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

Chapter: Chapter 2 - Factors Affecting Project and Treatment Selections for Pavement Preservation

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Suggested Citation:"Chapter 2 - Factors Affecting Project and Treatment Selections for Pavement Preservation." National Academies of Sciences, Engineering, and Medicine. 2011. Guidelines for the Preservation of High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14487.
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Suggested Citation:"Chapter 2 - Factors Affecting Project and Treatment Selections for Pavement Preservation." National Academies of Sciences, Engineering, and Medicine. 2011. Guidelines for the Preservation of High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14487.
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Suggested Citation:"Chapter 2 - Factors Affecting Project and Treatment Selections for Pavement Preservation." National Academies of Sciences, Engineering, and Medicine. 2011. Guidelines for the Preservation of High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14487.
×
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Suggested Citation:"Chapter 2 - Factors Affecting Project and Treatment Selections for Pavement Preservation." National Academies of Sciences, Engineering, and Medicine. 2011. Guidelines for the Preservation of High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14487.
×
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Suggested Citation:"Chapter 2 - Factors Affecting Project and Treatment Selections for Pavement Preservation." National Academies of Sciences, Engineering, and Medicine. 2011. Guidelines for the Preservation of High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14487.
×
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Suggested Citation:"Chapter 2 - Factors Affecting Project and Treatment Selections for Pavement Preservation." National Academies of Sciences, Engineering, and Medicine. 2011. Guidelines for the Preservation of High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14487.
×
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Suggested Citation:"Chapter 2 - Factors Affecting Project and Treatment Selections for Pavement Preservation." National Academies of Sciences, Engineering, and Medicine. 2011. Guidelines for the Preservation of High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14487.
×
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Suggested Citation:"Chapter 2 - Factors Affecting Project and Treatment Selections for Pavement Preservation." National Academies of Sciences, Engineering, and Medicine. 2011. Guidelines for the Preservation of High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14487.
×
Page 11
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Suggested Citation:"Chapter 2 - Factors Affecting Project and Treatment Selections for Pavement Preservation." National Academies of Sciences, Engineering, and Medicine. 2011. Guidelines for the Preservation of High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14487.
×
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Suggested Citation:"Chapter 2 - Factors Affecting Project and Treatment Selections for Pavement Preservation." National Academies of Sciences, Engineering, and Medicine. 2011. Guidelines for the Preservation of High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14487.
×
Page 13
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Suggested Citation:"Chapter 2 - Factors Affecting Project and Treatment Selections for Pavement Preservation." National Academies of Sciences, Engineering, and Medicine. 2011. Guidelines for the Preservation of High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14487.
×
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C H A P T E R 2 Factors Affecting Project and Treatment Selections for Pavement PreservationThere are many factors that affect the selection of a pavement- preservation project and treatment. For high-traffic-volume roadways in particular, the ability of the treatment to stand up to higher traffic volumes is certainly important. Other factors also increase in importance as the desire to minimize owner risk and disruption to the traveling public are considered. These guidelines identify the following factors, which are described in greater detail in the sections that follow: • Traffic levels; • Pavement condition; • Climate/environment; • Work zone duration restrictions; • Expected treatment performance; and • Costs. Traffic Level The traffic level is important for at least two reasons: it is a direct measure of the loadings applied to a roadway and it affects access to a roadway to perform preservation activities. Traffic levels may also be indirectly related to an agency’s risk tolerance: the higher the ADT, the less likely the agency is to try a treatment that may not have a long life or, if it fails, may adversely affect many users. One of the steps taken in developing these guidelines was to arrive at a definition of “high”-traffic-volume roadways. There is no national or American Association of State High- way and Transportation Officials (AASHTO) definition of high traffic volumes, probably because it is a local issue: what one agency defines as high traffic volume could easily be considered low traffic volume by another. To address this variability, a survey of state highway agencies’ (SHA) prac- tices was conducted in which agencies were asked how they defined low, medium, and high traffic on both rural and urban roadways. The responses were broken down using descriptive statistical analyses to plot histograms of ADT4levels for rural and urban roadways. These plots were analyzed to determine at what ADT at least 50% of reporting agencies were represented. As a result of the responses and the analy- ses, it was determined that a reasonable definition of high traffic volume is 5,000 vpd for rural roadways and 10,000 vpd for urban roadways. This is described in greater detail in the project report. The high-traffic-volume classification levels provided by the responding highway agencies were also analyzed for trends concerning preservation treatment use. According to survey responses, crack sealing, followed by crack filling, cold milling, and thin HMA overlays, are the treatments most extensively used on both rural and urban HMA-surfaced roadways. Sim- ilarly, joint resealing, crack sealing, and diamond grinding are the treatments with the greatest use on rural and urban PCC pavements. At the opposite end, preservation treatments such as cape sealing, fog sealing, and diamond grooving are used infrequently on high-traffic-volume roads. Tables 2.1 and 2.2 summarize the use of preservation treatments on HMA- and PCC-surfaced roadways, respectively. From this, the general practice of each treatment can be assessed accord- ing to the traffic level of the roadway. In addition to determining the extent of treatment use, information was sought on which treatments are predomi- nantly used on high-traffic-volume roadways and whether there is a difference in strategies for treating rural roadways as opposed to urban roadways. Overall, approximately 60% of agencies reported using a different set of treatments for rural high-traffic-volume roadways versus rural low-traffic- volume roadways, whereas a slightly lower margin of the majority reported using a different set of treatments for urban high-traffic-volume roadways versus urban low-traffic- volume roadways. However, there was little difference in treat- ment strategies between rural and urban high-traffic-volume roadways. Tables 2.3 and 2.4 list the preservation treatments used by at least 50% of highway agencies on their rural and urban high-traffic-volume roadways.

