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

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Preservation Treatment Summaries A P P E N D I X AThis appendix contains technical summaries for each of the preservation treatments covered in this document. The sum- maries, which are presented in a tabular format, include treatment descriptions, the key pavement conditions they32address, and construction and other considerations (includ- ing expected performance and estimated costs). They also provide a listing of reference materials that users can access to get up-to-date information on each treatment.

33Crack Sealing and Crack Filling Crack filling involves the placement of an adhesive material into and/or over nonworking cracks (typically longitudinal cold-joint and reflective cracks, edge cracks, and distantly spaced block cracks) at the pavement surface in order to prevent the infiltration of moisture into the pavement structure and reinforce the adjacent pavement. Crack filling operations generally entail minimal crack preparation and the use of lower-quality materials. Crack sealing involves the placement of an adhesive material into and/or over working cracks (i.e., those that open and close with temperature changes, such as transverse thermal and reflective cracks, diagonal cracks, and certain longitudinal reflective cracks) at the pavement surface in order to prevent the infiltration of moisture into the pavement structure. Crack sealing opera- tions typically require good crack preparation (i.e., routing or sawing a reservoir over the crack and power cleaning the reservoir) and the placement of high-quality flexible materials (i.e., thermosetting or thermoplastic bituminous materials that soften upon heating and harden upon cooling) into and possibly over the reservoir. Functional/Other • Longitudinal cracking • Transverse cracking • Reflection cracking • Minor block cracking • Material selection requirements to consider include adhesion, softening resistance, flexibility, pot life, weather resistance, and cure time. • In deciding between hot- and cold-applied crack fillers, consider the size and types of cracks. Hot-applied crack fillers are better suited to 0.5 in. wide or larger expanding cracks (large longitudinal, transverse, and reflective cracks), while cold crack fillers work better in smaller cracks less than 0.5 in. wide. • Cracks should be clean and dry. Cleaning is essential to good bond and maximum performance. • A variety of placement configurations are used based on local experience, materials, snow plow use, anticipated subse- quent treatments, and aesthetic considerations. • Sealants and fillers should be allowed to set before being subjected to traffic. • Sealants and fillers require curing before another treatment is applied to the surface. Emulsions usually require several days to cure, while hot-applied crack fillers take 3 to 4 months. Cost (Relative Cost, $ to $$$$): • Crack filling: $0.10 to $1.20/ft ($) • Crack sealing: $0.75 to 1.50/ft ($) • Safety: Extensive crack sealing may require blotting to maintain the pavement’s skid resistance. • Risk: Improper installation can cause sealant or filler material to fail. Overband applications should be avoided on heavily trafficked roadways due to high tensile stresses directly above crack edges, resulting in edge separations. Overband applications are susceptible to snowplow damage. • Climate: Placement should take place during moderate temperatures when the pavement is dry. The manufacturer’s guidelines should be followed, but a good range of ambient temperatures is 45°F to 65°F. • Tracking of seal or fill material by tire action may obscure lane markings and adversely affect skid resistance. Applying a blotter coat of sand can reduce such “tracking.” There are other products and means available to reduce surface tackiness. • There is a point at which excessive cracking is better addressed by a “blanket” solution, such as a surface treatment or milling. Aesthetic considerations may limit the acceptable amount of crack sealed surface. • Rough riding surface may occur during warm months when sealant or filler material is compressed and bulges out of the crack. • Manual of Practice: Materials and Procedures for Sealing and Filling Cracks in Asphalt-Surfaced Pavements. Report FHWA- RD-99-147. Federal Highway Administration, U.S. Department of Transportation, 1999. • Pavement Preservation Checklist Series: 1. Crack Seal Application. Publication FHWA-IF-02-005. Federal Highway Adminis- tration, U.S. Department of Transportation, 2001. Table A.1. Technical Summary for Crack Sealing and Crack Filling T re a tm e n t D e sc ri p ti o n C o n d it io n s A d d re ss e d Structural: Crack sealing may be applied to structural (i.e., fatigue or reflection) cracks early in their development. While sealing provides no structural benefit, keeping moisture out of the pavement structure may slow down the progression of load-related cracking. Noise: Overband applications may increase pavement noise. Similarly, wide cracks contribute to a louder riding surface. C o n st ru c ti o n C o n si d e ra ti o n s M is c e lla n e o u s C o n si d e ra ti o n s Treatment Life (yr): • Crack filling: 2 to 4 • Crack sealing: 3 to 8 Pavement Life Extension (yr): • Crack filling: NA • Crack sealing: 2 to 5 A d d it io n a l R e so u rc e s O th e r R e m a rk s

