Maintenance and Surface Preparation Activities Prior to Pavement Preservation Treatments (2021)

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8 The results of the review of relevant publications are summarized in this chapter. A literature search identified available information on the links between (1) maintenance and surface prepa- ration and (2) pavement preservation. The literature search used key terms such as maintenance, surface preparation, and flexible and rigid pavements. The search also sought links between the maintenance and surface preparation activities and the preservation treatments, including information on triggering the need for the preparation activities, the timing of such activities, and the methods for tracking them. The search initially focused on publications produced after 2010 to avoid including now superseded or obsolete references, but in multiple instances, older works containing relevant content were included. Many of the resources cited in this chapter were not identified by a traditional literature search, instead coming from an Internet search employing the phrase “pavement preservation guidelines” coupled with the name of each state (i.e., 50 separate searches). The resulting docu- ments were then accessed from the relevant state DOT websites. Maintenance Treatments and Surface Preparation Practices The performance of many preservation treatments hinges on the condition of the pavement where those treatments are applied. If the pre-treatment condition of the pavement is not ideal, many agencies call for repairs, either specifically linking maintenance activities and preserva- tion treatments or generally stating that the pre-treatment condition may need to be addressed. The following sections summarize both types of practices. Flexible Pavement Maintenance and Surface Preparation Links between maintenance and specific preservation treatments sometimes emphasize the sequence and sometimes focus on ensuring the performance of the preservation treatment. For example, Testa and Hossain (2014) identify the following types of repairs that could be imple- mented prior to a chip seal: • Milling to correct high spots. • Leveling to fill depressions ranging from localized wheelpaths to longer depressions in multiple lanes. • Pothole repair. • Base repair. • Edge repair. • Crack sealing for fractures greater than ¼-inch wide. C H A P T E R   2 Literature Review

Literature Review 9   Texas chip seal guidelines also note repairs that are needed prior to placing a chip seal, specifi- cally indicating that cracks wider than 1/8 inch should be crack-sealed well ahead of seal coat placement (Texas DOT 2017). These guidelines are similar to Ohio recommendations for chip seals (which, at the time of publication in 2001, were viewed as low-volume road preventive maintenance). The Ohio DOT identifies the following conditions that call for repairs before a chip seal: wheelpath cracking, potholes, debonding, patches, cracks, longitudinal joint dete- rioration, and edge cracking (Ohio DOT 2001). It specifically states that cracking should be repaired prior to a chip seal to ensure its success. The Ohio Pavement Preventive Maintenance Guidelines also include recommendations for treatments other than chip seals (Ohio DOT 2001). For microsurfacing, advance repairs are needed for localized wheelpath cracking, potholes, debonding, and existing cracks, and patches should be in good repair. Similarly, for polymer-modified hot-mix asphalt (HMA) overlays, the Ohio DOT recommends prior repairs to localized wheelpath cracking, potholes, areas of debonding, existing patches (if needed), and cracks while cautioning against overband crack sealing. That same caution applies to thin HMA overlays with overband sealing done within 1 year of the overlay replacement and also suggests milling off high-severity raveling or bleeding and making repairs to wheelpath cracking, debonding, and longitudinal joint cracking. The New York State DOT provides guidance on pavement preparation for preventive main- tenance in Chapter 10 of its Comprehensive Pavement Design Manual (New York State DOT 2005), which addresses the following specified treatments and recommends the identified pre- treatment preparation: • Chip seal: crack sealing, removal of epoxy, polyester, thermoplastic and preformed markings, pavement cleaning. • Slurry seal: crack sealing (at least 3 months prior), rut filling, removal of thermoplastic and preformed markings, clean pavement surface. • Microsurfacing: crack sealing, removal of thermoplastic and preformed markings, clean pavement. • Paver-placed surface treatment: crack sealing, removal of thermoplastic and preformed markings, clean pavement (similar preparation is identified for thin overlays and 6.3 mm polymer-modified HMA overlays, which also require rut filling). The New Mexico Pavement Maintenance Manual (New Mexico DOT n.d.) offers similar advice for several of its treatments. For fog seals, it notes that “any existing distress that required to be repaired should have been done so.” In a chip seal construction checklist, it suggests checking that all pavement distresses have been repaired. For scrub seals and microsurfacing, the guidance is to “set up patching and crack repairs to take care of problem areas.” The Tennessee DOT Pavement Resurfacing Program Standard Operating Guidelines (Tennessee DOT 2018) cover the topic of surface preparation for several treatments commonly considered as pavement preservation. Their recommendations are summarized in Table 1. Connecticut approaches this topic of pre-preservation maintenance and surface preparation by using terminology that differs from that of other agencies (Connecticut DOT 2011). A draft document, which was published in 2011 but never implemented by the Connecticut DOT, iden- tifies effective treatments to address the observed deterioration displayed in two matrices. The observation is made that two treatments (a preparation treatment and a main treatment) can be combined to obtain desired results. The Connecticut combination often includes a crack treat- ment from Table 2 and a preservation treatment from Table 3 to address other surface condi- tions (Connecticut DOT 2011).

