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Preservation Approaches for High-Traffic-Volume Roadways (2011)

Chapter: Chapter 2 - Information Gathering and Review

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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
×
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
×
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
×
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
×
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
×
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
×
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
×
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
×
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
×
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
×
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Suggested Citation:"Chapter 2 - Information Gathering and Review." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
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Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

This chapter discusses the state of the practice with regard to preservation approaches for high-traffic-volume roadways. The content is based on two primary sources: a literature review and responses to a survey of the practices of state and other highway agencies. The chapter begins with a brief description of the information-gathering process and concludes with the state-of-the-practice synthesis organized around the following items: • Types of preservation treatments used on high-traffic- volume roads; • Special considerations for high-traffic-volume treatments; • Performance of treatments on high-traffic-volume facilities; and • Cost-effectiveness of preservation treatments. Information Gathering Literature Search A comprehensive literature search was conducted at the outset of the study and focused on information pertaining to pavement preservation practices and experiences. This search, largely limited to work reported in the last 5 years, was national and international in scope and was performed primarily via the Internet and through manual searches of the libraries, files, and other resource materials of the individual project team members. Among the key sources tapped in the literature search were the following: • Transportation Research Information Services (TRIS) database. • National Technical Information Service (NTIS) database. • Engineering Index and Compendix. • National Transportation Library (NTL). • Transportation Research Board (TRB) and TRB Research in Progress database. • American Association of State Highway and Transportation Officials (AASHTO). • Federal Highway Administration (FHWA) and National Highway Institute (NHI). • State department of transportation (DOT) research libraries. • Pavement preservation centers:  Foundation for Pavement Preservation (FP2);  National Center for Pavement Preservation (NCPP); and  California Pavement Preservation Center (CPPC). • National pavement centers:  National Center for Asphalt Technology (NCAT); and  National Concrete Pavement Technology Center (CP Tech Center). • Industry associations:  National Asphalt Pavement Association (NAPA);  Asphalt Institute (AI);  Association of Asphalt Paving Technologists (AAPT);  American Concrete Pavement Association (ACPA);  Portland Cement Association (PCA);  International Slurry Surfacing Association (ISSA);  Asphalt Recycling and Reclaiming Association (ARRA); and  International Grooving and Grinding Association (IGGA). • American Society of Civil Engineers (ASCE). • Innovative Pavement Research Foundation (IPRF). • American Society for Testing and Materials (ASTM). • International Organization for Standardization (ISO). • Transportation Association of Canada (TAC). • International Road Federation (IRF). • World Road Association (PIARC). • Australian Road Research Board (ARRB). • Laboratoire Central des Ponts et Chaussées (LCPC; French public works research laboratory). C H A P T E R 2 Information Gathering and Review 9

More than 100 documents were identified and compiled for use in this study, either in electronic or hardcopy form. Each of the selected documents was catalogued and reviewed in greater detail. Appendix A contains an annotated bibliography of several key documents. Key aspects of the literature review are included in the summary provided later in this chapter. Survey of Practice The literature search was supplemented with an electronic questionnaire distributed to SHAs, Canadian provinces, high- way agencies of several large cities, international practitioners, and several industry representatives. The purpose of this survey was to identify pavement preservation practices on rural and urban roadways, distinguished by surface type—HMA or PCC—and high traffic levels (as defined by the reporting agency). The survey focused on the following topics: • Successful techniques for pavement preservation on high- traffic-volume roadways currently in use; • Potentially successful techniques for pavement preservation approaches that are not yet fully deployed; • Challenges and solutions to implementation on high-traffic- volume roadways; and • Special considerations for quality control and quality assur- ance (QC/QA). Recognizing that the definition of “high-traffic-volume roadways” is perhaps as much or more a matter of perception as it is a matter of policy, the survey also asked the respondents to define what traffic volumes fell in that category for them. The questionnaire included the preservation treatments shown in Table 2.1. It called for respondents to link these treatments to roadways, differentiating by traffic volume and rural-versus-urban route, as well as matching closure time scenarios to treatment, indicating which pavement perfor- mance issues are addressed by each treatment, and which contracting mechanisms are used to ensure quality. Further- more, it sought feedback concerning why certain treatments are not used by the responding agency (e.g., lack of experience, bias against, previous failures, cost, safety issues, and so on). To reduce the time required to fill out the 24-page question- naire, it was developed and administered using InstantSurvey, an online software tool that creates, distributes, manages, and analyzes online surveys. The time period required for complet- ing the survey was approximately 8 weeks. The complete survey is provided in Appendix B, and a detailed breakdown of the responses is provided in Appendix C. Key aspects of the survey results are included in the summary provided later in this chapter. Analysis and Summary of Collected Information Literature Review This section provides a summary of the pertinent literature reviewed in the first phase of the study. The information presented is intended to familiarize the reader with the key aspects regarding the use of preservation treatments on high-traffic-volume roadways. The information was used in conjunction with information from additional pieces of literature collected in the second phase of the study to aid the development of the preservation guidelines featured in Guide- lines for the Preservation of High-Traffic-Volume Roadways. Pavement Preservation Overview One definition of pavement preservation is that it is a planned system of treating pavements at the optimum time to maximize 10 Table 2.1. Common Pavement Preservation Treatments HMA-Surfaced Pavements PCC-Surfaced Pavements Crack fill Crack seal Cape seal Fog seal Scrub seal Slurry seal Rejuvenators Microsurfacing Single course Multiple course Chip seal Single course Multiple course With polymer-modified binder Ultra-thin bonded wearing course Thin HMA overlay (<1.5 in.) Cold milling and thin HMA overlay Ultra-thin HMA overlay (<0.75 in.) In-place HMA recycling Hot (<1.95 in.) Cold (<4.0 in.) Profile milling (diamond grinding) Ultra-thin whitetopping Drainage preservation Note: 1 in. = 25.4 mm Joint resealing Crack sealing Diamond grinding Diamond grooving Pavement patching Partial depth Full depth Dowel bar retrofit (i.e., load transfer restoration) Thin PCC overlay Ultra-thin bonded wearing course Thin HMA overlay (<1.5 in.) Drainage preservation

their useful life, thus enhancing pavement longevity at the lowest cost (Kuennen 2006b). It represents a proactive approach to maintaining existing highway pavements that enables high- way agencies to reduce costly, time-consuming rehabilitation and reconstruction projects and the associated traffic disrup- tions (Geiger 2005). Table 2.2 illustrates various pavement activities and their primary purpose. The three shaded rows represent pavement preservation, indicating that it is composed of PM, some forms of minor (nonstructural) rehabilitation, and some forms of routine maintenance (Geiger 2005). The darker shading indicates that PM is the primary component of pavement preservation. The general philosophy of pavement preserva- tion is to apply preventive (actions intended to prevent, stop, or slow down deterioration), restorative (actions intended to improve conditions or restore conditions to acceptable levels), or limited corrective (actions intended to fix defects or reestab- lish structural integrity) treatments to pavements that are in relatively good condition and have little or no structural dete- rioration. Application of the right treatment at the right time and in the right manner can help prolong the service life of the pavement. Incidentally, this is especially important for high-traffic-volume roadways where construction delays have a large impact on users. One of the keys to an effective pavement preservation pro- gram on high-volume roadways is understanding pavement performance. The typical life cycle of a pavement and the gen- eral categories of treatments that are appropriate at different times of the life of the pavement are presented in Figure 2.1. PM is used early in the life of the pavement, while the pavement is still in good condition. When a pavement has deteriorated so that more extensive cracking and other distresses are present, the use of PM is no longer appropriate, but it could be too soon to trigger major rehabilitation. Pavements at this condition level receive minor rehabilitation treatments, such as thin overlays or surface recycling, that restore functional qualities and, to a limited extent, structural integrity. The use of PM treatments and minor rehabilitation techniques along with routine maintenance are good options for a pavement that is still in relatively good condition. If PM or minor rehabilitation is not used during the life of the pavement, the pavement will deteriorate to the point that major rehabilitation (structural restoration, such as full-depth repairs or thick overlays, or even reconstruction) is necessary. When a pavement develops significant levels of distress, pavement preservation activities are no longer viable treatment options. If PM or minor rehabilitation is used on a pavement that is highly deteriorated, the life of the chosen treatment can be greatly reduced, especially on pavements with high traffic volumes. 11 Table 2.2. Classification of Pavement Activities by Purpose Purpose of Activity Restore Surface Improve or Restore Type of Activity Increase Capacity Increase Strength Slow Aging Characteristics Functionality New construction X X X X X Reconstruction X X X X X Major (heavy) rehabilitation X X X X Structural overlay X X X X Minor (light) rehabilitation X X X Preventive maintenance X X X Routine maintenance X Corrective (reactive) maintenance X Catastrophic maintenance X Source: Adapted from Geiger 2005. Source: Adapted from Peshkin et al. 2007. Preventive Maintenance Reconstruction Good Poor Rehabilitation Time (years) Routine/Corrective Maintenance Minor Rehab Major Rehab Preservation Figure 2.1. Relationship between pavement condition and different categories of pavement treatment.