34Slurry Seals Slurry seals are a mixture of well-graded aggregate (fine sand and mineral filler) and asphalt emulsion that is spread over the entire pavement surface with either a squeegee or spreader box attached to the back of a truck. Slurry seals are effective in sealing low-severity surface cracks, waterproofing the pavement surface, and improving friction at speeds below 30 mph. Functional/Other • Longitudinal cracking • Transverse cracking • Raveling/weathering • Friction loss • Moisture infiltration • Roughness • Special consideration should be given to raised pavement markers and bump grinding prior to treatment placement. • It is strongly recommended to address needed patching and crack sealing prior to placement. • Pavement surface must be dry and swept clean of dirt, sand, gravel, and other surface contaminants. • Aggregates should be clean, angular/cubical, durable, and uniform. • Industry guidelines and recommendations regarding application temperatures and dry conditions should be followed. Cost (Relative Cost, $ to $$$$): • Single-course: $0.75 to $1.00/yd2 ($$) • Risk: Slurry seals can accelerate the development of stripping in susceptible HMA pavements. • Climate: Slurry seals perform effectively in all climatic conditions. However, best performance occurs in warm climates with low daily temperature cycles. • Slurry seals can be modified (i.e., aggregate quality, gradation) to accommodate higher traffic volumes (Type 3). • Dusting with a blotter material can allow earlier opening of intersections and turning lanes. • Recommended Performance Guidelines for Emulsified Asphalt Slurry Seal. Report A105. International Slurry Surfacing Association, Annapolis, Md., 2005. • Pavement Preservation Checklist Series: 13. Slurry Seal Application. Publication FHWA-IF-06-014. Federal Highway Administration, U.S. Department of Transportation, 2005. • Slurry Seal/Micro-Surface Mix Design Procedure. Phase I Report, Caltrans Project 65A0151. California Department of Transportation, Sacramento, 2004. Table A.2. Technical Summary for Slurry Seals T re a tm e n t D e sc ri p ti o n C o n d it io n s A d d re ss e d Structural: Slurry seals do not add structural capacity. Pavement with cracking and areas of high deflection are not good candidates for slurry seals. Noise: Slurry seals are partly capable of reducing tire–pavement noise. C o n st ru c ti o n C o n si d e ra ti o n s M is c e lla n e o u s C o n si d e ra ti o n s Treatment Life (yr): • 3 to 5 Pavement Life Extension (yr): • 4 to 5 O th e r R e m a rk s A d d it io n a l R e so u rc e s

35Microsurfacing Microsurfacing is a mixture of crushed, well-graded aggregate, mineral filler (portland cement), and latex-modified emulsified asphalt spread over the full width of pavement with either a squeegee or spreader box. Microsurfacing is used primarily to inhibit raveling and oxidation, as well as being effective at improving surface friction and filling minor irregularities and rutting (up to 1.5 in. deep). Microsurfacing is usually applied in either a single or double application. A double application involves a rut-filling application followed by a full-lane width application. Functional/Other • Longitudinal cracking • Transverse cracking • Raveling/weathering • Friction loss • Moisture infiltration • Bleeding • Roughness • Special consideration should be given to raised pavement markers and bump grinding prior to treatment placement. • It is strongly recommended to address needed patching and crack sealing prior to placement. • Pavement surface must be dry and swept clean of dirt, sand, gravel, and other surface contaminants. • Aggregates should be clean, angular/cubical, durable, and uniform, as well as chemically compatible with emulsion system. • Industry guidelines and recommendations regarding application temperatures and dry conditions should be followed. • Microsurfacing typically can carry traffic after approximately 1 hour. • Allow minimum 7 days before applying permanent pavement markers and striping. Cost (Relative Cost, $ to $$$$): • Single-course: $1.50 to $3.00/yd2 ($$) • Risk: Early damage can occur at down grade locations or where there is heavy truck turning; in such areas, rolling before opening to traffic may improve durability. Vehicle damage can occur if seals do not set or bond, which will occur if placed during inclement weather. • Climate: Placement should occur when temperature is 50°F and rising, and the forecast for the next 24 hours is above 40°F. Placement should avoid rain and hot or freezing temperatures. • Similar to slurry seals, microsurfacing can be modified (i.e., aggregate quality, gradation) to also accommodate higher traffic volumes. • Dusting with a blotter material can allow earlier opening of intersections and turning lanes. • Recommended Performance Guidelines for Microsurfacing. Report A143. International Slurry Surfacing Association, Annapolis, Md., 2005. • Pavement Preservation Checklist Series: 5. Microsurfacing Application. Publication FHWA-IF-03-002. Federal Highway Administration, U.S. Department of Transportation, 2002. • Slurry Seal/Micro-Surface Mix Design Procedure. Phase I Report, Caltrans Project 65A0151. California Department of Transportation, Sacramento, 2004. Table A.3. Technical Summary for Microsurfacing T re a tm e n t D e sc ri p ti o n C o n d it io n s A d d re ss e d Structural: Microsurfacing does not add structural capacity. However, it can seal low- severity cracks, including fatigue cracks, and can be used to fill stable rutting up to 1.5 in. deep. Pavement with cracking and areas of high deflection are not good candidates for microsurfacing. Noise: Microsurfacing may reduce tire–pavement noise depending on the aggregate used. C o n st ru c ti o n C o n si d e ra ti o n s M is c e lla n e o u s C o n si d e ra ti o n s Treatment Life (yr): • Single-course: 3 to 6 • Multiple-course: 4 to 7 Pavement Life Extension (yr): • Single-course: 3 to 5 • Multiple-course: 4 to 6 O th e r R e m a rk s A d d it io n a l R e so u rc e s

36Chip Seals Chip seals consist of a sprayed application of asphalt (commonly an emulsion, although heated asphalt cement and cutbacks are used as well) directly to the pavement surface (0.35 to 0.50 gal/yd2), followed by application of aggregate chips (15 to 50 lb/yd2), which are then immediately rolled to achieve 50% to 70% embedment. The treatment is used to seal the pavement surface against weathering, raveling, or oxidation, correct minor roughness or bleeding, and improve friction. Chip seals can be applied in multiple layers (e.g., double chip seal), and in combination with other treatments, such as microsurfacing, which is called a cape seal and reduces concerns associated with loose chips and a rough surface. Chip seal design variations include the following (Gransberg and James 2005): • Racked-in-seal. Chip seal that is temporarily protected from damage through the application of choke stone that becomes locked in the voids, preventing aggregate particles from dislodging before the binder is cured. Often used in locations where there are large numbers of turning