10 Maintenance and Surface Preparation Activities Prior to Pavement Preservation Treatments Treatment Recommended Existing Surface Preparation Crack sealing Clean or rout cracks. Fog seal Repair and patch all major defects; fill all cracks, other than hairline, with suitable bituminous crack filler. Slurry seal Pre-treat cracks with an acceptable crack sealer. Microsurfacing Repair any fatigue cracking or significant linear cracking. Thin asphalt overlay Repair minor base failures and depressions, fill surface voids, and remove any patched area with poor adhesion or a very high asphalt content that may bleed through the new surface. Source: Tennessee DOT (2018). Table 1. Pre-treatment maintenance activities for selected Tennessee preservation treatments. Distress Severity Crack Seal Crack Fill Thermal Cracking L E N M E N H X X Block Cracking L E E M E E H X X Longitudinal Paving Joint L E E M N E H1 X N Non-Wheelpath Cracking L E E M E M H X X Fatigue Cracking L M N M M N H N N Edge Cracking L M N M M N H N N Transverse Joint Reflection Cracking L E N M E N H X X Longitudinal Joint Reflection Cracking L M E M N E H N N Source: Connecticut DOT (2011). 1 High-severity paving joint can be locally repaired (20" min. mill and patch centered around joint, then considered as a Low Severity condition) or milled-and-filled joint and mat. E = effective M = marginally effective N = not effective X = counterproductive/not recommended Table 2. Applicability of crack treatments for various crack-related distresses.

Literature Review 11   Connecticut DOT’s draft guidance also introduces the concept of “ancillary treatments” that are to correct “secondary distress forms that are present but are not driving the deterioration of the pavement, or for isolated distress conditions for which the primary treatment does not provide relief (such as spot base failures, for instance, or pushing or shoving at a particular inter- section).” The following ancillary treatments are identified as candidates for specified distresses: crack sealing, crack filling, surface patches, partial-depth patching and full-depth patching (for composite pavements), micromilling, milling, and leveling. Distress Severity Rubberized Chip Seal 2-Lift Micro Ultra- Thin Overlay Thin Overlay Functional Overlay Mill and Fill Polishing L, M, H E E E E E E Bleed/Flush L E E E E E EM, H M E E E E E Thermal Cracking L M N N M M M M M N N N N M H X X X X X N Raveling L E E E E E E M M M M E E E H X X X M M E Surface Potholes L, M N N N N N EH X X X X X E Block Cracking L E E E E E E M E M M M E E H N N N N M E Longitudinal Paving Joint L E E E E E E M M E M E E E H1 X X X X N E Non-Wheelpath Cracking L M M M M M E M M N N N M E H X X X X X M Fatigue Cracking L N N N N M M M X X X X X X H X X X X X X Edge Cracking L M N N M M M M N N N N M M H N N N N N N Mix Rutting L X E X M M E M X M X X X E H X X X X X E Stabilized Rutting L X E N M E E M X E X N M E H X E X X X E Base Rutting All X X X X X X Transverse Joint Reflection Cracking L N N N N M E M X X X X N M H X X X X X X Longitudinal Joint Reflection Cracking L M N N M M E M N N N N N M H N N N N N M Depressions L N N N N M MM, H X X X X X X Source: Connecticut DOT (2011). E = effective M = marginally effective N = not effective X = counterproductive/not recommended 1 High-severity paving joint can be locally repaired (20" min. mill and patch centered around joint, then considered as a Low Severity condition) or milled-and-filled joint and mat. Table 3. Decision matrix for functional treatments for pavement preservation.