5Treatment Usage Rural Urban Treatment (ADT >5,000 vpd) (ADT >10,000 vpd) Crack filling Extensive Extensive Crack sealing Extensive Extensive Slurry seal Limited Limited Microsurfacing Moderate Moderate Chip seals Moderate Moderate Ultra-thin bonded Moderate Moderate wearing course Thin HMA overlay Extensive Extensive Cold milling and Extensive Extensive overlay Ultra-thin HMA overlay Limited Moderate Hot in-place HMA Limited Limited recycling Cold in-place recycling Moderate Moderate Profile milling Moderate Moderate Ultra-thin whitetopping Limited Limited Note: Extensive = Use by ≥66% of respondents; Moderate = 33% to 66% usage; Limited = <33% usage. Table 2.1. Preservation Treatment Use on High-Traffic-Volume Rural and Urban HMA-Surfaced RoadwaysAn important element of the overall traffic level is the aver- age daily truck traffic (ADTT) or the percentage of the ADT that is made up of trucks. However, agencies did not report that truck traffic has a significant influence on preservation treatment selection. Pavement Condition In selecting the right preservation treatment for a pavement, the condition of the existing pavement is important. Not only is the overall condition important, but the specific distresses present on the pavement also impact the selection of the proper preservation treatment. It is rare to encounter a single pave- ment condition, so these guidelines have been structured such that the suitability of various treatments for combinations of pavement conditions has been considered, where possible. Although it is always important to apply preservation treat- ments at the right time to address the right condition(s), this is especially applicable to high-traffic-volume roadways. For example, if two roads of the same design are constructed to the same standards under the same environmental conditions, it is expected that these roadways would perform identicallyTreatment Usage Rural Urban Treatment (ADT >5,000 vpd) (ADT >10,000 vpd) Concrete joint sealing Extensive Extensive Concrete crack sealing Extensive Extensive Diamond grinding Extensive Extensive Diamond grooving Moderate Extensive Partial-depth concrete Extensive Moderate patching Full-depth concrete Extensive Extensive patching Dowel bar retrofitting Moderate Moderate (i.e., load transfer restoration) Ultra-thin bonded Limited Moderate wearing course Thin HMA overlay Limited Moderate Note: Extensive = Use by ≥66% of respondents; Moderate = 33% to 66% usage; Limited = <33% usage. Table 2.2. Preservation Treatment Use on High-Traffic-Volume Rural and Urban PCC-Surfaced RoadwaysRoadway Category Rural (ADT >5,000 vpd) Urban (ADT >10,000 vpd) Crack fill Crack fill Crack seal Crack seal Thin HMA overlay Cold mill and overlay Cold mill and overlay Drainage preservation Drainage preservation Table 2.3. Preservation Treatments Commonly Used on High-Traffic-Volume HMA-Surfaced RoadwaysRoadway Category Rural (ADT >5,000 vpd) Urban (ADT >10,000 vpd) Joint seal Joint seal Crack seal Crack seal Diamond grinding Diamond grinding Full-depth patching Full-depth patching Partial-depth patching Partial-depth patching Dowel bar retrofitting Dowel bar retrofitting Drainage preservation Table 2.4. Preservation Treatments Commonly Used on High-Traffic-Volume PCC-Surfaced Roadways