Preservation Treatments There is a broad range of treatments that may be used in the preservation of pavements. While many may focus on a specific treatment and its role in preservation, it is not the treatment alone that defines preservation. Considering Table 2.2 and Figure 2.1, both the purpose and timing of the treatment help define a preservation treatment. With that caveat, descriptions of treatments that are commonly used in pavement preservation are provided in the Guidelines for the Preservation of High- Traffic-Volume Roadways. In addition to the treatments listed in the Guidelines for the Preservation of High-Traffic-Volume Roadways, drainage preservation is a treatment that can be carried out on both HMA- and PCC-surfaced pavements. This activity consists of cleaning silt, debris, and vegetation at underdrain outlets and replacing damaged or destroyed outlets. Although not directly applied to the pavement structure, it is considered by many to be an essential tool in the preservation of the pavement, as it helps to ensure adequate drainage of the structure. A few other types of preservation treatments were identified and examined as part of the literature review. These treat- ments fall under one or another of the following categories: (a) lengthy existence but limited overall use; (b) lengthy exis- tence but use limited to one or two agencies; (c) international use, with recent trials in the United States; or (d) new or inno- vative, with recent trials in the United States. Known details regarding each of these treatments are provided below. Each preservation treatment has unique capabilities and functions that enable them to accomplish the following: • Prevent or delay the occurrence of new distresses or slow the development of existing distresses; or • Restore the integrity and functionality or serviceability of the pavement or improve its surface characteristics. The primary means by which the treatments can achieve these goals are summarized in Tables 2.3 and 2.4. Preservation Treatments and Existing Pavement Condition The condition of a pavement has a significant impact on the ability of treatments to fulfill their respective goals, and so their effectiveness is fairly variable. By the same token, a treatment will not be very effective if the pavement condition is too good, although that “problem” is rarely encountered. While it is difficult to establish optimal timings (in terms of the overall condition of the existing pavement) for the appli- cation of individual treatments, the timings of treatments grouped according to similar goals and purposes are easier to construct. Preventive treatments like joint or crack sealing and surface seals are most appropriate for pavements in good to very good condition, while preventive or restorative measures like thin HMA overlays, proprietary surfacings, and patching are most appropriate for pavements in fair to good condition. More extensive restorative treatments like mill-and-HMA overlay, ultra-thin whitetopping, thin PCC overlays, and partial-depth recycling (i.e., hot in-place recycling [HIR] and cold in-place recycling [CIR] confined to surface, intermediate, or upper-base layers) are most appropriate for pavements in fair condition. The selection of appropriate preservation treatments is based not only upon the overall condition of the roadway, but also the specific visible distresses. For instance, if transverse crack- ing in an HMA-surfaced pavement is frequent but there is not a high degree of edge deterioration, the pavement may be best treated with a surface treatment. If the cracks are low to moderate in frequency but have typically progressed to a point of high edge deterioration, then crack repair or patching may be needed. In the case of pavements with transverse thermal or reflection cracks that are moderate in density and have little or no deterioration, the cracks can be treated effectively through sealing operations. For pavements with a substantial amount of nonworking cracks (primarily longitudinal, but also transverse) with different size openings and relatively low levels of dete- rioration, an appropriate treatment is crack filling. Thin HMA overlays are used on all types of roadways for functional improvements. The pavement to be restored using thin HMA overlays should be in good to fair condition. This type of treatment is particularly suitable for high-volume roads in urban areas where longer life and relatively low-noise surfaces are desired. Similarly, slurry seals do not usually per- form well if the underlying pavement contains extensive cracks. According to the South Dakota DOT, slurry seals should not be used on deteriorated pavements. Chip seals, on the other hand, can be applied during the majority of a pavement’s life (Johnson 2000). However, the ideal benefits of chip sealing are achieved when the treatment is applied early. For instance, chip sealing can be used when the pavement has just begun to oxidize, and should not be applied to pavements with distress such as high-severity cracking, raveling, potholes, or rutting. Additionally, for the use of thin HMA overlays, cracking should be of low to moderate severity and ideally should have been crack-sealed 6 to 12 months prior to the thin overlay application. Raveling should be of low to moderate severity, with depressions caused by stripping of the surface no greater than 0.25 in. (6 mm) deep. In addition, it is recommended to mill the surface before an overlay application when segregation, raveling, or block cracking are present (Hein and Croteau 2004). If rutting is evident, the pavement can also receive a leveling course instead of milling. Also identified in the literature search, ultra-thin bonded wearing course applications are typically used to seal the surface 12

13 Table 2.3. Primary Capabilities and Functions of Preservation Treatments for HMA-Surfaced Pavements Prevention Restoration Improve Profile Seal/Waterproof Rejuvenate Surface/ Eliminate Eliminate Improve Texture (Lateral Surface Improve Texture Treatment Pavement Inhibit Oxidation Surface Defectsa Stable Ruts for Friction Drainage and Ride) for Noise Crack filling   Crack sealing   Cold milling   Profile milling    Rejuvenation  Fog seal   Scrub seal    Slurry seal    Microsurfacing      Sand seal    Chip seal     (minor) Ultra-thin HMAOL      Ultra-thin bonded wearing course      Thin HMAOL Dense-graded       Open-graded (OGFC)b  Gap-graded (SMA)     Mill and thin HMAOL       Hot in-place recycling Surface recycling     Remixing     Repaving     Cold in-place recycling     Ultra-thin whitetopping     Source: Modified from KYTC 2009. Note: HMAOL = Hot-mix asphalt overlay; OGFC = Open-graded friction course; SMA = Stone matrix asphalt. a Surface defects include weathering/raveling, bleeding, polishing, surface cracks, and so on. b Improves splash/spray.

to minimize weathering, raveling, and oxidation. Candidate roads for this treatment usually should have ruts less than 0.5 in. deep, moderate to no cracking, and minor to no bleed- ing. In contrast, slurry seals are used to seal the surface of the existing asphalt pavement, retard surface raveling, seal small cracks, and improve surface friction. As with other surface treatments, slurry seals should not be used where sealing the pavement would cause a stripping problem or where the under- lying pavement is cracked (Wade et al. 2001). Other preventive treatments include fog seals, which can be considered a candidate treatment to address raveling, and oxidation. However, a fog seal generally lasts only 1 to 2 years. Microsurfacing is primarily used as a surface seal to address rutting and loss of friction; this treatment also limits damage from water, oxidation, and ultraviolet (UV) rays, which cause weathering, raveling, and surface cracking. A detailed analysis of the long-term pavement performance (LTPP) data from the four treatments used at SHRP Specific Pavement Study (SPS)-3 sites through 2001 indicated that thin HMA overlays were most effective—followed by chip seals and then slurry seals—in addressing roughness, rutting, and fatigue cracking (Hall et al. 2002). Slurry seals showed no effect on long-term roughness. The thin overlays, as expected, were the only treatment to affect long-term rutting. The study concluded that, with respect to roughness, rutting, and crack- ing on PCC pavements in the SPS-6 study, HMA overlay had the best effect, followed by diamond grinding, full-depth repair, and joint and crack sealing. No added benefit was associated with drainage improvement, dowel bar retrofitting, and undersealing. Regarding the use of diamond grinding on concrete pave- ments, the pavement should not have corner breaks, spalling, or popouts. The visible surface distress may include low- severity cracking, faults not exceeding 0.25 in. (6 mm), and moderate to severe polishing. Pavements with moderate to advanced material-related distresses, such as alkali-silica reaction (ASR) and D-cracking, are not good candidates for diamond grinding (Shuler 2006). Use of Preservation Treatments on High-Traffic-Volume Facilities While it is generally observed that the practice of pavement preservation and the use of PM are growing among trans- portation agencies, the majority of constructed preservation projects, in terms of treated lane miles, occur on lower-volume roadways. One explanation for this is that typical PM treat- ments, such as chip seals and other thin surface treatments, have historically been used on low-volume roads. However, there are many indications that this is changing. A 2004 survey conducted under the National Cooperative Highway Research Program (NCHRP) 20-07 revealed that most agencies practice pavement preservation on all types of facilities (Peshkin and Hoerner 2005). This conclusion was drawn from responses to the following question, “On what facility types does your agency currently apply preven- 14 Table 2.4. Primary Capabilities and Functions of Preservation Treatments for PCC-Surfaced Pavements Prevention Restoration Prevent Improve Profile Seal/Waterproof Intrusion of Remove/Control Improve Texture (Lateral Surface Improve Texture Treatment Pavement Incompressibles Faulting for Friction Drainage and Ride) for Noise Crack sealing   Joint resealing   Diamond grinding     Diamond grooving  Partial-depth patching     Full-depth patching   a a Dowel bar retrofit   Ultra-thin bonded      wearing course Thin HMAOL      Thin PCCOL      Source: Modified from KYTC 2009. Note: HMAOL = Hot-mix asphalt overlay; PCCOL = Portland cement concrete overlay. a In conjunction with diamond grinding.