movements. • Sandwich seal (dry-matting). Chip seal involving one binder application sandwiched between two separate aggregate applications. Particularly useful for restoring surface texture on raveled surfaces. • Inverted seal. Inverted double chip seal, in which a smaller-sized aggregate chip seal is placed first, followed by a larger-sized aggregate chip seal. • Cape seal. Combination of a chip seal and slurry seal, with the slurry seal placed atop the chip seal typically 4 to 10 days after placement of the chip seal. Primary purposes are the same as a chip seal; the slurry cover increases the life of the chip seal by the enhanced binding of the aggregate chips. • Geotextile-reinforced seal. Application of geotextile over a tack coat, followed by application of a single-course chip seal. Functional/Other • Longitudinal cracking • Transverse cracking • Block cracking • Friction loss • Bleeding • Roughness • Moisture infiltration • Application rates depend upon aggregate gradation and maximum size, as well as absorption of existing pavement surface. • Special consideration should be given to raised pavement markers and bump grinding prior to treatment placement. • Pavement surface must be dry and swept clean of dirt, sand, gravel, and other surface contaminants. • Chip spreader should follow immediately behind asphalt distributor and rollers close behind spreader. • Normal traffic speeds should not resume until after curing (typically 2 hours). • Avoid prematurely applying permanent pavement markers and striping. • Brooming is often required to remove loose chips; however, brooming before the emulsion has set hard may strip away properly seated aggregate. Cost (Relative Cost, $ to $$$$): • Single-course conventional: $1.50 to $2.00/yd2 ($$) • Single-course polymer-modified: $2.00 to $4.00/yd2 ($$$) • Safety: Loose aggregate may increase stopping distance, reduce vehicle control. • Risk: Primary risk is due to damage claims from loose aggregate. Pilot cars can be used to minimize damage to the fresh surface, as well as windshield/vehicle damage due to whip-off on high speed roadways. • Climate: Performs well in all climatic environments. Placement should occur when the temperature in the shade is above 55°F. Avoid placement during cold and/or wet weather conditions. • With special design and placement considerations, treatment can perform well on high-volume roads. For example, use a rapid-set emulsion or polymer- or rubber-modified binder in the mix design, apply a smaller sized “choke” aggregate to lock in larger chips, limit excess chips to 5% to 10%, or apply a cape seal (slurry or microsurfacing seal over the chip seal). • The dusting of a blotter material can be used to allow for earlier opening of intersections and turning lanes. • Gransberg, D., and D. M. B. James. NCHRP Synthesis of Highway Practice 342: Chip Seal Best Practices. Transportation Research Board of the National Academies, Washington, D.C., 2005. • Pavement Preservation Checklist Series: 2. Chip Seal Application. Publication FHWA-IF-02-046. Federal Highway Administration, U.S. Department of Transportation, 2002. Table A.4. Technical Summary for Chip Seals T re a tm e n t D e sc ri p ti o n C o n d it io n s A d d re ss e d Structural: Adds no structural benefit. Because of its flexibility, a chip seal is more effective at sealing low- to medium-severity fatigue cracks in comparison with other treatments. Noise: Will typically require application of a slurry seal or microsurfacing to provide a quiet riding surface. C o n st ru c ti o n C o n si d e ra ti o n s M is c e lla n e o u s C o n si d e ra ti o n s Treatment Life (yr): • Single-course: 3 to 7 • Double-course: 5 to 10 Pavement Life Extension (yr): • Single-course: 5 to 6 • Double-course: 8 to 10 O th e r R e m a rk s A d d it io n a l R e so u rc e s

37Ultra-Thin Bonded Wearing Course Also known as an ultra-thin friction course, an ultra-thin bonded wearing course may be used as an alternative treatment to chip seals, microsurfacing, or thin HMA overlays. This consists of a gap-graded, polymer-modified HMA layer (0.4 to 0.8 in. thick) placed on a tack coat (heavy, polymer-modified emulsified asphalt). It is effective at treating minor surface distresses and increasing surface friction. Functional/Other • Longitudinal cracking* • Transverse cracking* • Block cracking* • Raveling/weathering • Friction loss • Bleeding • Roughness • Requires special paving equipment and a license to place. • Special consideration should be given to bump grinding prior to treatment placement. • Cracks greater than 0.25 in. wide should be sealed prior to placement. • Strongly recommended to repair localized structural problems prior to placement. • Pavement surface must be dry and swept clean of dirt, sand, gravel, and other surface contaminants. Oil and fuel stains should be thoroughly cleaned as well. • Treatment can be opened to traffic shortly after the rolling operation is complete and the material has cooled below 185°F (potentially as soon as half an hour after placement). Cost (Relative Cost, $ to $$$$): • $4.00 to 6.00/yd2 ($$$) • Climate: Performs well in all environments. Placement should occur when the temperature is above 50°F. Avoid placement during cold and/or wet weather conditions. Placement on a damp pavement surface is acceptable; however, the pavement should be free of standing water, and favorable weather conditions should be expected to follow. • Typically a proprietary product (e.g., NovaChip). • Capable of withstanding high ADT and truck levels better than many other thin treatments. Table A.5. Technical Summary for Ultra-Thin Bonded Wearing Course T re a tm e n t D e sc ri p ti o n C o n d it io n s A d d re ss e d Structural: Treatment does not add structural benefit, but does retard fatigue cracking and can address stable rutting less than 0.5 in. deep. Noise: Effective tire-pavement noise reduction similar to that of open-graded, thin HMA overlays. C o n st ru c ti o n C o n si d e ra ti o n s M is c e lla n e o u s C o n si d e ra ti o n s Treatment Life (yr): • 7 to 12 Pavement Life Extension (yr): • NA O th e r R e m a rk s A d d it io n a l R e so u rc e s *High severity cracking can be better addressed with cold milling and overlay.