6under the same traffic conditions. However, when increased traffic loadings are applied, the pavement with the greater load will deteriorate faster. This can be illustrated with perfor- mance curves showing that the time for treatment application is reduced for pavements with higher traffic volumes. While the correct treatment application time depends on several factors, it is generally agreed that preservation treat- ments should be applied during the period when the pavement is in good condition. Accordingly, surveying existing condi- tions to determine whether the pavement is in good condition is an important part of the treatment selection process. The selection of the correct type of preservation for dis- tressed pavements generally depends on the location, density, and magnitude of the distress. For instance, where a surface treatment cannot be applied to a PCC pavement, such as a heavily trafficked urban roadway, diamond grinding is often performed to improve rideability. Resealing of joints in PCC pavements is done wherever poor sealing or lack of sealing is evident. On HMA-surfaced roadways, if transverse cracking is frequent but there is not a high degree of edge deteriora- tion, a surface treatment such as a chip seal or slurry seal may be the best preservation strategy. If the transverse cracks are low to moderate in frequency and have progressed to a point of high edge deterioration, then crack repair or patching may be necessary. If cracks are moderate in density and have little deterioration, effective treatment can be accomplished by crack sealing or filling. Extensive longitudinal cracking in the wheel path is indicative of a structural problem, which makes the pavement a poor candidate for preservation treatment. While crack sealing is primarily performed on newer pave- ments with fairly narrow cracks, crack filling is most often reserved for more worn, older pavements with wider, more randomly occurring cracks. Thin HMA overlays can be used on all types of roadways in good to fair condition for functional improvements. Such over- lays are particularly suitable for high-traffic-volume roadways in urban areas, where longer life and relatively low-noise sur- faces are desired. Similarly, slurry seals do not usually perform well if the underlying pavement contains extensive cracks (Morian et al. 1998). Tables 2.5 and 2.6 reflect the state of the practice for treat- ment use by transportation agencies based on existing pave- ment surface conditions. In these tables, extensive use means that two-thirds or more of the highway agencies reported using a particular treatment to address a certain pavement deficiency. Moderate use represents use by between one-third and two-thirds of the agencies, while limited use represents use by less than one-third of the agencies. The results pre- sented in these tables were combined with the application best practices information contained in the literature to for- mulate a decision matrix for identifying feasible treatments based on existing pavement condition. The decision matrix isa key part of the treatment selection framework/process pre- sented later in this document. Climate/Environment Climatic conditions impact preservation treatment usage in at least two ways: determining construction timing and affect- ing treatment performance. While the applicability of many of the treatments might not be affected by differences in cli- mate (such as ultra-thin friction courses for HMA-surfaced pavements or diamond grinding for PCC pavements), some treatments, especially those using asphalt emulsions, can only be applied in limited temperature and humidity conditions. Climate can directly affect curing time, which in turn impacts treatment feasibility and opening to traffic on high-volume roadways. For example, slurry seals require several hours, warmer temperatures, and direct sunlight to break and cure effectively; in environments where these conditions cannot be assured and traffic cannot be kept off the pavement, a slurry seal is not an appropriate treatment. In addition to temperature and climate considerations during treatment placement, preservation treatments can experience differential performance in different climates. For example, although thin HMA overlays are used successfully in all climatic regions, they are susceptible to thermal crack- ing, which can be more pronounced in colder climates. The performance of ultra-thin HMA overlays is particularly lim- ited in cold climates because of the thermal cracking issue and the challenges in achieving adequate density on thin lifts. Cold-applied (emulsion-based) treatments must be placed during the day and in warm temperatures, while treatments constructed with hot asphalt binder 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 per- formance of chip seals is related both to favorable climatic conditions during placement and also to favorable climatic conditions during the weeks following placement. A major cause of pavement failure is weather-related, such as when rain or extreme temperatures occur shortly after construction (Croteau et al. 2005). Some thin surfacings are also more susceptible to damage from certain types of snow plowing techniques and certain plow blades. From agency-provided responses on preservation prac- tices, information was obtained that permitted the catego- rization of practices according to climate region, which in turn could be evaluated to determine whether their treatment use was at least partially driven by climatic factors. For the three climatic regions identified—deep-freeze (northern-tier states, freezing index [FI] >400), moderate-freeze (middle- tier states, 50 < FI ≤ 400), and no-freeze (southern-tier states and portions of coastlines, FI ≤50)—the general practice for