12 Maintenance and Surface Preparation Activities Prior to Pavement Preservation Treatments The Indiana DOT preservation guidelines include the observation that “the type and severity of distresses on existing pavement are major factors in selecting a treatment” (Lee and Shields 2010). The guidelines consider microsurfacing specifically, stating that “severely deteriorated surface should be repaired prior to the microsurfacing application using HMA patching and crack sealing . . . otherwise deterioration may be reflected on the microsurfacing.” The effect of existing pavement conditions on overlay performance is widely recognized, and this effect can be especially pronounced on the thinner overlays favored for pavement preservation. The asphalt pavement industry publication on thin asphalt overlays (<1.5 inches) for pavement preservation focuses primarily on milling as a surface preparation method, as shown in Table 4. NCHRP Synthesis 388 provides greater detail on general surface preparation practices prior to the construction of thicker overlays for both flexible and rigid pavements (Tenison and Hanson 2009). As exemplified in Table 5, other agencies address the relationship between maintenance and pavement preservation in general terms rather than linking a specific maintenance activity and a specific pavement preservation treatment. Rigid Pavement Maintenance and Surface Preparation The body of literature on links between maintenance and pavement preservation is much smaller for rigid pavements than for flexible pavements. This level of attention could reflect the total number of miles of flexible pavements versus rigid pavements or could indicate that pres- ervation is more commonly applied to flexible pavements. The concrete industry recommends a sequence of pavement repair procedures that includes treatments associated with pavement preservation but also considered by some to be mainte- nance. This sequence is illustrated in Figure 1, with treatments starting with partial-depth repairs and concluding with joint and crack resealing. The South Dakota DOT recommends a similar sequence, observing that “for rigid pave- ments, an appropriate treatment sequence consists of the following: full- or partial-depth repairs, load-transfer restoration, diamond grinding, and joint resealing” (South Dakota DOT 2010). The New Mexico DOT also discusses a sequence of pavement activities. Specifically for diamond grinding, it notes that “the road may have localized failures that should be corrected by crack treatments, partial-depth repairs, full-depth repairs, dowel bar retrofitting, etc.” (New Mexico DOT n.d.). Distress Recommended Investigation Extent Surface Preparation Prior to Overlay Raveling Visual observation Up to 100% of pavement area Clean and tack Longitudinal Cracking (non-wheelpath) Visual observation Coring Crack depth confined to surface layer Mill to crack depth, clean, and tack Longitudinal Cracking (wheelpath) Visual observation Coring Crack depth confined to surface layer Mill to crack depth, clean, and tack Transverse Cracking Visual observationCoring Crack depth confined to upper layers Mill surface, clean, fill exposed cracks, and tack Fatigue Cracking Visual observationCoring Crack depth confined to surface layer Mill to crack depth, clean, and tack Rutting or Shoving Visual observation Transverse trench or coring Rutting confined to surface layer Mill to depth of surface layer, clean, and tack Source: Based on Newcomb (2009). Table 4. Suggested approaches to surface preparation before thin overlays based on distresses.