38Thin and Ultra-Thin HMA Overlays (with or without milling) Thin and ultra-thin HMA overlays are composed of asphalt binder and aggregate combined in a central mixing plant and placed with a paving machine in thicknesses ranging from 0.625 to 0.75 in. for ultra-thin and 0.875 to 1.50 in. for thin. Conventional HMA overlays can be distinguished by their aggregate gradation: • Dense graded. A well-graded, relatively impermeable mix, intended for general use. • Open graded. An open-graded, permeable mix designed using only crushed aggregate and a small percentage of manufactured sand; typically smoother than dense-graded HMA. • Stone matrix asphalt (SMA). A gap-graded mix designed to maximize rut resistance and durability using stone-on-stone contact. Additionally, it is recommended to mill the existing pavement surface when surface distresses (e.g., segregation, raveling, or block crack- ing) are evident; other benefits include improving surface friction, maintaining clearance of overhead structures, and providing an improved bonding surface. Functional/Other • Longitudinal cracking • Transverse cracking • Raveling/weathering • Block cracking • Friction loss • Bleeding • Roughness • Splash and spray (open graded) • Maximum size aggregate should not be more than one-half the overlay thickness (note that Superpave mix designs have their own requirements). • If milling is not done in conjunction with overlay application, special consideration should be given to bump grinding prior to treat- ment placement. • Pavement surface must be dry and swept clean of dirt, sand, gravel, and other surface contaminants; a tack coat applied prior to overlay application will improve bond to existing surface. • Because thin and ultra-thin HMA overlays dissipate heat rapidly, it is important to specify minimum placement temperatures and to obtain timely compaction. • Treatment can be opened to traffic after approximately 1 to 2 hours. Recommendations for obtaining a quality milled surface: • Perform pavement patching prior to milling. • Remove pavement castings and cover holes prior to milling. • Use a good working milling machine (12-ft recommended width). • Control milling speed to achieve a smooth, uniform surface (≤30 ft/min). • Use a 30-ft ski and stringline to control grade and longitudinal guidance. Cost (Relative Cost, $ to $$$$): • Dense-graded ultra-thin: $2.00 to $3.00/yd2 ($$) • Dense-graded thin (no milling): $3.00 to $6.00/yd2 ($$$) • Dense-graded thin (with milling): $5.00 to $10.00/yd2 ($$$) • Risk: Though not significantly affected by ADT or truck levels, certain combinations of loadings, environmental conditions, and pave- ment structure can initiate top-down cracking. Performance will vary according to factors affecting pavement weathering/raveling. Further- more, treatment can be subject to delamination and reflective cracking. A tack coat prior to overlay placement will help improve bond. • Climate: Dense-graded and gap-graded mixes perform well in all environments. The performance of open-graded mixes can be significantly adversely impacted by freeze-thaw environments. • Newcomb, D. E. Information Series 135: Thin Asphalt Overlays for Pavement Preservation. National Asphalt Pavement Association, Lanham, Md., 2009. • Pavement Preservation Checklist Series: 3. Thin HMA Overlay Application. Publication FHWA-IF-02-049. Federal Highway Administration, U.S. Department of Transportation, 2002. Table A.6. Technical Summary for Thin and Ultra-Thin HMA Overlays T re a tm e n t D e sc ri p ti o n C o n d it io n s A d d re ss e d Structural: While thin and ultra-thin HMA overlays should not be used to address structural deficiencies, greater structural benefit in terms of load-carrying capability is possible the thicker the overlay. Rutting can be addressed with a separate rut-fill application before overlay placement. Noise: Open-graded thin HMA overlays are effective at reducing tire–pavement noise. Cold milling provides a smoother riding surface by removing vertical deformations. C o n st ru c ti o n C o n si d e ra ti o n s M is c e lla n e o u s C o n si d e ra ti o n s Treatment Life (yr): • Dense-graded ultra-thin: 4 to 8 • Dense-graded thin (no milling): 5 to 12 • Dense-graded thin (with milling): 5 to 12 Pavement Life Extension (years): • Dense-graded ultra-thin: NA • Dense-graded thin: (no milling): NA • Dense-graded thin: (with milling): NA O th e r R e m a rk s A d d it io n a l R e so u rc e s

39Hot In-Place Recycling As a preservation treatment, hot in-place recycling (HIR) corrects surface distresses within the top 2 in. of an existing HMA pavement by softening the surface material with heat, mechanically loosening it, and mixing it with recycling agent, aggregate, rejuvenators, and/or virgin asphalt. HIR consists of three different techniques: • Surface recycling. Pavement surface (typically top 0.5 to 1.5 in.) is heated, loosened, combined with new asphalt, and relaid for the purpose of minor mix improvement/modification. In single-pass surface recycling (low-volume roads), the recycled mix is relaid and serves as the final wearing surface. In double-pass surface recycling (moderate- to high-volume roads), an HMA overlay or a surface treat- ment is applied over the recycled surface. • Remixing. Pavement is heated, loosened, combined with virgin aggregate and new asphalt (and/or new HMA), and relaid for signifi- cant mix improvement/modification and/or modest pavement strengthening. The recycled mix can serve as the final wearing surface (low- volume roads) or can serve as a base for an HMA overlay or surface treatment (moderate- to high-volume roads). • Repaving. Pavement surface is heated, loosened, combined with new asphalt, and relaid in tandem with an HMA overlay for the purposes of pavement strengthening and restoration of surface profile and/or friction. Repaving is surface recycling with an integrally applied thermally bonded overlay. Functional/Other • Alligator, thermal, and surface cracking • Raveling/weathering • Friction loss • Bleeding • Roughness • Corrugation • Rutting • Requires a length train of specialized equipment. • Recommended to repair localized structural problems prior to placement. • Presence of rubber in the surface lift (e.g., rubberized seals, some crack fillers) requires special attention during the HIR mix design process. • Pavement surface must be dry and swept clean of dirt, sand, gravel, and other surface contaminants. • Like HMA overlays, treatment can be opened to traffic after approximately 1 to 2 hours. Cost (Relative Cost, $ to $$$$): • Surface recycle (excluding thin HMA overlay): $2.00 to $3.00/yd2 ($$) • Remix (excluding thin HMA overlay): $3.00 to $6.00/yd2 ($$$) • Repaving: $3.50 to $7.00/yd2 ($$$) • Safety: Crack sealant should be removed prior to placement to reduce risk of flash fires or excessive blue smoke. • Climate: Although HIR treatment can perform well in all climatic conditions, placement