ent Distress Surface Distressa Treatment riction Noise Light Moderate Heavy Crack filling /A Limited Extensive Moderate Limited Crack sealing /A Limited Extensive Moderate Limited Slurry seal imited None Moderate Limited None Microsurfacing oderate Limited Extensive Moderate Limited Chip seals oderate None Extensive Extensive Limited Ultra-thin bonded we xtensive Limited Extensive Moderate Limited Thin HMA overlay oderate Limited Extensive Extensive Limited Cold milling and ove oderate Limited Extensive Extensive Moderate Ultra-thin HMA overl oderate Limited Extensive Moderate Limited Hot in-place HMA re oderate Limited Extensive Moderate Moderate Cold in-place recycli imited Limited Moderate Extensive Extensive Profile milling oderate Limited Moderate Limited None Ultra-thin whitetoppi imited Limited Moderate Moderate Limited Note: Extensive = Use by a Various forms of crackin Table 2.5. Treatm nditionPavem Raveling Oxidation Bleeding Smoothness F N/A N/A N/A Limited N N/A N/A N/A Limited N Extensive Extensive Limited Limited L Moderate Moderate Limited Moderate M Moderate Extensive Limited Limited M aring course Moderate Moderate Limited Moderate E Extensive Moderate Moderate Extensive M rlay Extensive Moderate Moderate Extensive M ay Moderate Moderate Moderate Moderate M cycling Moderate Moderate Limited Moderate M ng Limited Limited Limited Moderate L None None Limited Extensive M ng Limited Limited Limited Moderate L ≥66% of respondents; Moderate = 33% to 66% usage; Limited = <33% usage. g. ent Usage on HMA-Surfaced Roadways According to Pavement Co

8Pavement Distress Surface Distressa Treatment Smoothness Friction Noise Light Moderate Heavy Concrete joint resealing Limited None Limited Extensive Moderate Limited Concrete crack sealing Limited None Limited Extensive Moderate Limited Diamond grinding Extensive Moderate Moderate Limited Limited Limited Diamond grooving Moderate Extensive Limited Limited Limited Limited Partial-depth concrete patching Moderate None Limited Moderate Extensive Moderate Full-depth concrete patching Moderate Limited Limited Limited Extensive Extensive Dowel bar retrofitting Moderate Limited Limited Limited Moderate Moderate Ultra-thin bonded wearing course Extensive Moderate Limited Moderate Moderate Limited Thin HMA overlay Moderate Moderate Limited Moderate Moderate Limited Note: Extensive = Use by ≥66% of respondents; Moderate = 33% to 66% usage; Limited = <33% usage. a Spalling, various forms of cracking. Table 2.6. Treatment Usage on PCC-Surfaced Roadways According to Pavement Conditionusing each treatment was summarized, with the results shown in Tables 2.7 and 2.8. In these tables, extensive treatment use in a climate region is understood as at least two-thirds of respondents in that region reporting using the treatment on high-traffic-volume roadways. Moderate use is defined as between one-third and two-thirds of respondents using the treatment. Limited use is defined as less than one-third of respondents reporting using that treatment. Although there is variability among the climate regions regarding treatment usage, for the most part there is not a sig- nificant difference between treatment use on rural versus urban high-traffic-volume roadways within a climate region. Two treatments, slurry seal on HMA-surfaced pavements andthin PCC overlays on PCC pavements, were reportedly not used on either rural or urban high-traffic-volume roadways in deep-freeze environments. In other cases, such as use of ultra-thin whitetopping, limited use may be more likely attrib- uted to high cost or lack of local experience, rather than climate- related performance issues. Work Zone Duration Restrictions The time available to apply a treatment is a practical consid- eration in treatment selection on high-traffic-volume road- ways, as it dictates how much time is available to do the work.Climatic Crack Crack Slurry Single Multiple Single Multiple With Region Fill Seal Seal Course Course Course Course Polymer RURAL Deep freeze Extensive Extensive None Moderate Moderate Extensive Extensive Extensive Moderate freeze Extensive Extensive Moderate Extensive Moderate Moderate Limited Limited No freeze Moderate Moderate Limited Moderate Limited Moderate Moderate Moderate URBAN Deep freeze Extensive Extensive None Moderate Moderate Moderate Moderate Moderate Moderate freeze Extensive Extensive Moderate Extensive Extensive Moderate Limited Limited No freeze Extensive Extensive Moderate Moderate Limited Moderate Moderate Moderate Note: Extensive = Use by ≥66% of respondents; Moderate = 33% to 66% usage; Limited = <33% usage. Table 2.7. Preservation Treatment Use on High-Traffic-Volume HMA-Surfaced Roadways, by Climate Region Microsurfacing Chip Seal (continued on next page)