Literature Review 13   The National Concrete Pavement Technology Center published an extensive guide to con- crete pavement preservation (Smith et al. 2014) covering the following treatments: slab stabiliza- tion and slab jacking, partial-depth repairs, full-depth repairs, retrofitted edgedrains, dowel bar retrofit, cross stitching, slot stitching, diamond grinding and grooving, joint resealing, crack sealing, and concrete overlays. Although this guide constitutes a useful overall resource on the topic of concrete pavement preservation, it does not specify maintenance actions or sur face prepa- rations that might serve as pre-treatments for pavement preservation. The guide treats the actions that are identified more as concurrent preservation actions than as maintenance before preservation. FHWA has developed a series of pavement preservation checklists for concrete pavement preservation that identify needed repairs prior to the application of the preservation treat- ment (https://www.fhwa.dot.gov/pavement/preservation/ppcl00.cfm). Among checklists for State Highway Agency Guidance Reference Illinois “In some cases, combinations of preservation strategies are needed to correct the combination of distress that is present on the pavement.” Evaluate all flexible pavement sections for the presence of bumps greater than 0.5 in. If the treatment does not include milling or recycling of the surface, grind the bumps prior to treatment placement. Illinois DOT (2010) Bureau of Design and Environment Manual, Chapter 52 Indiana “The type and severity of distresses on existing pavement are major factors in selecting a treatment.” Lee and Shields (2010) Indiana DOT Minnesota “Complete any crack treatments, spot patching, rut filling, or other required repairs prior to the placement of a preservation treatment.” Minnesota DOT (2019) MnDOT Pavement Preservation Manual Pennsylvania “Isolated or obvious deficiencies must always be evaluated and addressed if cost effective.” Pennsylvania DOT (2019) Publication 242, Pavement Policy Manual South Dakota “Bumps should be evaluated and ground prior to placing of the flexible treatment options that do not include milling or recycling of the pavement surface.” South Dakota DOT (2010) Pavement Preservation Guidelines Table 5. State highway agency guidance on the connection between preparation activities and pavement preservation. Source: American Concrete Pavement Association (2006). Figure 1. Recommended sequence of procedures used in concrete pavement restoration.

14 Maintenance and Surface Preparation Activities Prior to Pavement Preservation Treatments joint and crack sealing, diamond grinding, dowel bar retrofit, partial-depth repair, full-depth repair, cross stitching, and longitudinal diamond grooving—only the grinding and grooving checklists specify pre-treatment repairs. Those repairs are designed to ensure that broken or rocking slabs are repaired or replaced and to verify that other pavement repairs are conducted— except for the joint sealing and partial-depth repairs using elastomeric-based concrete, which are completed after grinding (Federal Highway Administration 2019). Timing An interval of time may be recommended between the completion of certain maintenance or surface preparation activities and the placement of a preservation treatment. This interval may be advisable because of the effect of the maintenance activity on the performance of preserva- tion, as a result of contracting or operational reasons, or in response to other constraints dictated by the project. For Kansas chip seals, Testa and Hossain (2014) report, “[T]here is no absolute time frame during which repair work must be accomplished. It is generally preferred all repair work must be accomplished well in advance (perhaps 8 to 10 months) before applying the seal coat.” They also state, “[I]t is very important for the local maintenance personnel to know when chip seals are scheduled in order to have the repair work completed in advance of the chip seal.” This conclusion is especially valid when a cold mix is used for asphalt patching so that sufficient time is allowed for the volatiles in the mix to evaporate. Minnesota’s guidance (Minnesota DOT 2019) considers the maintenance activity and advises that “when crack sealing is needed prior to a preventive maintenance treatment, the crack seal should be placed at least 1.5–3 months in advance to minimize difficulties and conflicts between treatment types and/or contractors.” This is similar to Illinois DOT recommendations that crack sealing, when needed prior to the placement of the preventive maintenance treatment, should optimally be completed at least 3 months before placement of the treatment (Illinois DOT 2010). The South Dakota DOT (2010) also offers similar advice about the timing of crack sealing, which it notes “should be placed at least 3 months in advance to minimize difficulties and conflicts between treatment types and/or contractors.” In research sponsored by the Washington State DOT and focused on chip seals, Mahoney et al. (2014) surveyed the practices of other agencies that follow a cyclic practice that incorporates chip seals and other preparation work as part of a timed approach to asphalt pavement resur- facing, reporting the following: • Montana: “In year 6 to 9 [after an HMA overlay], the roadway is crack sealed, followed by a chip seal the next year (year 7 to 10).” • South Dakota: When HMA overlays and chip seals are alternated, “a typical cycle starts with a HMA overlay. This is followed by a crack seal 2 years later and a chip seal in year 3.” • Nebraska: “A typical cycle starts with an HMA overlay, a crack seal in year 4, a chip seal in year 8, another chip seal in year 13 or 14, and finally an HMA overlay between years 18 and 20.” The South Dakota DOT (2010) Pavement Preservation Guidelines provide additional context regarding this cycle, calling for the inspection of newly constructed HMA surfaces 1 year after construction to detect any cracks; then those cracks are sealed, and a chip seal is placed in the second or third year. Tennessee DOT guidance on crack sealing indicates that “materials should be aged at least one year prior to microsurfacing, any type of Hot-Mix Overlay, or other treat- ment” (Tennessee DOT 2018).