should not occur when temperature is below 50°F, or when it is raining. • HIR is appropriate for low- to high-volume roads; however, the surface recycling and remixing techniques should be supplemented with an overlay or surface treatment when used on moderate- to high-volume roads. Also, because the recycling equipment is relatively large, short road sections, particularly in urban settings, are not suitable. • HIR can be expected to produce about 1 to 2 lane mi/day. However, nighttime operations will be subject to reduced production rates and increased cost. • Basic Asphalt Recycling Manual. Asphalt Recycling and Reclaiming Association, Annapolis, Md., 2004. • Pavement Recycling Guidelines for State and Local Governments: Participant’s Reference Book. Publication FHWA-SA-98-042. Federal Highway Administration, U.S. Department of Transportation, 1997. • Pavement Preservation Checklist Series: 11. Hot In-Place Recycling Application. Publication FHWA-IF-06-011. Federal Highway Administration, U.S. Department of Transportation, 2005. Table A.7. Technical Summary for Hot In-Place Recycling T re a tm e n t D e sc ri p ti o n C o n d it io n s A d d re ss e d Structural: Treatment may add some structural benefit if additional surfacing is placed, and will reduce surface rutting. However, HIR is not recommended where there are excessive subgrade failures, wide cracking, or HMA thickness less than 3 in. Noise: Dependent on type and characteristics of finished surface. For example, HIR accompanied by an HMA overlay will result in a low-noise pavement, whereas higher noise levels will be experienced by HIR “capped” with a chip seal. C o n st ru c ti o n C o n si d e ra ti o n s M is c e lla n e o u s C o n si d e ra ti o n s Treatment Life (yr): • Surf recycle and HMA overlay: 6 to 10 • Remix and thin HMA overlay: 7 to 15 • Repaving: 6 to 15 Pavement Life Extension (yr): • Surf recycle and HMA overlay: NA • Remix and thin HMA overlay: NA • Repaving: NA O th e r R e m a rk s A d d it io n a l R e so u rc e s

40Cold In-Place Recycling Cold in-place recycling (CIR) is a process that consists of milling and sizing reclaimed asphalt pavement (RAP) and mixing in-place the RAP with recycling additive and new aggregate (either in the milling machine’s cutting chamber or in a mix paver) to produce a recycled cold mix, which is then relaid and compacted as a new base course. As a preservation treatment, CIR is primarily used to restore profile/cross-slope and/or mitigate surface and other upper-layer distresses. Its depth of application in a preservation capacity is limited to 3 to 4 in. For moderate- to high-volume roadways, the CIR recycled layer is accompanied by an overlay or surface treatment. Functional/Other • Longitudinal, transverse, and surface cracking • Raveling/weathering • Friction loss • Bleeding • Roughness • Corrugation • Rutting • Bumps/sags • Requires a lengthy train of specialized equipment, which can create difficulties when working on roads with tight situations or when the project has limited areas for overnight parking/storage of the equipment. • Recommended to repair localized structural problems prior to placement. • Presence of rubber in the surface lift (e.g., rubberized seals, some crack fillers) requires special attention during the CIR mix design process. • Pavement surface must be dry and swept clean of dirt, sand, gravel, and other surface contaminants. • Depending on the type of emulsion used and the environmental conditions, the CIR-recycled layer can be compacted after 1 to 2 hours, when the emulsion begins to break. • Placement of an HMA wearing course or surface treatment on the CIR-recycled layer requires that the recycled layer be given proper curing time (typically, 10 to 14 days). Cost (Relative Cost, $ to $$$$): • CIR (excluding thin HMA overlay): $1.25 to $3.00/yd2 ($$) • Climate: Curing problems can occur if CIR is undertaken in cold, damp conditions typical of late fall or early spring weather. • Basic Asphalt Recycling Manual. Asphalt Recycling and Reclaiming Association, Annapolis, Md., 2004. • Pavement Recycling Guidelines for State and Local Governments: Participant’s Reference Book. Publication FHWA-SA-98-042. Federal Highway Administration, U.S. Department of Transportation, 1997. • Cold Recycling Manual, 2nd ed. Wirtgen Group, Windhagen, Germany, 2004. • Pavement Preservation Checklist Series: 12. Cold In-Place Recycling Application. Publication FHWA-IF-06-012. Federal Highway Administration, U.S. Department of Transportation, 2005. Table A.8. Technical Summary for Cold In-Place Recycling T re at m en t D es cr ip ti o n C o nd it io ns A d d re ss ed Structural: CIR may add some structural benefit if additional surfacing is placed, and it will reduce surface rutting. As a preservation treatment, CIR is not recommended where there are excessive subgrade failures, wide cracking, or HMA thickness less than 3 in. Noise: Dependent on type and characteristics of finished surface. For example, CIR accompa- nied by an HMA overlay will result in a low-noise pavement, whereas higher noise levels will be experienced by CIR “capped” with a chip seal. C o ns tr uc ti o n C o ns id er at io ns O th er R em ar ks A d d it io na l R es o ur ce s M is ce lla ne o us C o ns id er at io ns Treatment Life (yr): • CIR and thin HMA overlay: 6 to 15 Pavement Life Extension (yr): • CIR and thin HMA overlay: NA

41Ultra-Thin Whitetopping Ultra-thin whitetopping (UTW) involves the placement of a thin (2 to 4 in.) PCC layer, with slab dimensions between 2 and 6 ft, over an existing HMA-surfaced pavement. The primary purpose of UTW is to eliminate surface distresses (e.g., raveling and cracking), correct various forms of deformation (e.g., corrugations and rutting), and improve friction and smoothness. Functional/Other • Longitudinal, transverse, and surface cracking • Raveling/weathering • Friction loss • Roughness • Corrugation • Rutting • Shoving • Before placement, distresses in the existing HMA pavement should be repaired, after which the surface should be cleaned (a mechanical broom or low pressure washer are adequate) of material detrimental to bonding the overlay to the existing pavement. • Just before placement, the HMA surface should be lightly wetted (no pools of water) to prevent water from being drawn from the fresh concrete. • If fiber reinforcement is used, efforts to minimize fiber balling should be taken. • During placement, concrete should be placed evenly across the width of the paving area to avoid segregation and minimize additional spreading. • Floating should be kept to a minimum. If finishing requires the frequent use of floats, adjustments may need to be made to the concrete mix or finishing machines. • When whitetopping an uneven surface, placement should be such that the design thickness is maintained at the thinnest sections. • Timing joint cutting is critical in preventing early age distress; sawing too early can