9One scheme for looking at available hours is to divide avail- able closure times into three groups: less than 12 hours, 12 to 60 hours, and more than 60 hours. These groups are approx- imately equivalent to an overnight closure, a closure between one-day and one-weekend long, and a closure that is longer than a weekend, respectively (Peshkin et al. 2006), although these ranges would vary based on local patterns of use, peak- hour rates, and so on. The survey feedback provided valuable information to identify facility closure times that State agencies typically use when performing preservation treatments associated with high-traffic-volume roadways (see Tables 2.9 and 2.10). Most preservation treatments on HMA-surfaced roads can be completed within a single shift or overnight closure. Specifi- cally for HMA pavements, the overnight closure time was the most frequently selected available scenario under which 12 of the 13 treatment alternatives are typically applied. The meth- ods most widely used with this length of closure include crack filling, crack sealing, slurry seals, microsurfacing, chip seals, ultra-thin bonded wearing courses, thin and ultra-thin HMA overlays, cold milling and overlay projects, and profile milling. It should be noted that most of these treatments are used under the same available work hour scenarios for both urban and rural areas. Hot in-place and cold in-place recycling are also used as single shift or overnight projects, but less frequently than the previously listed activities. Finally, ultra-thin whitetop- ping is more often performed as a weekend or extended closure project. Many pavement preservation techniques for PCC can be completed during an overnight or single-shift closure. The results indicated that all of the preservation treatments for urban PCC roads are considered for overnight or single-shift closures. When conventional patching materials are used forpartial- and full-depth repairs and for dowel bar retrofitting, longer closure times are required for the material to reach acceptable strength. On the other hand, use of high early strength PCC mixes and fast-track proprietary repair materi- als (and precast full-depth repair panels), usually enables these preservation treatments to be used in single-shift or overnight closures. Expected Treatment Performance Expected treatment performance also influences the selection of a preservation treatment. There may be higher expectations for treatment performance when there is more traffic because higher-traffic-volume roadways are expected to last longer. It is also harder to gain access to roads with higher traffic vol- umes, which contributes to the expectation that any work done on such roads should last longer. Also, as noted, there is a greater risk associated with a premature failure on such roads. The measure of expected treatment performance used in these guidelines is expected treatment life in years. To clarify, this does not refer to how long the treatment “lasts,” but rather to how long the treatment serves the purpose for which it was placed (i.e., provides a benefit). Since the purpose of preservation is to extend the life of a pavement, treatment performance must be measured in terms of the extension in service life imparted to the existing pavement by the treat- ment. This designation of performance is most compatible with the procedures needed to evaluate the cost-effectiveness of preservation treatments as part of a project-level treatment selection process. General ranges in the expected performance of treatments applied to HMA-surfaced pavements and PCC roadways areTable 2.7. (continued) Cold Ultra- Thin Thin Milling Thin Climatic Bonded HMA and HMA Profile Ultra-Thin Region Course Overlay Overlay Overlay Hot Cold Milling Whitetopping RURAL Deep freeze Moderate Extensive Extensive Limited Limited Moderate Limited Limited Moderate freeze Extensive Extensive Extensive Moderate Limited Moderate Moderate Limited No freeze Moderate Moderate Moderate None None Limited Moderate Limited URBAN Deep freeze Moderate Extensive Extensive Moderate Limited Moderate Limited Limited Moderate freeze Extensive Extensive Extensive Extensive Moderate Limited Extensive Moderate No freeze Moderate Moderate Extensive Limited Limited Moderate Moderate Limited In-Place Recycling