tive maintenance treatments?” The responses are shown in Table 2.5. Results from this survey seemed to indicate that pavement preservation is occurring as frequently, or even more frequently in the case of rural roads, on higher-volume roadways as on lower-volume roadways. These results suggested that the more important distinction is between rural and urban roadways for any traffic volume. Although in general there may be a common association between typical preservation treatments and their use on low- volume roads, some departments of transportation (DOTs) are finding it effective to apply such treatments to high-volume roads. The DOTs identified in the literature as having per- formed preservation work on high-traffic-volume roadways (ADT ≥ 2,500 vpd) include Alabama, Arkansas, California, Colorado, Florida, Georgia, Idaho, Montana, Oklahoma, Oregon, Pennsylvania, South Dakota, Texas, Utah, Virginia, and Washington State. International agencies proactive in the use of preservation treatments on high-volume roads include the United Kingdom, South Africa, Spain, France, and Australia. While chip seals have seen the greatest use on low-volume roadways (with a typical ADT less than 1,000 vpd), California allows them to be used on roads with average annual daily traffic (AADT) up to 30,000 vpd (Romero and Anderson 2005). The United Kingdom “commonly” uses chip seals on roads with ADT greater than 20,000 vpd, as do Colorado and Montana (Cuelho et al. 2006). In Washington State, chip seals were used on the Tacoma Narrows Bridge, which has an ADT of 178,000 vpd (Kuennen 2006a). Following the successes of other states, a study conducted for the Utah DOT recommended that chip seal usage extend to “certain roads with AADT up to 20,000 vehicles,” while continuing the existing practice of using chip seals on high- way sections with AADT less than 5,000 vpd (Romero and Anderson 2005). On the other hand, while the Colorado DOT’s maintenance superintendents believe chip seals “can be used on high-volume roads (AADT up to 10,000 vpd),” one region restricts their use to roads with AADT less than 1,200 vpd, and Ohio limits their use to roads with less than 2,500 vpd AADT (Galehouse 2004; Ohio DOT 2001). In other states, such as Utah, there was some concern about cost and relative performance of chip seals; following a life-cycle study of chip seals, it was recommended that policies be modified to specify open-graded friction courses (OGFCs) for high-speed (greater than 55 mph [88 kph]), high-volume roads (AADT greater than 25,000 vpd), similar to practices in Georgia, Nevada, and Oklahoma (Romero and Anderson 2005). OGFCs have also found success on high-volume roads in Florida (at 10 to 12 years) and Oregon (up to 8 years and 2.5 million equivalent single-axle loads [ESALs]) (Huddleston et al. 1993; Page 1993). At the same time, Connecticut and South Carolina limit the use of OGFCs, and other states, including Illinois, Michigan, and Washington, have discontinued their use because of poor performance. Microsurfacing has been successful on high-volume roads in Texas, Kansas, Oklahoma, Pennsylvania, and Arkansas. Oklahoma found that microsurfacing provides adequate performance for “at least 4 years under traffic volumes up to 70,000 ADT” (Raza 1994). Virginia has applied microsurfacing treatments to stretches of Interstate with AADTs ranging from 14,000 up to 26,000 vpd, preserving “performance qualities for several years,” whereas Michigan confirms this level of performance, typically assuming service life for a single-course microsurfacing treatment of 3 to 5 years or up to 6 years for multiple courses (Morian et al. 2005; Peshkin and Hoerner 2005). Indiana has determined that “severe climatic condi- tions,” as opposed to traffic volume, have a greater effect on performance of microsurfacing treatments (Labi et al. 2007). Cold in-place recycling (CIR), has found success in Pennsylvania, where projects have outperformed their expected service life of 10 years by an average of 3 additional years (Morian et al. 2004). In Nevada, with regular crack sealing and judicious use of CIR, projects can achieve full life expectancy of 15 to 20 years (Bemanian et al. 2006). In Quebec, Canada, 15 Table 2.5. Summary of Facility Characteristics Associated with Projects Selected as Candidates for Pavement Preservation Projects General ADT Range Associated with Number of Respondents Different Roadway Classifications Using Preservation Roadway Classification (vehicles per day [vpd]) Rural Urban Freeway 30,000 and above 29 of 35 (83%) 26 of 35 (74%) Arterial 12,000 to 40,000 29 of 35 (83%) 27 of 35 (77%) Collector road 2,000 to 12,000 29 of 35 (83%) 27 of 35 (77%) Local road ≤2,000 24 of 35 (69%) 22 of 35 (63%) Source: Peshkin and Hoerner 2005.

Bergeron (2005) compared CIR practices with typical asphalt resurfacing for highways with AADT of 20,000 vpd to deter- mine the difference in net present value and benefit-cost ratio. The additional performance of CIR compared with asphalt resurfacing resulted in higher benefit-cost ratios, even though the net present values were higher for CIR. Bergeron also found that CIR net present values for national and regional roads (with an AADT of 12,000) were less and had even higher benefit-cost ratios. Ultra-thin bonded wearing courses (also referred to as ultra-thin friction courses) are a relatively new preservation treatment but are generally considered appropriate for high- volume roads. The literature identifies performance studies in two southern states, Alabama and Louisiana. Alabama has had success using ultra-thin bonded wearing course on sev- eral high-volume roads including US 280 (13,000 ADT), AL 21 (7,500 ADT), I-65 (60,000 ADT), and I-29 (165,000 ADT) (Koch 2001). Missouri’s first experiment using this treatment was damaged by freeze-thaw and snowplowing (MoDOT 1999). This treatment has also been placed in several cold-weather states, including Colorado, Michigan, New York, Ohio, Penn- sylvania, and Wisconsin (Koch 2001). Anecdotal reports are that it has been successful. SPECIAL CONSIDERATIONS FOR HIGH-TRAFFIC-VOLUME TREATMENTS A common concern regarding preservation treatment per- formance on high-volume roads is the issue of treatment durability, or obtaining a cost-effective service life from the preservation treatment, given the traffic level. As previously asserted, effective preservation requires the appropriate treat- ment for a given pavement section, as well as proper timing (Geoffroy 1996). For high-volume facilities, choosing the appropriate treatment may require additional considerations. For example, as noted, chip seals see their most common application as wearing courses on low-volume roads, but they have proven successful as surface treatments for high-volume roads. Using a chip seal on a high-volume road may require using a higher-quality aggregate or polymer-modified binder, which has been effective for California and Washington State, with both reporting 5 to 7 years of serviceable life (Shuler 1998; Geoffroy 1996). Gransberg’s (2005) synthesis of chip sealing best practices found that all nine agencies (culled from 72 individual responses from 42 states and 12 cities and counties) reporting superior results from chip sealing applications do the following: • Use polymer or crumb-rubber modified binders; • Use pavement condition ratings as triggers, then select roads of moderate or less distress level with structural cross-section rated fair or better; and • Follow chip sealing applications with routine crack or fog sealing. Specifically regarding high-volume roads, Gransberg concluded: • Chip seals can be successfully used on high-volume roads if the agency’s policy is to install it on roads before pavement distress becomes severe or the structural integrity of the underlying pavement is breached. • Both hot asphalt cement and emulsified asphalt binders can be used successfully on high-volume roads. Binders modified by polymers or crumb rubber seem to reinforce success. Some other recommendations for applying chip seals to high-volume facilities include applying a “choke” aggregate to prevent dislodging larger aggregate chips or applying a fog or flush seal over the chip seal (Shuler 1998; Wade et al. 2001). One region in Colorado applies fog seals within 2 to 10 days of placement on a “majority” of chip seals (Galehouse 2004). However, it should be noted that additional time may be required to allow emulsions to break (Wade et al. 2001). Several additional considerations are recommended to extend the applicability of chip seal treatments to higher- traffic-volume roadways. These include the following (Beatty et al. 2002; Shuler 1998): • Precoat aggregate to improve adhesion, an approach popu- lar in South Africa and Australia. • Limit excess chips to 5% to 10%. • Sweep excess chips prior to opening to traffic. • Once opened to traffic, control speeds (via signage or a pilot car) to reduce whip-off and to promote embedment. In Canada, it has been confirmed that the structural integrity of the seal is “dependent on the embedment of the aggregate in the binder/substrate” because chip seals are leaner on high- volume roads to avoid bleeding (Croteau et al. 2005). PERFORMANCE OF TREATMENTS ON HIGH-TRAFFIC-VOLUME FACILITIES Performance is varied for different preservation treatments on high-volume roadways. California reports “good performance” from chip seals on facilities with up to 30,000 ADT, and “good performance” from crack sealing, slurry sealing, and microsurfacing, as well as applying OGFCs and thin HMA overlays for facilities with greater than 30,000 ADT. On the other hand, California does not recommend fog sealing on facilities with greater than 5,000 ADT, and has typically expe- rienced “fair performance” with fog seals on facilities with less than 5,000 ADT (Shatnawi et al. 2006). Texas monitored performance of different PM treatments on the SPS-3 sections (crack sealing, chip seals, slurry seals, and thin overlays), concluding that chip seals performed the 16