result in raveling, while sawing too late may lead to random cracking. Early entry sawing can help to ensure that the joints are cut in a timelier manner. • Opening to traffic is contingent upon concrete strength development and joint sawing. Cost (Relative Cost, $ to $$$$): • $15.00 to $25.00/yd2 ($$$$) • Risk: Lack of bond can result in corner breaks and/or surface failure. • Climate: Although UTW can perform well in all climatic conditions, placement should not occur when temperature is below 50°F, or when it is raining. During construction, the most detrimental effects of climatic conditions occur at extreme temperature conditions, specifi- cally at air temperatures greater than 90°F or less than 39°F. • If not inlaid, curb and gutter may need to be replaced to meet the elevation of the UTW treatment. • Transitions to adjacent pavement can be susceptible to damage if measures are not taken to provide adequate support or load transfer, such as gradually increasing whitetopping thickness to meet that of a new full-depth pavement or installing expansion joints for transitioning to an existing pavement. • Rasmussen, R. O., and D. K. Rozycki. NCHRP Synthesis of Highway Practice 338: Thin and Ultra-Thin Whitetopping. Transportation Research Board of the National Academies, Washington, D.C., 2004. Table A.9. Technical Summary for Ultra-Thin Whitetopping T re at m en t D es cr ip ti o n C o nd it io ns A d d re ss ed C o ns tr uc ti o n C o ns id er at io ns O th er R em ar ks A d d it io na l R es o ur ce s M is ce lla ne o us C o ns id er at io ns Structural: UTW provides structural benefit, bonding to the existing HMA to increase load- carrying capacity. However, because UTW is a composite, the existing pavement and subbase should be structurally sound themselves to ensure overlay performance. Noise: Noise considerations are typical of PCC pavements. On high-speed facilities in noise- sensitive environments, certain forms of texturing, such as longitudinal tining, are more suitable than other forms, such as uniform transverse tining, because they generate lower pavement–tire noise. Producing smooth UTW surfaces also requires care during placement, such as maintaining consistent concrete production and avoiding interruptions in the forward motion of the screed or paver, which can lead to a bump or irregularities in the surface. Treatment Life (yr): • NA Pavement Life Extension (yr): • NA

42Joint Resealing and Crack Sealing Joint resealing and crack sealing of PCC pavements prevents moisture and incompressible materials from infiltrating the pavement struc- ture. This helps to slow or minimize the development of moisture-related distresses (such as pumping or faulting) and to prevent the occur- rence of spalling, blowups, and other pressure-related distresses that might be caused by incompressible materials collecting in the joints. Joint resealing consists of removing existing deteriorated transverse and/or longitudinal joint sealant (if present), refacing and pressure- cleaning the joint sidewalls, and installing new sealant material (liquid sealants generally require the installation of backer rod to prevent the sealant from seeping down in the joint). Crack sealing consists of sawing, power cleaning, and sealing cracks (typically transverse, longitudinal, and corner-break cracks wider than 0.125 in.) in concrete pavement using high-quality sealant materials. It is primarily intended to slow the rate of deterioration by preventing the intrusion of incompressible materials and reducing the infiltration of water into the crack. Functional/Other • Longitudinal cracking* • Transverse cracking • Corner cracking* • Critical material characteristics to consider when selecting a sealant include adhesiveness, cohesiveness, durability, extensibility, resilience, curing time, and shelf/pot life. • Effective cleaning of the joint or crack is essential to achieving good bond and ultimately the performance of the sealant. The old sealant material must be removed from each joint/crack face, either by sawing or through mechanical means. After removal of the sealant material, the joint/crack faces should be sandblasted to remove any slurry or laitance. • A variety of placement configurations may be employed, the selection of which is based on the sealant material used, local experi- ence, snow plow use, anticipated subsequent treatments, and aesthetic considerations. • Sealants should be “tack free” before being subjected to traffic (typically 1 to 2 hours). Cost (Relative Cost, $ to $$$$): • Joint resealing: $1.00 to $2.50/ft ($) • Crack sealing: $0.75 to $2.00/ft ($) • Risk: Improper installation can cause the sealant or filler material to fail. Overband applications should be avoided on heavily trafficked roadways due to high tensile stresses directly above crack edges, resulting in edge separations. Overband applications are also susceptible to snow plow damage. • Climate: Performs well in all climatic environments. Sealants perform best in dry, warm environments without large daily tempera- ture cycles. Placement should take place when the pavement is dry and during moderate temperatures (typically 45°F to 65°F, although the manufacturer’s recommendations should be followed). • Because resealing concrete joints is not a seasonal maintenance activity, periodic inspections should be scheduled to determine when treatment is necessary. • If tracking is a concern, a detackifier or toilet paper can be applied. • Increases in pavement roughness may occur during warm months when the sealant or filler material is compressed and bulges out of the joint or crack, particularly on long-jointed pavements or when excessive sealant was applied. • Manual of Practice: Materials and Procedures for Repair of Joint Seals in Portland Cement Concrete Pavement Joints. Report FHWA-RD-99-146. Federal Highway Administration, U.S. Department of Transportation, 1999. • Smith, K. D., T. E. Hoerner, and D. G. Peshkin. Concrete Pavement Preservation Workshop—Reference Manual. Federal Highway Administration, U.S. Department of Transportation, 2008. • Pavement Preservation Checklist Series: 6. Joint Sealing PCC Pavements. Publication FHWA-IF-03-003. Federal Highway Administration, U.S. Department of Transportation, 2002. *Crack sealing is most effective when cracks do not exhibit faulting or spalling. Table A.10. Technical Summary for Joint Resealing and Crack Sealing T re at m en t D es cr ip ti o n C o nd it io ns A d d re ss ed Structural: Crack sealing may be applied to structural cracks early in their development. While sealing provides no structural benefit, keeping moisture and incompressible materials out of the pavement struc- ture may retard the rate of deterioration. Noise: Overband applications and wide joints/cracks may generate excessive noise levels under traffic. C o ns tr uc ti o n C o ns id er at io ns O th er R em ar ks A d d it io na l R es o ur ce s M is c e lla n e o u s C o n si d e ra ti o n s Treatment Life (yr): • Joint resealing: 2 to 8 • Crack sealing: 4 to 7 Pavement Life Extension (yr): • Joint resealing: 5 to 6 • Crack sealing: NA

