Guidelines for the Preservation of High-Traffic-Volume Roadways (2011)

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C H A P T E R 1 IntroductionBackground Since the early to mid-1990s, pavement preservation has grown from an obscure term to standard practice in most highway agencies. Each practitioner may approach this from a different vantage point, but at various times the driving forces behind this shift have included one or more of the following: • A desire to improve overall pavement performance; • Greater attention to customer satisfaction; • Rising rehabilitation costs and constrained budgets; and • A need to improve safety in a cost-effective manner. Many agencies associate preservation with commonly used preventive maintenance treatments. As such, treatments such as chip seals or seal coats, crack filling, and slurry seals are synonymous with pavement preservation. Furthermore, these same treatments are almost always used on lower-volume roads. Inevitably, a strong link has developed between pave- ment preservation, preventive maintenance, and low-volume roads, even if it is purely circumstantial. Nothing intrinsically limits pavement preservation to lower- volume roads, however. In terms of pavement performance, the same nonload factors that contribute to the deterioration of low-volume roads contribute to the deterioration of high- volume roadways. Similarly, most preservation treatments will have the same beneficial effects on a pavement regardless of traffic volumes. Even though higher traffic volume will have more effect on the structural aspect of the pavement, preservation will slow or retard the structural deterioration. At the same time, it is recognized that there exist barriers to greater use of preservation treatments on high-traffic-volume roadways. Among these barriers are the following: • Shorter available construction windows; • Increased risk of failure associated with durability of treat- ment under higher traffic volume;1• Greater liability associated with failure; • Negative public perceptions associated with certain treat- ments; • Increased performance expectations; and • Lack of agency experience. The result is that where one agency will not use a certain treatment on pavements with average daily traffic (ADT) above 1,500 vehicles/day (vpd), another agency uses the same treat- ment routinely on pavements with ADT up to 20,000 vpd and higher. None of these barriers is insurmountable, but each requires a targeted effort to address and overcome. A part of that effort is addressed in SHRP 2 Renewal Project R26: Preservation Approaches for High-Traffic-Volume Roadways. A primary objective of the project is to improve pavement preservation practices on high-traffic-volume roadways. One way that objective is being met is in the development of guidelines that can be used to preserve high-volume roadways in ser- viceable condition for longer periods of time, at a lower cost, in a safer manner, and with limited disruption to the traveling public. Purpose The purpose of these guidelines is to provide direction to agen- cies on the selection and use of preservation treatments for high-traffic-volume roadways. These guidelines are based in large part on agency experience and practice, as provided in response to a detailed survey of practice and supplemented by the current practices gleaned from collected literature. It is expected that agencies using these guidelines will be able to extend their use of pavement preservation on high-traffic- volume roadways through a greater familiarity with the described treatments. Users of these guidelines should be aware that achieving the desired results from pavement preservation is dependent upon