PCC Joint tial-Depth Full-Depth Dowel Bar Thin PCC Thin Bonded Thin HMA Climatic Region Sealing air Repair Retrofit Overlay Course Overlay RURAL Deep freeze Moderate nsive Extensive Extensive None Moderate Limited Moderate freeze Extensive nsive Extensive Moderate Limited Moderate Extensive No freeze Extensive nsive Extensive Moderate Limited Limited Limited URBAN Deep freeze Extensive erate Extensive Moderate None Limited Limited Moderate freeze Extensive nsive Extensive Moderate Limited Moderate Moderate No freeze Extensive nsive Extensive Extensive Limited Moderate Moderate Note: Extensive = Use by ≥66% of respo Table 2.8. Preservation Tre urfaced Roadways, by Climate RegionPCC Crack Diamond Diamond Par Sealing Grinding Grooving Rep Moderate Moderate Limited Exte Extensive Extensive Moderate Exte Extensive Extensive Limited Exte Moderate Moderate Limited Mod Extensive Extensive Moderate Exte Extensive Extensive Moderate Exte ndents; Moderate = 33% to 66% usage; Limited = <33% usage. atment Use on High-Traffic-Volume PCC-S

11Rural Urban Overnight or Overnight or Treatment Single Shift Weekend Longer Single Shift Weekend Longer Crack filling Extensive Limited Limited Extensive Limited Limited Crack sealing Extensive Limited Limited Extensive Limited Limited Slurry seal Extensive Limited Limited Extensive Limited Limited Microsurfacing Extensive Limited Limited Extensive Limited Limited Chip seal Extensive Limited Limited Extensive Limited Limited Ultra-thin bonded Extensive Limited Limited Extensive Limited Limited wearing course Thin HMA overlay Extensive Limited Limited Extensive Limited Limited Cold milling and overlay Extensive Limited Limited Extensive Limited Limited Ultra-thin HMA overlay Extensive Limited Limited Extensive Limited Limited Hot in-place HMA recycling Extensive Limited Limited Extensive Limited Limited Cold in-place recycling Extensive Limited Limited Extensive Limited Limited Profile milling Extensive Limited Limited Extensive Moderate Limited Ultra-thin whitetopping Moderate Limited Moderate Moderate Moderate Moderate Note: Extensive = Use by ≥66% of respondents; Moderate = 33% to 66% usage; Limited = <33% usage. Table 2.9. Survey Results from Treatments Used During Different Closure Durations for HMA-Surfaced PavementsRural Urban Overnight or Overnight or Treatment Single Shift Weekend Longer Single Shift Weekend Longer Concrete joint resealing Extensive Limited Limited Extensive Limited Limited Concrete crack sealing Extensive Limited Limited Extensive Limited Limited Diamond grinding Extensive Limited Limited Extensive Limited Limited Diamond grooving Extensive Limited Limited Extensive Limited Limited Partial-depth concrete patching Extensive Moderate Moderate Extensive Moderate Limited Full-depth concrete patching Extensive Moderate Moderate Moderate Moderate Moderate Dowel bar retrofitting Extensive Moderate Moderate Moderate Moderate Moderate Ultra-thin bonded wearing course Extensive Limited Limited Extensive Limited Limited Thin HMA overlay Extensive Limited Limited Extensive Limited Limited Note: Extensive = Use by ≥66% of respondents; Moderate = 33% to 66% usage; Limited = <33% usage. Table 2.10. Survey Results from Treatments Used During Different Closure Durations for PCC-Surfaced Pavements