43Diamond Grinding and Grooving Diamond grinding consists of removing a thin layer of concrete (usually between 0.12 and 0.25 in.) from the pavement surface, using special equipment fitted with a series of closely spaced diamond saw blades. Diamond grinding removes joint faulting and other surface irregularities, thereby restoring a smooth-riding surface while also increasing surface friction and reducing noise emissions. Diamond grooving consists of cutting narrow, discrete grooves into the pavement surface, which helps to reduce hydroplaning, vehicle splash and spray, and wet-weather crashes. The grooves may be created in the pavement either longitudinally (in the direction of traffic) or transversely. Longitudinal grooving is more commonly done on in-service roadways because it is less intrusive to adjacent traffic lane operations; transverse grooving provides a more direct drainage route and contributes to braking forces, but may also contribute to noise emissions. Functional/Other • Joint faulting (grinding) • Slab curling/warping (grinding) • Friction loss (grinding/grooving) • Splash and spray (grooving) • Aggregate type and hardness must be known because this will influence costs and productivity. • Transverse grooving will be more difficult to do under traffic. • Spacing of the diamond grinding saw blades is critical to the life expectancy and friction of the resulting pavement texture. For soft aggregate (such as limestones), the spacing between blades is typically about 0.10 in., whereas for harder aggregate (such as river gravels) the spacing between blades is on the order of 0.08 in. • Grinding slurry must be collected on-site and disposed of in accordance with local regulations. • Slab stabilization, full-depth repairs, and spall repairs should be completed prior to grinding. Joint resealing should follow grinding to ensure proper sealant depth. • Diamond grooving should be done according to recommendations of the International Grinding and Grooving Association (IGGA, www.igga.net), which specifies 0.75 in. spacing and 0.125 in. width and depth. Cost (Relative Cost, $ to $$$$): • Diamond grinding: $1.75 to $5.50/yd2 ($$) • Diamond grooving: $1.25 to $3.00/yd2 ($$) • Safety: Safety is improved by restoring pavement surface texture, providing directional stability and increasing skid resistance, and reducing potential for hydroplaning, as well as lane-shoulder drop-off; furthermore, diamond grooving reduces splash and spray visibility issues associated with wet weather. • Risk: Though diamond grinding addresses pavement faulting, if the faulting mechanisms (e.g., poor load transfer, pumping, loss of support) are not addressed, faulting will reoccur. Also, more frequent grinding may be necessary to maintain surface friction on high- traffic-volume roadways where polishing of the aggregate is a problem, especially if soft aggregate was used. • Climate: Climate and age may most significantly impact the rate of macrotexture reduction on a diamond-ground surface; wet-freeze areas generally exhibit larger macrotexture reduction than dry, nonfreeze areas. • Usually, PCC pavements can be ground up to three times without significantly affecting fatigue life. • Can be accomplished during off-peak hours with short lane closures and without encroaching into adjacent lanes. • Neither grinding nor grooving affect overhead clearances, bridge approach elevations, or the hydraulic capacity of curbs and gutters. • Smith, K. D., T. E. Hoerner, and D. G. Peshkin. Concrete Pavement Preservation Workshop—Reference Manual. Federal Highway Administration, U.S. Department of Transportation, 2008. • Federal Highway Administration, U.S. Department of Transportation. Concrete Pavement Rehabilitation Guide for Diamond Grinding. www.fhwa.dot.gov/pavement/concrete/diamond.cfm. Accessed Oct. 13, 2010. • Pavement Preservation Checklist Series: 7. Diamond Grinding of PCC Pavements. Publication FHWA-IF-03-040. Federal Highway Administration, U.S. Department of Transportation, 2005. Table A.11. Technical Summary for Diamond Grinding and Grooving T re at m en t D es cr ip ti o n C o nd it io ns A d d re ss ed Structural: Diamond grinding and diamond grooving do not provide any structural benefit to the existing pavement, nor do they address or correct the mechanisms of the pavement distress. However, diamond grinding does reduce dynamic loading effects by removing faulting and improving the overall smoothness of the pavement, which is linked to extended pavement life. Noise: Diamond grinding is the most effective means of mitigating tire-pavement noise on existing concrete pavements. Diamond grooving may also reduce tire-pavement noise if done longitudinally. C o ns tr uc ti o n C o ns id er at io ns O th er R em ar ks A d d it io na l R es o ur ce s M is c e lla n e o u s C o n si d e ra ti o n s Treatment Life (yr): • Diamond grinding: 8 to 15 • Diamond grooving: 10 to 15 Pavement Life Extension (yr): • Diamond grinding: NA • Diamond grooving: NA

44Partial-Depth Repair Partial-depth repairs address small, shallow areas of deteriorated PCC pavements. These deteriorated areas are removed and replaced with an approved repair material, thereby maintaining the serviceability of the pavement. Partial-depth repairs should be used to correct joint spalling and other surface distresses that are limited to the upper third of the slab. Functional/Other • Joint spalling caused by non- materials-related sources, such as incompressible materials or joint inserts • Localized crazing or scaling caused by weak concrete or clay balls • It is important to properly determine repair boundaries, prepare the patch area, and finish, texture, and cure the repair material according to governing specifications. • Material selection depends on various factors, such as opening requirements, ambient temperature, cost, and size and depth of patch. • Proper and adequate preparation of the area to be patched is critical to ensure treatment success. The patch limits should extend 2 to 6 in. beyond the area of unsound concrete. • Minimum spall repair dimensions are 4 by 12 in. (i.e., 12 in. along a transverse joint and 4 in. away from the transverse joint). • Vertical faces are necessary when patching with most cementitious repair materials. Certain proprietary repair materials may be capable of successfully patching tapered sections. • After concrete removal, the repair area should be prepared by sandblasting or waterblasting, and airblasted clean immediately prior to the placement of the repair material. • When specified, bonding agents (e.g., portland cement grout or epoxy resin) should be appropriate for the time available before opening to traffic, and they should be compatible with concrete pavement. • Inserting a compressible bond