best under a “wide range” of pavement conditions, as well as scoring the best on high- and low-volume sections. Consider- ing initial cost, chip seal is a better choice on high-traffic roads, especially where rutting is not a concern. If rutting is a major problem, then a thin HMA overlay was determined to be the most effective option (Chen et al. 2003). Slurry seals have typical reported service lives of 3 to 5 years on roads with “moderate to heavy traffic,” effectively reducing crack development and raveling, as well as being “marginally effective” in preventing reflective cracking (Morian et al. 1997; Raza 1992). Flush seals are reported to survive “approximately 2 to 7 years” for traffic up to 5,000 ADT and up to 5 years for higher volumes (NCHRP 1997). Microsurfacing provided good rut resistance for 3 to 7 years in Kansas, Pennsylvania, Oklahoma, and Arkansas. Oklahoma and Pennsylvania also note good surface friction for up to 5.5 years of service (Raza 1994; Wade et al. 2001). However, in North Carolina, it was reported that once the microsurfaced sections failed, they “deteriorated quickly” due to the pavement’s diminished structural integrity under heavy traffic loading (Morian et al. 2005). OGFCs have reported service lives of 10 to 12 years on Florida Interstates and up to 8 years in Oregon (Huddleston et al. 1993; Page 1993). Reported average service lives for CIR treatments range from 5 to almost 13 years in Ohio and Pennsylvania (Hicks et al. 2000; Morian et al. 2004). Ultra-thin bonded wearing courses are generally reported to achieve service lives of between 7 and 12 years (Gilbert et al. 2004; Peshkin and Hoerner 2005). Illinois reports successful service lives of 7 to 10 years using thin HMA overlays (1 to 1.5 in. [25 to 38 mm]) when correctly targeting specific pavement condition criteria, while one district in Indiana expects a 10- to 15-year pavement life extension using thin HMA overlays (Cuelho et al. 2006; Reed 1994). Iowa DOT has also found best performance from thin HMA overlays compared to chip seals, fog seals, cape seals, slurry seals, and even microsurfacing (Jahren et al. 2003). Washington State DOT most commonly uses thin HMA overlays for pavement preservation, reserving chip seal applications for lower-traffic areas (Li et al. 2008). In Colorado, it was noted that deicer compounds leave residue in pavement cracks, preventing adequate sidewall adhesion and, consequently, loss of crack sealant. Seasonal limitations were recommended, including waiting “at least two rainfall events” before commencing crack-filling operations (Galehouse 2004). In Utah, OGFCs have on average survived 7 years, early failures being related to raveling, stripping, and potholing (Romero and Anderson 2005). The literature gives some indication of how extensively practitioners are making efforts to establish PM practices and policies for their high-traffic-volume roadways with varying degrees of success. The performance of treatments varies significantly from agency to agency, and there are gaps in the shared knowledge pool, especially regarding PM practices on PCC roadways. Furthermore, “success” is a relative concept, where what some agencies describe as successful is not con- sidered as successful by others. Variations in traffic, climate, and materials may account for some of these relative differences. In any case, the full extent of each agency’s PM program is difficult to gauge from the literature. In the next section, the review of the questionnaire responses illuminates state and provincial PM practices and can be viewed as a supplement to the information reported in the literature. Preservation Treatments and Climate Climate is commonly defined as the weather of a given region averaged over a long period of time (AMS 2008). It encom- passes the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, and numerous other meteorological elements, and is affected by latitude, terrain, altitude, ice or snow cover, as well as nearby water bodies and their currents. Climatic conditions impact preservation treatment usage in at least two ways: determining construction timing, and affecting treatment performance. Brief discussions of these impacts are provided in the following sections. CLIMATIC EFFECTS ON CONSTRUCTION TIMING Some treatments, especially those based on asphalt emulsions, are best applied under restricted temperature and humidity conditions. Climate can directly affect curing time, which in turn impacts treatment feasibility and opening to traffic. For example, crack sealing techniques are best applied when temperatures are moderately cool (i.e., spring and fall in the northern half of the United States). Accordingly, the Ohio DOT recommends that crack sealing, in contrast to most other PM strategies, be performed in cooler weather when the pavement has contracted, thus moderately expanding crack openings such that on very hot or cold days, the sealant will not bulge excessively or risk pulling away (Cuelho et al. 2006). Because crack filling treats nonworking cracks that are not significantly affected by temperature fluctuations, crack filling can be applied any time of the year when weather conditions are appropriate (i.e., no rain or snow). Fog seals, according to the South Dakota DOT, are not rec- ommended for high-volume roadways because of the length of time required for slow setting emulsions to break, which reduces the amount of surface friction immediately after application (Wade et al. 2001). The use of a slurry seal may not be appropriate for high- volume roads where traffic must be allowed very soon after application. In warm weather, slurry seals require at least 2 hours to cure, resulting in potential traffic delays. On the other hand, microsurfacing cures and develops strength faster 17

than conventional slurry seals and can be opened to rolling traffic in about an hour; therefore it is more applicable for a variety of environments. In the case of chip seals, cold-applied seals must be placed during the day and in warm temperatures, while hot-applied chip seals can be placed at night and in cooler temperatures. Generally, the construction season runs from May to September to take advantage of the warmest months for the northern states (Gransberg 2005). Good performance related to favorable climatic conditions during placement and also, importantly, favorable climatic conditions during the weeks following placement. The major cause of pavement failure is weather related, such as when rain or extreme temperatures occur shortly after construction (Croteau et al. 2005). Although thin HMA overlays can be placed successfully in a variety of climatic conditions, application in cooler tem- peratures can impact the ability to achieve specified density. This is particular true for ultra-thin HMA overlays. CLIMATIC EFFECTS ON TREATMENT PERFORMANCE Whereas some preservation treatments, such as diamond grinding on PCC pavements, may not be too affected by dif- ferences in climate, most treatments do experience climate- related performance effects. For example, the Indiana DOT has determined that severe climatic conditions, as opposed to traffic volume, have a greater effect on performance of certain treatments, such as microsurfacing (Labi et al. 2007). Results of the SHRP SPS-3 study indicated that chip seals performed well across all climate zones and very well in wet nonfreeze zones (Morian et al. 1998). Moreover, slurry seals showed very good performance in nonfreeze climates, but poor performance in freeze climates. Similarly, crack seals showed good performance in nonfreeze climates, but signif- icantly reduced performance in freeze climates. International Pavement Preservation Practices In addition to information on preservation practices within the United States, some information was obtained about international practices. The proper context for each treatment strategy must be understood because the way in which each country chooses its preservation strategy depends on its stan- dard road design, climate, traffic patterns, and political and economic organization. Information collected from Saudi Arabia, India, France, South Africa, and Australia is provided in the following descriptions. Note, however, that these are large, diverse countries and that what is reported may not be representative of an entire country’s practice. Saudi Arabia reported using sulfur asphalt, crack sealing, slurry seals, microsurfacing, and thin overlays as part of its preservation activities. Sulfur asphalt is a mixture of asphalt binder and a sulfur compound that makes a stiffer product. This product is more resistant to rutting, even with inferior aggregates, but due to its stiffer and more brittle nature, it can be susceptible to fatigue cracking and is less resistant to water damage and stripping than conventional asphalt. The tem- perature must be closely monitored during mixing to ensure the proper blend of asphalt and sulfur. The price and avail- ability of sulfur varies, making it difficult to predict prices and feasibility. Its uses are similar to any other asphalt overlay, except that layer thickness may be decreased when rutting is the primary concern. Rut-resistant solutions are important in the country’s hot climate. India has included in its pavement preservation strategies the use of stone matrix asphalt (SMA), microsurfacing, and cold in-place recycling. SMA is a type of HMA that uses a modi- fied aggregate gradation. This gap-graded gradation creates a stable skeleton of top-size aggregate particles, whereas the fine materials mix with the binder to create a stiff mastic to hold the aggregate skeleton together. Fibers are sometimes included. This stone-on-stone contact makes a highly rut-resistant material. Similar to the practices in Saudi Arabia, India has placed important emphasis on the development of rut-resistant asphalt mixes due to the hot climate. France reports on an overall pavement strategy that is focused on building strong and stiff underlying pavements and performing surface repaving every 10 to 15 years. As is common for many European countries, many of the roads and maintenance contracts in France are privatized, so the work may be performed and funded by private entities rather than by the government. Seals and thin overlays are used for improving skid resistance, reducing noise, and enhancing ride smoothness between major repaving projects. Open-graded mixes are commonly used for noise reduction. In material design, aggregate quality is emphasized, and both hot asphalt mixes and emulsions are used for surface work. A new devel- opment, called a “bio-binder,” which is asphalt cut back with vegetable oil to make a binder that is workable at normal tem- peratures, has been used on several projects, though full details of its performance are not known. South Africa uses a variety of surface seals, especially chip seals, even on high-volume roads. An important part of the process is that the aggregate is precoated to reduce loss and stripping. Like France, South Africa emphasizes aggregate quality by limiting fines and securing quality aggregate regard- less of cost. Also, like France, it builds strong and thick pave- ment sections, so that structural distresses are minimized and the use of chip seals address surface distresses only. Emulsions are used only for fog seals or rejuvenators; otherwise, hot asphalt is used. Crumb rubber is used in both HMA and surface treatments. Australia places a heavy emphasis on preservation, partic- ularly keeping water away from the subgrade. Most roads have a very thick subbase, a strong unbonded base course, 18