2many interacting factors, including proper project selection, materials availability and quality, contractor capabilities, con- struction practices, and ambient conditions at the time of placement. Users interested in applying these guidelines to identify applications with which they do not currently have experience are encouraged to collect additional information regarding the best practices of experienced users to achieve the best possible outcome. Definitions The proper application of these guidelines depends in part on an understanding of common terms used throughout the doc- ument. Terms such as “preservation” and “preventive main- tenance,” as well as other terms related to their use, are often used inconsistently, fostering misconceptions about the appli- cability of pavements and the selection of treatments. There- fore, the definitions of relevant terms are presented in this section to provide a consistent interpretation of all information presented in the guidelines. Additional definitions of terms are given in Appendix A. • Pavement preservation. A network-level, long-term strat- egy that enhances pavement performance by using an inte- grated, cost-effective set of practices to extend pavement life, improve safety, and meet motorist expectations (Geiger 2005). Pavement preservation programs normally include a combination of preventive maintenance, minor rehabil- itation, and routine maintenance work. However, the major- ity of work under typical pavement preservation programs is focused on preventive maintenance. • Preventive maintenance. A planned strategy of cost-effective treatments applied to an existing roadway system and its appurtenances that preserves the system, retards future deterioration, and maintains or improves the functional condition of the system (without significantly increasing the structural capacity) (Geiger 2005). As illustrated in Fig- ure 1.1, preventive maintenance activities are performed in the early years of a pavement’s life, before the onset of sig- nificant structural deterioration. Example activities include crack sealing and filling, joint resealing, slurry seals, and chip seals. • Minor rehabilitation. Nonstructural enhancements (e.g., thin hot-mix asphalt [HMA] overlay, mill and thin HMA overlay) made to an existing pavement section to either eliminate age-related, top-down surface cracking that devel- ops in flexible pavements due to environmental exposure or to restore functionality of concrete pavements. Because of the nonstructural nature of minor rehabilitation tech- niques, these types of rehabilitation techniques are placed in the category of pavement preservation (Geiger 2005). As shown in Figure 1.1, minor rehabilitation generally occursSource: Adapted from Peshkin et al. 2007. Preventive Maintenance Reconstruction Good Poor Rehabilitation Time (years) Routine/Corrective Maintenance Minor Rehab Major Rehab Preservation Figure 1.1. Relationship between pavement condition and different categories of pavement treatment.in the early to middle years of a pavement’s life, when serviceability/ride quality issues become apparent. • Routine maintenance. Planned work that is performed on a routine basis to maintain and preserve the condition of the highway system or respond to specific conditions and events that restore the highway system to an adequate level of service (Geiger 2005). Crack filling and sealing and drainage maintenance are preservation activities that can be classified as routine maintenance. These and other rou- tine maintenance activities are often performed through- out a pavement’s life, as indicated by Figure 1.1. • Corrective maintenance. Maintenance activities per- formed in response to the development of a deficiency(ies) that negatively impacts the safe, efficient operations of the facility and future integrity of the pavement sections (Geiger 2005). Corrective maintenance (sometimes referred to as reactionary maintenance) is usually performed to fix a local- ized defect(s) due to unforeseen conditions and restore a pavement to an acceptable level of service. Example activities include pothole patching and concrete slab replacements. Corrective maintenance can be performed throughout a pavement’s life, as indicated by Figure 1.1. • Major rehabilitation. Structural enhancements that extend the service life of an existing pavement or improve its load-carrying capability or both (Geiger 2005). • Reconstruction. Replacement of the entire existing pave- ment structure with the equivalent or increased pavement structure. Reconstruction usually requires the complete removal and replacement of the existing pavement struc- ture. It may incorporate either new or recycled materials. Reconstruction is required when a pavement has either failed or has become functionally obsolete (Geiger 2005). • High-traffic-volume roadway. These are rural roadways with ADT values greater than 5,000 vpd and urban road- ways with ADT values greater than 10,000 vpd.

3• Surface type. The type of pavement on the top or surface of a pavement structure. For this study, the preservation approaches developed for high-traffic-volume roadways provide options for both HMA and portland cement con- crete (PCC) surface types. HMA-surfaced pavements include HMA on granular or stabilized base and HMA on PCC base (i.e., composite pavement). PCC-surfaced pavements include jointed plain concrete (JPC), jointed reinforced con- crete (JRC), and continuously reinforced concrete (CRC) pavements. • Treatment type. A specific work activity performed on a roadway pavement that is intended to treat one or more of the pavement’s deficiencies. Examples include crack seal- ing, thin HMA overlay applications, and diamond grind- ing. In some cases, a combination of treatments may be needed to treat existing deficiencies • Treatment category. A group of treatments with similar overall objectives and applied at similar times (Figure 1.1). For example, as described, preventive maintenance treat- ments are intended to preserve pavement integrity and prevent or retard future pavement deterioration. Other treatment categories include routine maintenance, minor rehabilitation, major rehabilitation, and reconstruction. • Distresses. Visible indicators of pavement deterioration caused by factors such as load, environment, construction practices, materials, support conditions, design practices, or, most commonly, a combination of two or more ofthese. Distresses can be further divided into two broad cat- egories, functional and structural:  Functional distress. Deterioration that affects the abil- ity of the pavement to provide a safe, smooth, and quiet surface for driving. Most functional problems can be corrected with preservation treatments if there is no serious underlying structural problem.  Structural distress. Deterioration caused by excessive loading, insufficient thickness, or lack of structural sup- port. Pavements with considerable structural distress are not good candidates for preservation treatments. Organization of the Guide This guide consists of three chapters and two appendixes. Fol- lowing this introductory chapter, Chapter 2 discusses some key factors that affect the selection of a pavement-preservation project and treatment, including traffic level, existing pave- ment condition, climatic condition, available work hours, and treatment performance and cost. Chapter 3 presents the treat- ment selection process, beginning with the identification of candidate treatments and ending with the treatment selection based on various economic (including cost-effectiveness) and noneconomic factors. Appendix A contains one- to two-page technical summaries for the various preservation treatments. Appendix B provides two example exercises intended to illus- trate certain portions of the treatment selection process.