Literature Review 15   Contracting In only a few instances do states address the matter of how maintenance and surface prep- aration before preservation are accomplished. In Kansas, milling and planing are “normally included with the chip seal contract, allowing the Contractor to coordinate the work” (Testa and Hossain 2014). Crack sealing or filling may be included in the chip seal contract, especially if many cracks must be sealed; however, the sealing of just a few cracks may be completed by DOT maintenance forces. Indiana does not specifically identify contracting differences between preparatory work and the preservation treatment itself but does note that “pavement preservation is split between in-house maintenance activities and contract work performed as part of the district’s pavement program. These programs must be synchronized, creating a seamless cycle of treatments to provide maximum life for the pavement system” (Lee and Shields 2010). Connecticut’s draft Pavement Preservation Manual (Connecticut DOT 2011) supplies addi- tional insight into the issue of timing in the context of evaluating the cost-effectiveness of a separate program to treat isolated distress: It is possible to treat isolated distress conditions as a separate program, where the work is completed prior to the application of the preservation treatment (say early in the season, or the prior year). The unit costs of isolated structural repairs, for instance, are high, because it is difficult to achieve high produc- tion rates and labor, equipment, and mobilization are significant cost components. Therefore, the agency should carefully evaluate the cost and feasibility of including these isolated repairs in a preservation project versus doing these repairs in house or through a separate maintenance or repair activity contract. Addressing isolated conditions in a separate program has the benefit of correcting isolated conditions where the preservation decision would be “do nothing” otherwise; it has the risk of paying for preparatory work when the preservation treatment is subsequently cancelled—these factors should be included in the decision of whether to implement such a program. New Mexico’s Pavement Maintenance Manual defines routine maintenance as work that is planned and performed routinely to maintain and preserve the condition of the highway system or to respond to specific conditions and events that require restoration of the highway system to an adequate level of service (New Mexico DOT n.d.). Routine maintenance consists of day- to-day activities that maintenance personnel schedule to maintain and preserve the highway system at a satisfactory level of service. Routine maintenance activities are often in-house or agency-performed activities. Performance In the relationship between maintenance and surface preparation prior to preservation, an underlying assumption is that such preparatory actions produce a positive effect on the subse- quent performance of the preservation treatment. A small number of studies examine the relationship between certain preparatory activities and preservation treatment performance. Washington State DOT research on preventive maintenance on HMA pavements focuses on the effectiveness of four treatments in extending pavement life: crack sealing, chip sealing, dig outs, and blade patching (Anderson et al. 2018). Two test sites in the Anderson et al. (2018) study consisted of crack sealing followed by chip sealing, and the authors concluded that “in both cases crack sealing prior to a chip seal prevented reflection cracking.” Six study sites included dig outs (HMA patches) followed by chip seals; the results were mixed, with some flushing, reflection cracking, and potholes observed in the chip seal surface (Anderson et al. 2018). A study on the National Center for Asphalt Technology Lee Road 159 test sections compared the performance of two preservation treatments—chip seals and microsurfacing, with and without

16 Maintenance and Surface Preparation Activities Prior to Pavement Preservation Treatments Source: National Center for Asphalt Technology (2019). Figure 2. Lee Road 159 microsurfacing sections without (left) and with (right) crack sealing prior to placement. crack sealing prior to the application of those treatments—as part of a larger study of the effects of pavement preservation on pavement life (Vargas-Nordcbeck and Jalali 2020). Early results for the sections receiving both (1) crack sealing and (2) either a chip seal or micro surfacing suggest that the reappearance of cracking is significantly delayed compared to the cracked sections that were treated only with either a chip seal or microsurfacing. In the National Center for Asphalt Technology (2019) study, crack sealing is referred to as a “pre-treatment” for the chip seal and microsurfacing sections. Figure 2 shows microsurfacing sections, both with and without a crack sealing pre-treatment.