and an asphalt concrete wearing surface. An example of a PM process in Australia includes milling and placement of a stress-absorbing membrane, followed by an asphalt concrete overlay. Emphasis is placed on crack sealing with polymer- modified binder to prevent water intrusion. Another PM technique is a tack coat that is followed by a geotextile and then a chip seal. Most Australian states dedicate more fund- ing to PM than to reconstruction. For example, the state of Victoria dedicates 90% of its program to prevention and 10% to reconstruction. Review of Survey Results As shown in Table 2.6, 50 highway agencies responded to the pavement preservation questionnaire; the FHWA’s Central Federal Lands Highway Division (FHWA-CFLHD), National Association of County Engineers (NACE), and National Asphalt Pavement Association (NAPA) also provided responses. A review of the survey responses revealed that there was a wide range of experience in pavement preservation practices. Among the 28 agencies that responded to the experience question, one-half reported having more than 10 years of expe- rience and one-quarter reported having more than 20 years’ experience. Treatment Selection Considerations In identifying the important considerations in selecting pre- servation treatments, respondents collectively reported the following hierarchy: • High Priority 1. Safety concerns (76%) 2. Treatment cost (74%) 3. Durability/expected life of treatment (64%) • Medium Priority 1. Availability of experienced contractor (60%) 2. Work zone considerations (59%) 3. Tied: Risk associated with treatment failure; closure time (57%) • Low Priority 1. Availability of alternate route(s) (40%; however, one in four of all respondents considered this issue unimpor- tant) 2. Noise issues (39%) 3. Public perception (36%) Traffic volume was considered of high priority by just over half of respondents and of medium priority by approximately 40%. This implied that if pavement preservation is indeed practiced on high-traffic-volume roads, many agencies have established standard practices using preservation treatments for that application. Responses regarding the most successful treatments indi- cated that they have low cost, good durability and long life expectancy, and fast application (important in getting work crews quickly out of harm’s way and in minimizing impact on road users). These responses show the influence of the noted priority factors on treatment selection. On the other hand, the common complaints against the least successful preservation treatments that agencies have used were related to high cost and poor performance. Traffic Level and Treatment Use An important consideration affecting which preservation treatments are used on high-traffic-volume roadways is how the agency defines “high” traffic volumes. While some respon- dents wanted the researchers to provide a definition for high traffic volumes, it was recognized that different agencies use markedly different definitions and that it would be better for respondents themselves to provide this value. Accordingly, in 19 Table 2.6. Summary of Survey Respondents State Highway Agencies Canadian Provinces Alaska Montana Alberta Arizona Nebraska British Columbia Arkansas Nevada Manitoba California New Hampshire New Brunswick Colorado New Mexico Ontario Connecticut New York Quebec Florida North Carolina Saskatchewan Georgia Ohio Hawaii Oklahoma Cities Illinois Pennsylvania Phoenix, Ariz. Indiana Rhode Island San Diego, Calif. Iowa South Carolina Kansas South Dakota Toll Authorities Kentucky Tennessee Texas Turnpike Louisiana Texas Maine Utah (3)a Michigan Virginia Minnesota Washington Mississippi (4)a Wisconsin Missouri Wyoming a Agencies that submitted multiple responses from various districts within the state have the number of responses indicated in parentheses.

order to better characterize the range of volumes considered, the questionnaire asked respondents to provide their own values for low (less than or equal to . . .), medium (a range), and high (greater than or equal to . . .) traffic volumes for both rural and urban roadways. In order to make further dis- tinctions concerning treatment use on high-traffic-volume roadways, the agency-defined criteria for high traffic volume were exclusively examined. These criteria were grouped into one of three categories for both rural and urban roadways— “low” (ADT < 10,000 vpd), “medium” (ADT = 10,000 to 19,999 vpd), and “high” (ADT ≥ 20,000 vpd). A summary of the high-traffic-volume criteria grouped according to these three categories is provided in Table 2.7. The high-traffic-volume criteria reported by agencies were initially analyzed for trends concerning the use of the preser- vation treatments. Some key findings from this initial analysis are summarized in Tables 2.8 and 2.9, respectively. Each table lists the most-used treatments on HMA- and PCC-surfaced roadways, based on the three categories of high-traffic-volume criteria. In addition to the information included in Tables 2.8 and 2.9, the following specific details were noted from the responses regarding high-volume traffic: • Those agencies falling in the “high” criteria category reported not using the following treatments: cape seal, scrub seal, 20 Table 2.7. Responding Agencies’ High-Traffic-Volume Criteria and Criteria Categories High-Traffic-Volume Criteria Categories Low Criterion (ADT < 10,000 vpd) Medium Criterion (ADT = 10,000 to 19,999 vpd) High Criterion (ADT >– 20,000 vpd) Louisiana DOT (7,000) Alaska DOT (10,000) Connecticut DOT (30,000) Michigan DOT (3,400 est.) Hawaii DOT (10,000) Rhode Island DOT (30,000) Missouri DOT (1,000) Maine DOT (10,000) South Carolina DOT (20,000) Montana DOT (6,000) Minnesota DOT (10,000) British Columbia (100,000) New York DOT (4,000/lane) New Hampshire (10,000) Pennsylvania DOT (2,000) Oklahoma DOT (10,000) South Dakota DOT (1,500) Ontario (10,000) Washington DOT (5,000) Alberta (5,000) FHWA-CFLHD (4,000) For agencies that make a distinction between rural and urban traffic volume categorizations: Georgia DOT (5,000 rural/8,000 urban) Wyoming DOT (10,000 rural/15,000 urban) Virginia DOT (20,000 rural/40,000 urban) Iowa DOT (3,500 rural) Iowa DOT (11,500 urban) Florida DOT (10,000 rural) Florida DOT (40,000 urban) Kansas DOT (3,000 rural) Kansas DOT (20,000 urban) Kentucky DOT (5,000 rural) Kentucky DOT (10,000 urban) Mississippi DOT, Newton (3,000–7,000 rural) Mississippi DOT, Newton (20,000 urban) Mississippi DOT, Batesville (2,000 rural) Mississippi DOT, Batesville (10,000 urban) Mississippi DOT, Tupelo (3,000–7,000 rural) Mississippi DOT, Tupelo (20,000 urban) Nevada DOT (10,000 rural) Nevada DOT (100,000 urban) New Mexico DOT (5,000 rural) New Mexico DOT (15,000 urban) North Carolina DOT (5,000 rural) North Carolina DOT (10,000 urban) Tennessee DOT (5,000 rural) Tennessee DOT (10,000 urban) Texas DOT (1,000 rural) Texas DOT (10,000 urban) Manitoba (4,000 rural) Manitoba (10,000 urban) Quebec (8,000 rural) Quebec (20,000 urban)