12summarized in Tables 2.11 and 2.12, respectively. These ranges are based on information reported by various sources, repre- senting a variety of conditions, and using different perfor- mance measures. As such, these reported ranges may be based as much (or more) on perception instead of on well-designed, quantitative, experimental analyses. Additional evaluation of treatment performance was per- formed in this study, taking into consideration factors such as traffic volume, climatic/environmental conditions, and existing pavement conditions. This evaluation, which is doc- umented in the project report, resulted in refinements to some of the performance estimates listed above. The refined estimates are presented later in this document as part of the treatment selection process.Costs Although treatment costs do not affect treatment performance, certain cost considerations are inevitably a part of the treat- ment selection process. The cost of each treatment depends on features such as the size and location of the project, severity and quantity of distresses, and the quality of a treatment’s con- stituent materials. It also depends on the type and amount of surface preparation work and the degree of traffic control required to accompany the treatment. Allowing roads to deteriorate over time costs significantly more than maintaining roads in good condition. The cost for reconstruction of a 25-year-old roadway can be more than three times what it would have cost to “maintain” it using aExpected Performance Treatment Treatment Pavement Life Life (yr) Extension (yr) Crack filling 2–4 NA Crack sealing 3–8 2–5 Slurry seal 3–5 4–5 Microsurfacing Single course 3–6 3–5 Double course 4–7 4–6 Chip seal Single course 3–7 5–6 Double course 5–10 8–10 Ultra-thin bonded wearing course 7–12 NA Thin HMA overlay Dense graded 5–12 NA Open graded (OGFC) 6–12 NA Gap graded (SMA) NAa NA Cold milling and thin HMA overlay 5–12 NA Ultra-thin HMA overlay 4–8 NA Hot in-place recycling Surface recycle and thin HMA overlay 6–10b NA Remixing and thin HMA overlay 7–15c NA Repaving 6–15 NA Cold in-place recycling and thin HMA overlay Between 6–8 and 7–15d NA Profile milling 2–5 NA Ultra-thin whitetopping NA NA Sources: Peshkin et al. 1999; Lamptey et al. 2005; Peshkin and Hoerner 2005; Dunn and Cross 2001; Newcomb 2009; Cuelho et al. 2006; Okpala et al. 1999; Caltrans 2008; NDOR 2002. Note: NA = Not available. a Current indications are that SMA overlays perform the same or slightly better than dense-graded overlays. b Range based on reported performance of surface recycle and subsequent surface treatment. c Range based on reported performance of remixing and subsequent HMA overlay of unspecified thickness. d Range based on reported performance of CIR and subsequent surface treatment (6 to 8 years) and CIR and subsequent HMA overlay of unspecified thickness (7 to 15 years). Table 2.11. Expected Performance of Preservation Treatments Applied to HMA-Surfaced Pavements

13Table 2.12. Expected Performance of Preservation Treatments Applied to PCC-Surfaced Pavements Expected Performance Treatment Pavement Life Treatment Life (yr) Extension (yr) Concrete joint resealing 2–8 5–6 Concrete crack sealing 4–7 NA Diamond grinding 8–15 NA Diamond grooving 10–15 NA Partial-depth concrete patching 5–15 NA Full-depth concrete patching 5–15 NA Dowel bar retrofitting 10–15 NA Ultra-thin bonded wearing course 6–10 NA Thin HMA overlay 6–10 NA Sources: Peshkin et al. 1999; Smith et al. 2008; Peshkin et al. 2007; Caltrans 2008; NDOR 2002. Note: NA = Not available.sequence of preservation treatments over the same 25 years. Hence, cost is a critical component in the selection of appro- priate treatments at any traffic level. Tables 2.13 and 2.14 list the typical unit-cost ranges and corresponding relative costs of preservation treatments applied to HMA- and PCC-surfaced roadways, respectively. The costs represent the in-place costs of the treatments,exclusive of traffic control costs and any associated surface preparation costs. For HMA-surfaced roadways, the costs of crack sealing and filling are relatively low compared with other preservation techniques; however, the other preservation treatments can effectively address a broad range of conditions, so a direct comparison of costs is not appropriate. Reported cost esti- mates for slurry seals are approximately $0.75 to $1.00/yd2, depending on the size of the project, materials used, and the rate of application. Costs for microsurfacing vary consider- ably, but normally range between $1.50 and $3.00/yd2. While the cost of cold in-place recycling depends on numerous fac- tors, including depth of milling and the properties of the existing pavement, average costs are approximately $1.25 to $3.00/yd2. The cost of recycling can be four to six times more than the cost of chip seals and can be higher than the cost of constructing a thin HMA overlay. For PCC-surfaced roadways, the cost for full-depth repairs on jointed pavements varies significantly. Typical costs in the year 2000 ranged from $75 to $150/yd2. Diamond grinding costs were, on average, between $1.75 and $5.50/yd2. Costs fluctuate depending on many factors, including the existing pavement’s aggregate quality and PCC mix properties, average depth of removal, and smoothness requirements. SHAs have found that the cost of diamond grinding is generally lower than the cost of an HMA overlay, and such cost-effectiveness makes diamond grinding an appealing alternative for many concrete rehabilitation projects.Table 2.13. Estimated Treatment Costs for Preservation Treatments on HMA-Surfaced Pavements Treatment Relative Cost ($ to $$$$) Estimated Unit Cost Crack filling $ $0.10 to $1.20/ft Crack sealing $ $0.75 to $1.50/ft Slurry seal $$ $0.75 to $1.00/yd2 Microsurfacing (single-course) $$ $1.50 to $3.00/yd2 Chip seal (single-course) $$ (conventional) $1.50 to $2.00/yd2 (conventional) $$$ (polymer modified) $2.00 to $4.00/yd2 (polymer modified) Ultra-thin bonded wearing course $$$ $4.00 to $6.00/yd2 Thin HMA overlay (dense graded) $$$ $3.00 to $6.00/yd2 Cold milling and thin HMA overlay $$$ $5.00 to $10.00/yd2 Ultra-thin HMA overlay $$ $2.00 to $3.00/yd2 Hot in-place recycling (excluding thin HMA overlay for surface recycle and remixing types) $$/$$$ $2.00 to $7.00/yd2 Cold in-place recycling (excluding thin HMA overlay) $$ $1.25 to $3.00/yd2 Profile milling $ $0.35 to $0.75/yd2 Ultra-thin whitetopping $$$$ $15.00 to $25.00/yd2 Note: $ = low cost; $$ = moderate cost; $$$ = high cost; $$$$ = very high cost.

