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Chapter 5
Pavement, Materials, and Recycling

Despite the increase in public infrastructure investments, pavements and other elements are decaying faster than they can be renewed, in many cases. Factors have included insufficient funds, population growth and increasing infrastructure demands per capita as lower density development spreads out into new areas, tighter health and environmental requirements, poor quality control having led to inferior installation, inadequate inspection and maintenance, and lack of consistency and uniformity in design, and construction and operation practices. The increased burden on infrastructure can hasten and aging process and increase the social, fiscal, and environmental costs with needed repairs.

Increasingly state DOTs are employing pavement management systems to ensure that resources are targeted where they will produce the greatest effect - conservation of existing resources and infrastructure - in the most efficient or cost-effective manner. This enables transportation dollars to go further, and can lead to prolonged infrastructure life and greater periods of time between more environmentally intrusive reconstruction projects.

Environmental stewardship is also practiced in the course of recycling pavement and DOT waste products, and using other recycled materials in DOT pavements and roadside structures. Recycling directly addresses energy conservation needs in construction and maintenance as well.

 

5.1. Preventative Maintenance and Pavement Management Sysytems

Timing is critical in preventive maintenance, as "preventive maintenance is a program strategy intended to arrest light deterioration, retard progressive failures, and reduce the need for corrective maintenance and service activities." [N] Preventive strategies for flexible pavements include seal coats such as chip seals, slurry seals, micro surfacing, thin overlays, and crack sealing. Rubberized asphalt concrete (RAC) usage can extend pavement life and help to address waste and landfill issues while providing a smoother ride, better resistance to cracking than other types of pavement surfaces, and less frequent maintenance. In addition, RAC has the potential to reduce noise levels to a point where a soundwall may not be needed in some locations. Preventative maintenance (PM) treatments for concrete pavements include crack and joint sealing, dowel bar retrofit, partial depth slab repairs, and diamond grinding for smoothness and improved pavement texture. All of these treatments reduce the amount of water that may infiltrate the pavement, slow the rate of deterioration, or correct surface roughness. Timely application can maintain or extend a pavements service life five to ten years or longer before significant maintenance effort is required. Surface treatments also help prevent raveling and improve surface friction properties, but can accelerate vapor action and stripping when applied to aged and open pavements. [N]

Caltrans determined that for every $1 spent on Preventative Maintenance or Capital Preventative Maintenance (CAPM), $3 to $20 is saved if the treatment is applied at the right time, before the pavement deteriorates into a major rehabilitation or reconstruction project. In addition, reconstruction in urban areas is more expensive. Instead of the estimated $200,000 per lane mile, the costs may exceed $1 million per lane mile. In contrast, a PM strategy will typically cost $50,000 to $100,000 per lane mile, covering many more miles for the equivalent dollar. A significant savings for PM comes from a reduction in time spent in design and construction. Prior to PM, for example, Caltrans did as much Corrective Major Maintenance as the limited budget allowed until full rehabilitation, or, in the worst-case, reconstruction was needed. Time spent waiting until the pavement can by fully rehabilitated allows time for the pavement condition to deteriorate further. Since PM projects are pavement only, they require less design time and can be delivered faster. During construction, pavement surfaces are renovated, using thinner treatments, which contributes to faster production rates. Also, less construction working days reduces the disruption to the traveling public and less disturbance to roadside environments. [N]

The factors affecting pavement life include a variety of site conditions, including traffic, climate, and paving material. Condition surveys help predict the occurrence of distress (including density of cracking and the average level of crack edge deterioration), select appropriate maintenance, and program such activities before further deterioration occurs. When crack densities are low to moderate, crack sealing is effective; however, as densities progress from moderate to high, surface treatments are more effective. There are three basic techniques for surface treatment of cracked pavements: slurry, chip seals, and thin hot mix overlays. Selection of the best treatment is a function of the existing pavement condition. Results from the Strategic Highway Research Program (SHRP) suggest the following: [N]

  • Slurry seals perform best when applied to pavements with little or no cracking.
  • Chip seals perform well on cracked pavements, but add no structure and do not improve rideability.
  • Thin hot mix overlays perform better than other treatments on pavements with higher roughness and/or rutting. They are also effective as a seal, and they prevent raveling.

The Federation of Canadian Municipalities and the Canadian National Research Council also have developed Guidelines for Sealing and Filling Cracks in Asphalt Concrete Pavement: A Best Practice by the National Guide to Sustainable Municipal Infrastructure. Other publications included in their National Guide are Timely Preventive Maintenance for Municipal Roads, a primer on preventative maintenance methods, setting priorities, and cost analysis; Priority Planning and Budgeting Process for Pavement Maintenance and Rehabilitation, a n eight-step approach to budgeting and timely maintenance; and Alberta Transportation's Guidelines for Assessing Pavement Preservation Strategies.

Pavement management systems have helped DOTs prioritize improvements and document the cost-effectiveness of preventative maintenance. In a shift to a more pro-active road maintenance strategy, Nevada DOT is prioritizing projects based on how quickly roads are deteriorating or prediction models, not on the basis of their current condition. Prevention strategies are ranked by life-cycle cost, not initial cost. NDOT deployed cold-in-place recycling based on a sophisticated lifecycle cost comparison; the state optimized its projects by assigning roads to five categories based on volume and environmental conditions. [N] Caltrans is among the state DOTs publishing a State of the Pavement Survey. Pavement condition is evaluated using ride score (IRI) and the pavement surface condition. The PMS provides a systematic, objective evaluation of pavement condition for identification of maintenance and rehabilitation needs and projects, and then prioritization of those projects. The tool can help a DOT track progress toward reducing total pavement needs to specified target levels as well as in improving pavement conditions overall.

 

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Table of Contents
 
Chapter 5
Pavement, Materials, and Recycling
5.1 Preventative Maintenance and Pavement Management Systems
5.2 Stormwater Management in Paving Operations, Grinding, and Pavement Maintenance
5.3 Flexible Pavement/Asphalt
5.4 Concrete Installation and Repair
5.5 Pavement Marking
5.6 Curb and Sidewalk Repair
5.7 Recycling in Pavement and Roadside Appurtenances
5.8 Maintenance of Dirt and Gravel Roads
   
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