21 Table 2.8. Initial Analysis of Most-Used Preservation Treatments for HMA-Surfaced High-Volume Roadways Rural Urban Low Medium High Low Medium High ≥60% SHAs and provinces report using: Crack fill Crack seal Thin HMA overlay Drainage preservation ≥50% SHAs and provinces additionally report using: Single-course microsurfacing Thin bonded wearing course Cold mill and overlay Crack fill Crack seal Ultra-thin bonded wearing course Cold mill and overlay Drainage preservation Thin HMA overlay Profile milling Crack fill Crack seal Thin HMA overlay Drainage preservation Crack fill Crack seal Single-course microsurfacing Ultra-thin bonded wearing course Drainage preservation Crack fill Crack seal Multiple-course microsurfacing Cold mill and overlay Drainage preservation Thin bonded wearing course Crack fill Crack seal Drainage preservation Table 2.9. Initial Analysis of Most-Used Preservation Treatments for PCC-Surfaced High-Volume Roadways Rural Urban Low Medium High Low Medium High ≥80% DOTs and provinces report using: Joint reseal Diamond grinding Full-depth patching ≥70% DOTs and provinces additionally report using: Crack seal Partial-depth patching Diamond grinding Full-depth patching Dowel bar retrofit Crack seal Partial-depth patching Drainage preservation Joint reseal Crack seal Diamond grinding Full-depth patching At 67%: Partial-depth patching Thin HMA overlay Drainage preservation Joint reseal Crack seal Diamond grinding Partial-depth patching Full-depth patching Dowel bar retrofit Drainage preservation Joint reseal Crack seal Diamond grinding Full-depth patching At 64%: Partial-depth patching Dowel bar retrofit Drainage preservation Joint reseal Diamond grinding Full-depth patching Crack seal At 63%: Partial-depth patching At 50%: Dowel bar retrofit Drainage preservation single- and multiple-course chip seals, cold in-place recycling, and ultra-thin whitetopping. Nor did they report using any “other” specific treatments (Figures 2.2 and 2.3). • No agencies reported currently using scrub seal. • Two SHAs with “high” volume designations, Nevada and Utah, reported using fog seal. • As shown in Figures 2.2 and 2.3, for all agencies reporting traffic volume designations, crack fill and crack seal are used by at least 60% of reporting agencies. Additionally, on rural roads, thin HMA overlays and drainage preven- tion are used by at least 60% of agencies (see Figure 2.2), while on urban roads, drainage preservation is used by at

22 0 10 20 30 40 50 60 70 80 90 100 Cra ck Fil l Cra ck Se al Sin gle -Co urs e M icr os urf ac ing Mu ltic ou rs e Mi cro su rfa cin g Sin gle -Co urs e Ch ip S ea l Ch ip S ea l w ith Po lym er Th in Bo nd ed W ea rin g C ou rse Th in HM A O ver lay Co ld- Mil led HM A O ver lay Ult ra- Th in HM A O ver lay Ho t In -Pl ac e R ec ycl ing Co ld In- Pla ce Re cyc ling Pro file M illin g Ult ra- Th in Wh ite top pin g Dr ain ag e P res erv atio n Treatment % o f A ge n c ie s Low (<10,000) Medium (10,000–19,999) High (>20,000) Figure 2.2. Treatment use on rural HMA-surfaced roadways, by category of high-traffic-volume criteria. 0 10 20 30 40 50 60 70 80 90 100 Treatment % o f A ge n c ie s Low (<10,000) Medium (10,000–19,999) High (>20,000) Cra ck Fill Cra ck Se al Sin gle -Co urs e Mi cro su rfa cin g Mu ltic ou rse M icr os ur fac ing Sin gle -Co urs e C hip Se al Ch ip S ea l w ith Po lym er Th in Bo nd ed W ea rin g C ou rse Th in HM A O ver lay Co ld- Mi lled HM A O ver lay Ult ra- Th in HM A O ver lay Ho t In -Pl ac e Re cyc ling Co ld I n-P lac e R ecy clin g Pro file M illin g Ult ra- Th in Wh ite top pin g Dr ain ag e P re se rv ati on Figure 2.3. Treatment use on urban HMA-surfaced roadways, by category of high-traffic-volume criteria. least 60% (see Figure 2.3). Also shown in Figure 2.3, the com- bination treatment of cold milling and thin HMA overlay (<1.5 in.) is used on urban roads by at least 40% of report- ing agencies. • For PCC pavements (Figures 2.4 and 2.5), those agen- cies with “high” traffic volume designations reported not using thin PCC overlays on urban roads. Nor did they report using any “other” treatments on either rural or urban roads. • For all agencies reporting “high” traffic volume designations, joint seal, diamond grinding, and full-depth patching are used on PCC pavements by at least 80% of reporting agen-

cies (see Figures 2.4 and 2.5). Crack seal is used on rural PCC roads by 100% of reporting agencies (see Figure 2.4). With some differences noted between the treatment usage trends for low-, medium-, and high-traffic-volume criteria categories, an analysis was conducted to generate a numeric definition of high-traffic-volume ADT for rural and urban roadways. Using descriptive statistical analyses, histograms of ADT criterion levels for rural and urban roadways were created (see Figures 2.6 and 2.7) and then analyzed to identify the ADT level at which at least 50% of reporting agencies are represented. From this analysis, it was determined that high 23 0 10 20 30 40 50 60 70 80 90 100 Joint Resealing Crack Seal Diamond Grinding Partial-Depth Patching Full-Depth Patching Dowel Bar Retrofit Drainage Preservation Treatment % o f A ge n c ie s Low (<10,000) Medium (10,000–19,999) High (>20,000) Figure 2.4. Treatment use on rural PCC-surfaced roadways, by category of high-traffic-volume criteria. 0 10 20 30 40 50 60 70 80 90 100 Jo in t Re se al in g C ra ck S eal Di am ond Gr in di ng Partial-Depth Pa tc hi ng Full-Depth Pa tc hi ng Do we l Ba r Re tr of it Drai nage Pr es er va ti on Tr eat me nt % o f A g e n c i e s Low (<10,000) Medium (10,000–19,999) High (>20,000) Figure 2.5. Treatment use on urban PCC-surfaced roadways, by category of high-traffic-volume criteria.

traffic volume should be defined as an ADT of at least 5,000 and 10,000 vpd for rural and urban roadways, respectively. Modifications were then made to Table 2.7 to reflect the responding agencies whose high-traffic-volume criteria meet these new definitions. The results of this recategorization of agencies are shown in Table 2.10. However, it is recognized that this categorization is still somewhat arbitrary, as for some the high value may be low and for others the high may be too high. With the new high-volume traffic values serving as the basis for further treatment analysis, the evaluation of the “most used” treatments described previously was revisited. Table 2.11 and Figures 2.8 and 2.9 show the results of this analysis for HMA- surfaced roadways. Key findings from this analysis are summarized as follows: • As shown in Figures 2.8 and 2.9, crack fill and crack seal are used by at least 75% of reporting agencies. Additionally, on rural roads, drainage preservation and combined cold milling and thin HMA overlay are used by at least 70% and 60% of agencies, respectively (see Figure 2.8). On urban roads, drainage preservation and combined cold milling 24 0 2 4 6 8 10 12 14 0 t o 99 9 10 00 to 19 99 20 00 to 29 99 30 00 to 39 99 40 00 to 49 99 50 00 to 59 99 60 00 to 69 99 70 00 to 79 99 80 00 to 89 99 90 00 to 99 99 10 00 0 t o 10 99 9 11 00 0 t o 11 99 9 12 00 0 t o 12 99 9 13 00 0 t o 1 39 99 14 00 0 t o 14 99 9 15 00 0 t o 19 99 9 20 00 0 t o 29 99 9 30 00 0 t o 49 99 9 50 00 0 t o 99 99 9 10 00 00 + Rural ADT Levels N o . o f A ge n ci es 0.00% 10.00% 20.00% 30.00% 40.00% 50.00% 60.00% 70.00% 80.00% 90.00% 100.00% Figure 2.6. Histogram and cumulative percentage of high-traffic-volume ADT on rural roadways. 0 2 4 6 8 10 12 14 16 0 t o 99 9 10 00 to 19 99 20 00 to 29 99 30 00 to 39 99 40 00 to 49 99 50 00 to 59 99 60 00 to 69 99 70 00 to 79 99 80 00 to 89 99 90 00 to 99 99 10 00 0 t o 10 99 9 11 00 0 t o 11 99 9 12 00 0 t o 12 99 9 13 00 0 t o 13 99 9 14 00 0 t o 14 99 9 15 00 0 t o 19 99 9 20 00 0 t o 29 99 9 30 00 0 t o 49 99 9 50 00 0 t o 99 99 9 10 00 00 + Urban ADT Levels No . o f A ge n ci es 0.00% 10.00% 20.00% 30.00% 40.00% 50.00% 60.00% 70.00% 80.00% 90.00% 100.00% Figure 2.7. Histogram and cumulative percentage of high-traffic-volume ADT on urban roadways.

