Assessment and Management (IAM) is a comprehensive approach to maintenance that includes roadways, the utilities beneath them, and other incorporated infrastructure. If a roadway needs improvements, the odds are good that the underground utilities (such as storm drains, culverts, water lines, and sanitary sewers) also need to be repaired or upgraded.

Roadways can't be separated from their surroundings. Problems with subsurface utilities are often responsible for roadway deficiencies such as cracking, subgrade failures, and sink holes. An excellent opportunity to upgrade utility facilities occurs when an overlying pavement is being replaced or repaired.

Also, the IAM strategy can be extended to assess future infrastructure needs. For example, many U.S. cities are going green by incorporating walkways, bicycle paths, and other human-scaled infrastructure into their general plans.

Lifecycle management
By incorporating the principals of a pavement life-cycle management (PLCM) program into IAM, public works owners can develop deterioration curves that target critical milestones in the infrastructure life-cycles, and they can assess overall maintenance needs and select optimal times for repairs.

The key to an IAM (ILCM) program's effectiveness is a detailed and comprehensive assessment of infrastructure conditions. This not only calls up a set of appropriate maintenance strategies, but it also activates a sequence of decision-support considerations, including treatment selection, performance forecasting, life-cycle cost analysis, and long-range prioritization. The outcome of this process is targeted information that managers can use for decisions regarding specific projects, budget expectations, long-term planning, and funding requests.

An essential factor in making a comprehensive management system work is expert inspection resources. Here's an opportunity to take advantage of the wealth of technology we have available, including 3-D laser scanning, digital photography, and GPS, which are all used in the data-collection process. Sophisticated GIS technology can enhance utility and infrastructure inventories, condition assessments, and maintenance/replacement schedules.

How it's done
Once all the data are collected, a series of ratings is produced which takes historical data already entered, and information about surrounding conditions into account. These last two items are especially important.

In infrastructure maintenance, past performance can be one of the most critical factors in assessment and forecasting, especially when it contains a long-term history of response to various environmental and use conditions that are specific to a local region. The deeper the reserve of past-performance records, the more likely that forecasts will predict performance with extreme accuracy.

At the same time, assessments and a related ratings system that reflect local expertise can be powerful influences on planning outcomes. For example, in an area where roadway maintenance problems are related frequently to drainage conditions that either cause or exaggerate various kinds of distress, alligator cracking would most likely be associated with a moisture-related cause.

Maintenance of this hypothetical roadway can be approached in two ways, which might be thought of as "pay now" or "pay later." In this scenario, "pay now" is the IAM approach, which would be to look beneath the pavement, mitigate the drainage issues, and repair the pavement as necessary to maximize its lifecycle under the new conditions (i.e., no drainage problems). The "pay later" approach would be to assign more weight to the drainage problem during the pavement condition assessment, thereby indicating that an extensive rehabilitation is necessary. In the long term, IAM is more sustainable, conservative of resources, and cost effective.

From data to action
Once an infrastructure system has been thoroughly inspected and ratings have been produced based on that collection of data, the ratings are combined with cost estimates to determine the degree of action required. The ratings/cost-estimate process also produces an infrastructure performance forecast, allowing for long-range financial planning and project prioritization. With a comprehensive rating and cost-estimate database available, many subsequent management options become available.

The same data can also provide the basis for the preparation, assignment, and administration of repair contracts, as well as monthly status reports on all work being done.

Pavement management beyond resurfacing
Preservation is much less costly than reconstruction. Besides the traditional approach of patching and resurfacing, there are numerous techniques, ranging from simple to complex, for maintaining a roadway pavement.

Crack sealing, which is fairly simple and inexpensive, will reduce freeze/thaw effects and further cracking. Water is one of the primary culprits responsible for pavement deterioration, and crack sealing prevents or slows the penetration of water. The American Society for Testing and Materials (ASTM) established test standards for polymer-modified sealants, which are generally considered the best performers because they relax during full extension, placing less stress on the sealant's bond with the crack.

Chip sealing, also known as "tar and chip," "seal coat," and a number of other regional appellations, falls under the broad category of bituminous surface treatment (BTS), which generally consists of applying a thin layer of liquid asphalt or emulsion binder and covering it with an aggregate. Chip sealing is a short-term remedy that improves roadway surface and extends roadway life. This method is unpopular in urban areas because of the loose aggregate and rough surface. Proprietary methods of BTS are available that produce a smoother surface. One of these is slurry sealing.

Slurry sealing is both versatile and cost effective. The slurry seal consists of a thin asphalt overlay that fills in small cracks and provides a relatively smooth surface, but can also provide some skid resistance when applied to polished roadway surfaces. Unlike chip sealing, a slurry seal does not produce loose stones, but there is a sandy residue that disappears in time.

Geosynthetics, as defined by the ASTM, constitute "a planar product manufactured from polymeric material used with soil, rock, earth, or other geotechnical engineering related material as an integral part of a man-made project, structure, or system." Geosynthetics used in pavement rehabilitation include geotextiles, geogrids, geomembranes, erosion control blankets and mats, geosynthetic clay liners, geocomposite, drainage materials, and geonets. When used in pavement rehabilitation, geosynthetic layers improve the stiffness and bearing capacity of the asphalt roadway and subgrade, in addition to reducing reflective cracking through asphalt layers. The geotextile layer is combined typically with asphalt sealant, or tack coat to form an inter-layered system, which can also serve as a fluid barrier. If not installed properly, a geosynthetic can contribute to early failure, so it's important to understand the various types and applications.

Base stabilization, used as an alternative to reconstruction, is a technique whereby mixtures of aggregate and cementitious material are blended with water to produce a non-plastic material that can be compacted to form a dense mass. Base stabilization techniques include foaming, which recycles existing asphalt; and cement stabilization, which introduces cement and recycles existing asphalt.

If resources abounded, it might make sense to perform intermittent maintenance activities for the 10-year life-cycle of a pavement and then replace it. This strategy is counterproductive in terms of sustainability and conservation, and it's unnecessary. Using the IAM approach, combined with the tools of PLCM, and the multitude of available pavement maintenance technologies, the life-cycle of a pavement can be extended.

Josh E. Rowan, P.E., PgMP, CCM, is PBS&J's construction management manager in Atlanta. He can be reached at 770-933-0280 or jerowan@pbsj.com.