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Publication Number: FHWA-HRT-11-065
Date: April 2012
This chapter considers research-related needs related to monitoring and improving long-term concrete pavement performance and maximizing economic value throughout a pavement’s life cycle.
In the past, pavement performance requirements have focused on serviceability (i.e., ride quality) and friction. Now, performance indicators, such as tire-pavement noise, splash and spray, potential for hydroplaning, light reflection (albedo), fuel economy, and the availability of open traffic lanes (e.g., not closed for construction or maintenance) are of much greater interest to highway agencies and users. Future concrete pavement designs will be expected to provide all of these functional performance indicators to produce surfaces and structures that meet the needs and desires of highway agencies and users.
Monitoring concrete pavement performance indicators through PMSs is expected to be increasingly important to highway agencies in the future. It may become necessary to set up a performance feedback loop to provide continuous condition reports, making it possible to effect expeditious improvements to existing pavements not meeting users’ needs, as well as to improve the concrete pavement design procedures (particularly functional considerations related to surface characteristics), construction standards and specifications, and rehabilitation techniques.
Research is required immediately on the functional aspects of concrete highway performance, particularly to address a combination of tire-pavement noise, friction, smoothness, and other related factors. Note that an entire research track is devoted to this extremely important topic. Research is also needed for providing more rapid feedback and ways to schedule improvements related to surface characteristics and conditions. A critical need also exists for setting up feedback loops in highway agencies’ PMSs to monitor performance more effectively and rapidly and suggest improvements that minimize lane closures.
The traveling public will be provided with excellent pavement surface characteristics and a very high level of lane availability over the design life (i.e., minimal lane closures for maintenance or rehabilitation).
Pavement management and business systems objectives include the following:
Real-time pavement condition data that can be collected from concrete pavements include surface characteristics (friction, noise, distress, smoothness, etc.), climate, traffic, and structural factors. Data collection methods could include a combination of embedded electronics, highspeed assessment equipment, traffic measurement devices, and performance prediction equations. This program will require a new generation of equipment and standard test methods that address structural support, smoothness, friction, noise, moisture, drainage, and other factors.
Consistently, achieving successful pavement performance requires a systematic and integrated approach that considers all key aspects. It is not enough to have good design, construction, and materials selection individually to produce a reliable and cost-effective pavement. Even if each activity is done well by itself, it by no means guarantees successful pavement performance under the critical conditions that exist today. Consistently successful performance requires an integrated approach using mathematical models that compute the impact of each factor on stresses and deflections, and predict the damage related to distress and various functional conditions (e.g., smoothness, noise, and friction).
PMSs do not provide feedback data adequate for improving concrete pavement performance. Many such systems cannot even relate performance-monitoring data to original construction project information and traffic data. This critical gap can be remedied by developing improved data measurement and storage systems that not only provide this information rapidly, but also help analyze it. The goal of these new systems would be to provide rapid feedback to both schedule improvements in response to user feedback and continuously improve design, construction, materials selection, rehabilitation, and other aspects affecting performance.
Many aspects of design, construction, materials, and rehabilitation need further validation. Moreover, many innovative ideas are never tested because of the risks and costs of failure. Conducting full-scale testing or, in some cases, testing at existing ALFs, would provide a rapid and efficient means to meet both validation and testing needs. Some performance data, such as information on early opening of a roadway to traffic, can be gathered using ALFs (testing machines in buildings). Other data would need full-scale outdoor traffic testing using regular mixed traffic (similar to the Minnesota Road Research Project (Mn/ROAD)) or special trucks (similar to WesTrack vehicles). This plan would provide an excellent way to test new and innovative ideas for concrete pavement design, construction, and rehabilitation. A significant need exists to both supplement and build on the results from LTPP studies and sites such as Mn/ROAD.
The impact of today’s concrete pavement preservation alternatives (e.g., diamond grinding, dowel bar retrofit, and joint and crack resealing) on future life and performance is not fully understood and accepted. Establishing full-scale test sections under actual traffic loadings of innovative preservation activities would provide valuable information to establish the cost and benefits of such activities. These tests would build on information gained through the limited LTPP studies (Specific Pavement Studies (SPS)-4 and SPS-6). Since it is believed that welltimed preservation activities can be used to extend the service life of concrete pavements cost effectively, this is a significant gap that can be filled with appropriate research studies.
In most markets, concrete pavements are generally considered a high-priced option compared to asphalt solutions when examining initial costs, but they are equal or lower in price when addressing life-cycle costs. This is the generally accepted norm given current design procedures. Few tools exist, however, to effectively determine the true initial costs and price of items such as joints, sealers, and tie bars in various designs in specific projects. Most estimating is based on previous bid estimates. In addition, long-term analyses in life-cycle costs lack knowledge on which to improve maintenance analyses and user impacts.
Over the past several years, interest has grown in looking at corridors or areas rather than projects. This requires a new analysis technique that studies pavements at different stages of life, but if examined in a way to mitigate traffic shutdowns, it might require multiple fixes on a single project.
In addition, alternative contracting techniques, such as design-build, best value, and warranties, have cost implications that have not been studied or consolidated. The need is especially strong to examine the relationship of risk to the concrete pavement designer/builder and how best to equalize or at least quantify the risk. If the use of warranties continues to grow with or without maintenance requirements, then new bonding, insurance, and guarantee mechanisms need to be explored. Roles between government and industry are changing, so tools need to be developed that equitably evaluate the risks.
Interest is growing in public-private partnerships in which investors consider financing capital expenditures in return for either real or shadow tolls. Pavement costs could run 40–60 percent of a capital expenditure, with various options having a major impact when compared to traffic and tolling. Different concrete pavement solutions must be examined to balance initial cost, maintenance, traffic growth, and toll revenues.
Information is transferred too slowly to policymakers, engineers, and the concrete paving workforce. The concrete paving industry lacks innovation because of both the return on investment and the considerable time it takes to transfer innovation into practice across the United States.
Topics: research, infrastructure, pavements and materials
Keywords: research, infrastructure, pavements and materials, Dynamic modulus, MEPDG, LTPP, Hot mix asphalt, Artificial neural network (ANN)
TRT Terms: research, facilities, transportation, highway facilities, roads, parts of roads, pavements