25 Table 2.10. Recategorization of Agencies Based on New Definitions of Rural and Urban High-Traffic-Volume Levels New High-Traffic-Volume Criteria Categories Rural (ADT >– 5,000 vpd) Urban (ADT >– 10,000 vpd) Louisiana DOT (7,000) Alaska DOT (10,000) Washington DOT (5,000) Connecticut DOT (30,000) Alberta (5,000) Hawaii DOT (10,000) Maine DOT (10,000) Minnesota DOT (10,000) New Hampshire (10,000) Oklahoma DOT (10,000) Rhode Island DOT (30,000) South Carolina DOT (20,000) British Columbia (100,000) Ontario (10,000) For agencies that make a distinction between rural and urban traffic volume categorizations: Georgia DOT (5,000 rural) Wyoming DOT (10,000 rural) Wyoming DOT (15,000 urban) Virginia DOT (20,000 rural) Virginia DOT (40,000 urban) Iowa DOT (11,500 urban) Florida DOT (10,000 rural) Florida DOT (40,000 urban) Kansas DOT (20,000 urban) Kentucky DOT (5,000 rural) Kentucky DOT (10,000 urban) Mississippi DOT, Newton (3,000–7,000 rural) Mississippi DOT, Newton (20,000 urban) Mississippi DOT, Batesville (10,000 urban) Mississippi DOT, Tupelo (3,000–7,000 rural) Mississippi DOT, Tupelo (20,000 urban) Nevada DOT (10,000 rural) Nevada DOT (100,000 urban) New Mexico DOT (5,000 rural) New Mexico DOT (15,000 urban) North Carolina DOT (5,000 rural) North Carolina DOT (10,000 urban) Tennessee DOT (5,000 rural) Tennessee DOT (10,000 urban) Texas DOT (10,000 urban) Manitoba (10,000 urban) Quebec (8,000 rural) Quebec (20,000 urban) Categorizations by agencies not included in trend analysis: Organizations: NAPA (10,000); NACE (15,000 rural/60,000 urban). Other: Colorado DOT categorizes by ESALs. Caltrans categorizes by traffic index (TI): TI ≤ 18 rural and TI ≤ 15 urban, where TI = 9.0 × (ESAL ÷ 106)0.119. Utah DOT (Region 4) categorizes by Interstate or non-Interstate (25,000 ADT and 2,500 ADT, respectively). City of Phoenix, Ariz., categorizes by 20,000 ADT rural, 50,000 ADT urban.

and thin HMA overlay are used by at least 60% and 70%, respectively (see Figure 2.9). Also shown in Figure 2.9, single- and multiple-course microsurfacing, ultra-thin bonded wearing course, and thin HMA overlays (<1.5 in. [<38 mm]) are used on urban roads by at least 40% of respondents. • Cape seal, scrub seal, and rejuvenator are not used by many reporting agencies. In addition, on urban roads, fog seals and multiple-course chip seals are not used by many agencies. Therefore, they are not included in Figures 2.8 and 2.9. • Only one agency, Nevada DOT, reported using scrub seal on rural or urban roadways with ADT ≥ 5,000 and ≥ 10,000 vpd, respectively. • A handful of agencies—Hawaii, Minnesota, Montana, and Alberta (Canada)—noted using “other” preservation treatments.  Hawaii reported only doing 1.5-in. (38-mm) HMA mill and fill as a preservation technique for rural and urban roadways.  Minnesota requires that all chip seal applications receive a fog seal.  Montana applies thin HMA overlays (< 2.375 in. [< 60 mm]) on rural roadways.  Alberta uses a combination of profile milling and thin overlay on rural roadways. Similar analyses were performed for treatments used on PCC pavements. The high-traffic-volume results were ana- lyzed for trends concerning treatment use, as well as treat- ment use in relation to pavement performance issues. The findings of this analysis are summarized in Table 2.12 and Figures 2.10 and 2.11. Key findings from the analysis of PCC treatments are summarized as follows: • As shown in Figures 2.10 and 2.11, for both rural and urban roadways, joint resealing, diamond grinding, and full-depth patching are used by at least 70% of agencies. • Fewer than 40% of reporting agencies use diamond grooving, thin PCC overlays, or ultra-thin bonded wearing courses on both rural and urban roads. • Dowel bar retrofitting and drainage preservation are used on urban roads by at least 50% of reporting agencies (see Figure 2.11). 26 Table 2.11. Revised Analysis of Most-Used Preservation Treatments for HMA-Surfaced High-Volume Roadways Commonly Used Preservation Treatments on HMA-Surfaced High-Volume Roadways Rural (ADT >– 5,000 vpd) Urban (ADT >– 10,000 vpd) ≥60% SHAs and provinces report using: Crack fill Crack fill Crack seal Crack seal Cold mill and thin HMA overlay Cold mill and thin HMA overlay Drainage preservation Drainage preservation ≥50% additionally report using: Thin HMA overlay 0 10 20 30 40 50 60 70 80 90 100 Treatment % o f A ge n c ie s Cr ac k F ill Cr ac k S ea l Sin gle -C ou rse M icr os urf ac ing Mu ltic ou rse M icr os urf ac ing Sin gle -C ou rs e Ch ip Se al Ch ip Se al wit h P oly me r Th in Bo nd ed W ea rin g C ou rse Th in HM A O ve rla y Co ld- Mi lled HM A O ve rla y Ult ra- Th in HM A O ve rla y Ho t In -P lac e R ec ycl ing Co ld In- Pla ce Re cyc ling Pr ofi le Mi llin g Ult ra- Th in Wh ite top pin g Dr ain ag e P res erv ati on Figure 2.8. Treatment use on rural HMA-surfaced roadways, based on revised definition of rural high traffic volume (ADT >– 5,000 vpd).

• Only the Maine DOT reported using an “other” treatment on PCC. Maine once applied an ultra-thin bonded wearing course on a PCC pavement, which has since been rubblized and paved with HMA. In general, 60% of agencies report using a different set of treatments for rural high-traffic-volume roadways than on rural low-traffic-volume roads, while a slightly lower margin of the majority reports using a different set of treatments for urban high-traffic-volume roadways from those for urban low-traffic-volume roadways. Of the treatments used on HMA-surfaced pavements, the majority (80%) of respondents indicated that chip seals are not considered applicable for rural or urban high-traffic- volume roadways. Common issues were related to loose rock damage, flushing, dust, bleeding, raveling, noise concerns, and short life expectancy. However, when asked to rank the top three treatments used, approximately 40% of agencies included chip seals within the top three treatments used on rural and urban high-traffic-volume roadways. Washington State, Wyoming, Alaska, Maine, Alberta (Canada), and British Columbia (Canada) report using chip seals on high-traffic- volume rural roadways; Nevada, North Carolina, and Rhode Island report using chip seals on both rural and urban high- traffic-volume roads. Minnesota and New Hampshire report using chip seals with polymer-modified binders on high- traffic-volume urban roads. The most common and successful treatments used on high-traffic-volume roadways appear to be thin HMA overlays, cold milling and thin HMA overlay, and micro- surfacing, with crack seal also being successful on high-traffic rural roadways. As shown in Table 2.13, the least popular treatments are fog seal, scrub seal, and slurry seal, with just over half of respondents indicating these treatments are not considered for use on high-traffic-volume rural and urban roadways. Of the treatments used on PCC pavements, the majority (approximately two-thirds) of respondents indicated ultra-thin 27 0 10 20 30 40 50 60 70 80 90 100 Treatment % o f A ge n c ie s Cr ac k F ill Cr ac k S ea l Sin gle -C ou rse M icr os urf ac ing Mu ltic ou rse M icr os urf ac ing Sin gle -C ou rse Ch ip Se al Ch ip Se al wit h P oly me r Th in Bo nd ed W ea rin g C ou rs e Th in HM A O ve rla y Co ld- Mi lled HM A O ve rla y Ult ra- Th in HM A O ve rla y Ho t In -P lac e R ec ycl ing Co ld In- Pla ce R ec ycl ing Pr ofi le Mi llin g Ult ra- Th in Wh ite top pin g Dr ain ag e P res erv ati on Figure 2.9. Treatment use on urban HMA-surfaced roadways, based on revised definition of urban high traffic volume (ADT >– 10,000 vpd). Table 2.12. Revised Analysis of Most-Used Preservation Treatments for PCC-Surfaced High-Volume Roadways Commonly Used Preservation Treatments on PCC High-Volume Roadways Rural (ADT >– 5,000 vpd) Urban (ADT >– 10,000 vpd) ≥70% SHAs and provinces report using: Joint reseal Joint reseal Diamond grinding Crack seal Full-depth patching Diamond grinding Full-depth patching ≥50% additionally report using: Crack seal Partial-depth patching Partial-depth patching Dowel bar retrofit Dowel bar retrofit Drainage preservation Drainage preservation

28 0 10 20 30 40 50 60 70 80 90 100 Joint Resealing Crack Seal Diamond Grinding Partial-Depth Patching Full-Depth Patching Dowel Bar Retrofit Drainage Preservation Treatment % o f A ge n c ie s Figure 2.10. Treatment use on rural PCC-surfaced roadways, based on revised definition of rural high traffic volume (ADT >– 5,000 vpd). 0 10 20 30 40 50 60 70 80 90 100 Joint Resealing Crack Seal Diamond Grinding Partial-Depth Patching Full-Depth Patching Dowel Bar Retrofit Drainage Preservation Treatment % o f A ge n ci es Figure 2.11. Treatment use on urban PCC-surfaced roadways, based on revised definition of urban high traffic volume (ADT >– 10,000 vpd). bonded wearing courses and thin overlays (either HMA or PCC) are not considered applicable for rural or urban (although by a lower margin) high-traffic-volume roadways, as shown in Table 2.14. For the most part, truck traffic does not influence treat- ment use by reporting agencies. At most, nearly one-third of respondents report being less likely to use single-course chip seal on roadways with high truck traffic, and just over a quarter of respondents would be more likely to apply load-transfer restoration to such roads. Based on responses, agencies appear to have well-established policies regarding treatment use. Nearly 90% of respondents indicated they are not considering using any other treatments other than those they currently employ. Of the few agencies considering alternate treatments, the majority do not have the funding necessary to pursue such options.