14Table 2.14. Estimated Treatment Costs for Preservation Treatments on PCC-Surfaced Pavements Relative Cost Treatment ($ to $$$$) Estimated Unit Cost Joint resealing $ Crack sealing $ Diamond grinding $$ Diamond grooving $$ Partial-depth patching $$/$$$ Full-depth patching $$/$$$ Dowel bar retrofitting $$$ Ultra-thin bonded $$$ wearing course Thin HMA overlay $$$ Note: $ = low cost; $$ = moderate cost; $$$ = high cost; $$$$ = very high cost. $1.00 to $2.50/ft $0.75 to $2.00/ft $1.75 to $5.50/yd2 $1.25 to $3.00/yd2 $75 to $150/yd2 (patched area) (equivalent $2.25 to $4.50/yd2, based on 3% surface area patched) $75 to $150/yd2 (patched area) (equivalent $2.25 to $4.50/yd2, based on 3% surface area patched) $25 to $35/bar (equiva- lent $3.75 to $5.25/yd2, based on 6 bars per 12-ft crack/joint and crack/joint retrofits every 30 ft) $4.00 to $6.00/yd2 $3.00 to $6.00/yd2Although these estimated costs depend on the condition of a particular roadway, as well as local contracting and con- struction costs and materials and techniques used, the direct cost of the treatment is often the easiest to determine. Gen- erally, this is available as historical cost data or estimated based on previous bids. In considering pavement condition, a pavement with more cracks will take more money per mile to seal or patch, and rougher pavements may take a higher quantity of emulsion for a chip seal. However, treatments such as milling and overlay or recycling are relatively inde- pendent of existing pavement condition, provided that the pavement is in sufficiently good shape to be a candidate for the treatment. The cost of eventual rehabilitation should account for how often the preservation process will be repeated and what needs to be performed. For example, a chip seal at the end of its life span can generally be covered with another chip seal. However, if the project was an overlay in an urban area with curb and gutter, milling might be necessary to maintain pro- file before another overlay can be added. Although less than a quarter of the survey respondents reported that they account for user costs when selecting a preservation treatment for high-traffic-volume roadways, these costs can represent a significant portion of the total cost and should be taken into account. Detailed guidance in computing certain forms of these costs is provided in Chapter 3.

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TRB’s second Strategic Highway Research Program (SHRP 2) Report S2-R26-RR-2: Guidelines for the Preservation of High-Traffic-Volume Roadways provides suggested guidelines for the application of preservation treatments on high-volume roadways. The guidelines consider traffic volume, pavement condition, work-zone requirements, environmental conditions, and expected performance.

Errata (October 2011): Table 3.2 (pp. 20-21) contained incorrect information in the following rows: chip seal (single); chip seal (double); and hot in-place recycling. The table has been corrected in the online version of the guide.

The same project that produced SHRP 2 Report S2-R26-RR-2 also produced SHRP 2 Report S2-R26-RR-1: Preservation Approaches for High-Traffic-Volume Roadways, which 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.

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