Performance Issues Addressed by Preservation Treatments The top three deficiencies addressed on rural HMA-surfaced pavements are light and moderate surface distress, raveling, and friction loss. On urban HMA-surfaced pavements, the top three deficiencies are light surface distress, raveling, and friction loss. Considering the most-used treatments for HMA-surfaced pavements, the primary issues targeted are related to surface deterioration. As shown in Figures 2.12 through 2.14, thin HMA overlays are applied to target a wider range of perfor- mance issues, including raveling, bleeding, and friction concerns. For PCC pavements, the top three pavement perfor- mance issues addressed are related to smoothness/ride quality and surface distress, with some concern about noise issues. The most-used preservation treatments appear to address specific issues without as much overlap between treatments; that is, joint resealing targets light to moderate surface dis- tresses (Figure 2.15), whereas full-depth patching targets moderate to high surface distresses (Figure 2.16), and diamond grinding targets smoothness, friction, and noise concerns (Figure 2.17). Work-Zone Requirements For most of the treatments listed, an overwhelming number of respondents reported using overnight or single-shift closures for application. Ultra-thin whitetopping on HMA-surfaced pavements and thin PCC overlays on PCC pavements are exceptions, requiring longer closure times. On urban PCC 29 Table 2.14. Summary of Preservation Treatments Considered Not Applicable for PCC Rural and Urban Roadways Treatments for Portland Cement Not Applicable % Checked Concrete (PCC) Pavements Rural/Urban Thin PCC overlays 62/55 Ultra-thin bonded wearing course 75/73 Thin HMA overlays 62/55 (<1.5 in. [<38 mm]) Table 2.13. Summary of Preservation Treatments Considered Not Applicable for HMA Rural and Urban Roadways Treatments for Hot-Mix Asphalt Not Applicable % Checked (HMA)–Surfaced Pavements Rural/Urban Fog seal 51/69 Scrub seal 54/72 Slurry seal 51/62 Single-course chip seal 83/91 Multiple-course chip seal 80/88 Chip seals with polymer-modified 71/84 asphalt binder Ultra-thin whitetopping 57/NA Ra ve lin g Ox ida tio n Ble ed ing Sm oo th/ Rid e Q ua lity Fri cti on No ise Lig ht Su rf D ist res s Mo d S urf Di str es s He av y S urf Di str es s 0% 20% 40% 60% 80% 100% % o f A ge n ci es Us in g Tr ea tm e n t Rural Urban Figure 2.12. Percentage of agencies filling cracks on rural and urban high-traffic-volume HMA-surfaced roadways to address pavement distresses.

30 Ra ve lin g Ox ida tio n Ble ed ing Sm oo th/ Rid e Q ua lity Fri cti on No ise Lig ht Su rf D ist res s Mo d S urf Di str es s He av y S urf Di str es s 0% 20% 40% 60% 80% 100% % o f A ge n ci es U si n g Tr ea tm en t Rural Urban Figure 2.13. Percentage of agencies sealing cracks on rural and urban high-traffic-volume HMA-surfaced roadways to address pavement distresses. 0% 20% 40% 60% 80% 100% % o f A ge n ci es U si n g Tr ea tm en t Rural Urban Ra ve lin g Ox ida tio n Ble ed ing Sm oo th/ Rid e Q ua lity Fri cti on No ise Lig ht Su rf D ist res s Mo d S urf Di str es s He av y S urf Di str es s Figure 2.14. Percentage of agencies applying thin HMA overlay on rural and urban high-traffic-volume HMA-surfaced roadways to address pavement distresses.

31 0% 20% 40% 60% 80% 100% % o f A ge n ci es Us in g Tr ea tm en t Rural Urban Ra ve lin g Ox ida tio n Ble ed ing Sm oo th/ Rid e Q ua lity Fri cti on No ise Lig ht Su rf D ist res s Mo d S urf Di str es s He av y S urf Di str es s Figure 2.15. Percentage of agencies resealing joints on rural and urban high-traffic-volume PCC roadways to address pavement distresses. 0% 20% 40% 60% 80% 100% % o f A ge n ci es Us in g Tr ea tm en t Rural Urban Ra ve lin g Ox ida tio n Ble ed ing Sm oo th/ Rid e Q ua lity Fri cti on No ise Lig ht Su rf D ist res s Mo d S urf Di str es s He av y S urf Di str es s Figure 2.16. Percentage of agencies using full-depth patching on rural and urban high-traffic-volume PCC roadways to address pavement distresses.

roadways, there is a distinct hierarchy amongst the scenarios, but the majority tends to use overnight or single-shift closures; noticeably fewer note using longer closures, except for thin PCC overlays. Contracting Mechanisms Between 30% and 50% of the respondents reported using contract maintenance for constructing preservation treatments on high-traffic-volume HMA- and PCC-surfaced roadways. Fewer than 25% reported using warranties for treatments applied to HMA-surface pavements, whereas less than 5% reported using warranties for treatments applied to PCC- surfaced pavements. Between 65% and 75% of the respondents indicated using method-based specifications (with some level of QC/QA) for ensuring the quality and performance of treatments applied to HMA-surfaced pavements, whereas between 50% and 75% used method-based specifications for treatments applied to PCC-surfaced pavements. Between 25% and 50% indicated using performance specifications to ensure the quality and performance of treatments applied to both surface types. The majority of those that do not currently practice QC/QA for pavement preservation indicated they do not plan to imple- ment such practices or to require warranties. Preservation Guidance Needs In general, the respondents did not report that guidance is needed for determining typical traffic control requirements or for closure-time information. However, some guidance was requested concerning the following: • Other agency experience; • Typical noise associated with treatment; • Treatment production rate; • Treatment costs by region; • Obtaining experienced contractors; • Material availability; and • Opening to traffic. The areas where the most guidance is needed include the following: • Durability and expected life of treatment; • Applicable traffic volume; and • Appropriate climatic conditions for treatment. Closing The survey of practice provided insight into agency practices regarding pavement preservation of high-traffic-volume roadways. Although most agencies use a variety of preserva- tion treatments on their respective networks, a more selective approach is required when considering such treatments for use on high-traffic-volume roadways. By analyzing treatment preference across the United States and Canada through this survey, the more commonly used treatments were identified, allowing the evaluation of best practices for a limited number of treatments. 32 0% 20% 40% 60% 80% 100% % o f A ge n ci es Us in g Tr ea tm en t Rural Urban Ra ve lin g Ox ida tio n Ble ed ing Sm oo th/ Rid e Q ua lity Fri cti on No ise Lig ht Su rf D ist res s Mo d S urf Di str es s He av y S urf Di str es s Figure 2.17. Percentage of agencies diamond grinding rural and urban high-traffic-volume PCC roadways to address pavement distresses.

Next: Chapter 3 - Development of Preservation Guidelines for High-Traffic-Volume Roadways »
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TRB’s second Strategic Highway Research Program (SHRP 2) Report S2-R26-RR-1: Preservation Approaches for High-Traffic-Volume Roadways documents the state of the practice of preservation treatment on asphalt and concrete pavements. The report focuses on treatments suitable for application on high-traffic-volume roadways but also discusses current practices for low-volume roadways.

The same project that produced SHRP 2 Report S2-R26-RR-1 also produced SHRP 2 Report S2-R26-RR-2: Guidelines for the Preservation of High-Traffic-Volume Roadways. The report provides suggested guidelines for the application of preservation treatments on high-traffic-volume roadways and considers traffic volume, pavement condition, work-zone requirements, environmental conditions, and expected performance.

An e-book version of this report is available for purchase at Google, iTunes, and Amazon.

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