breaker prevents intrusion of the patch material into the joint, which could result in premature compressive failure of the repair. • If the depth of the repair exceeds one-third of the slab thickness, then the placement of a full-depth repair should be considered. • Small milling machines (oriented either parallel or perpendicular to the joint) have been effectively used for concrete removal when spalling exists along the entire length of a joint. • Commercial rapid setting patch materials can allow for quick opening to traffic. Cost (Relative Cost, $ to $$$$): • $75 to $150/yd2 (patched area) ($$/$$$) • Safety: Safety can be improved by repairing severe spalls, which can cause vehicle damage due to loose debris. • Risk: Performance failures are often caused by the following: bond failure, compression failure, variability and improper use of repair material, insufficient consolidation, and differences of the coefficient of thermal expansion between the existing pavement and patch. • Climate: PCC patches should not be placed when the air temperature or pavement temperature is below 40°F, unless adequately insulated. Furthermore, temperatures below 55°F will usually require a longer cure period. Placement should not proceed if rain is imminent. • Not applicable where spalling caused by dowel bar misalignment or lockup; cracking caused by improper joint construction; working cracks caused by shrinkage, fatigue, or foundation movement; and spalling caused by materials-related distress (e.g., D-cracking or alkali- silica reactivity). • Full-depth repair is necessary if dowel bars or tie bars are exposed in the patch area. • Where the amount of patching is extensive, an overlay should be considered. • Manual of Practice: Materials and Procedures for Rapid Repair of Partial-Depth Spalls in Concrete Pavements. Report FHWA-RD-99- 152. Federal Highway Administration, U.S. Department of Transportation, 1999. • Smith, K. D., T. E. Hoerner, and D. G. Peshkin. Concrete Pavement Preservation Workshop—Reference Manual. Federal Highway Administration, U.S. Department of Transportation, 2008. • Pavement Preservation Checklist Series: 9. Partial-Depth Repair of PCC Pavements. Publication FHWA-IF-03-042. Federal Highway Administration, U.S. Department of Transportation, 2005. Table A.12. Technical Summary for Partial-Depth Repair T re at m en t D es cr ip ti o n C o nd it io ns A d d re ss ed Structural: Partial-depth repairs restore the structural integrity of localized areas of deteriorated concrete. Noise: Partial-depth repairs may result in increased roughness if not finished properly. Diamond grinding is generally recommended to blend the repaired surface with the surrounding pavement. C o ns tr uc ti o n C o ns id er at io ns O th er R em ar ks A d d it io na l R es o ur ce s M is c e lla n e o u s C o n si d e ra ti o n s Treatment Life (yr): • 5 to 15 Pavement Life Extension (yr): • NA

45Full-Depth Repair Full-depth repairs are cast-in-place or precast concrete repairs that extend through the full thickness of the existing slab, requiring full- depth removal and replacement of full lane-width areas. Full-depth repairs are effective at correcting slab distresses that extend beyond one-third the pavement depth, such as longitudinal and transverse cracking, corner breaks, and deep joint spalling. Functional/Other • Longitudinal cracking • Transverse cracking • Divided slab • Corner breaks • Joint spalling • Punchouts • Blowups • D-cracking or ASR distress* • It is important to properly prepare the base, restore joint load transfer, and finish, texture, and cure the patch material per governing specifications. Proper curing is even more important when incorporating set accelerating mix components. • Material selection depends on various factors but is largely a function of the opening requirements of the repair. • Proper and adequate preparation of the area to be patched is critical to ensure treatment success. The patch limits should extend 2 to 6 in. beyond the area of unsound concrete. • Repair boundaries should be sawed full-depth with diamond saw blades. To prevent subbase damage, the saw must not penetrate more than 0.5 in. into the subbase. • To expedite construction, contractors often make all of the required full-depth saw cuts before initiating slab removal activities. When this is done, it is important to limit (no more than 2 days typically) traffic loading between the time of sawing and concrete removal to avoid pumping and erosion beneath the slab. • Minimum repair dimensions: 6 ft long and 12 ft wide (full lane width) • Effective load transfer is critical to performance. Typically, 1.5-in.-diameter dowels, with either three to five bars clustered in the wheel path or placed continuously across the joint on 12-in. centers. • The lift-out method of removing deteriorated concrete from the repair area is recommended so as to minimize disturbance to the base, as well as generally providing the best results and highest productivity for comparable cost. • Replacing damaged subbase or subgrade materials with concrete is recommended to prevent settlement of the repair, as it is very difficult to adequately compact granular material in a confined area. • Transverse and longitudinal repair joints should be sealed so as to reduce spalling and to minimize infiltration of moisture and incompressible materials. Cost (Relative Cost, $ to $$$$): • $75 to $150/yd2 (patched area) ($$/$$$) • Risk: Performance failures are often caused by the following: inadequate load transfer, poor base preparation, variability of repair material, insufficient consolidation, and differences of the coefficient of thermal expansion between the existing pavement and patch. • Climate: PCC patches should not be placed when the air temperature or pavement temperature is below 40°F, unless adequately insulated. Furthermore, temperatures below 55°F will usually require a longer cure period. Placement should not proceed if rain is imminent. • Not cost effective or desirable if deterioration is widespread. • Where the amount of slab cracking is extensive (say, more than 5% to 10% of the slabs are cracked), a structural overlay may be required. • Generally, half lane-width repairs are used only on continuously reinforced concrete pavements and are not recommended for jointed concrete pavements. • Smith, K. D., T. E. Hoerner, and D. G. Peshkin. Concrete Pavement Preservation Workshop—Reference Manual. Federal Highway Administration, U.S. Department of Transportation, 2008. • Pavement Preservation Checklist Series: 10. Full-Depth Repair of PCC Pavements. Publication FHWA-IF-03-043. Federal Highway Administration, U.S. Department of Transportation, 2005. *Can serve to temporarily treat materials-related distresses. Table A.13. Technical Summary for Full-Depth Repair T re at m en t D es cr ip ti o n C o nd it io ns A d d re ss ed Structural: Subgrade repairs may be addressed when installing a full-depth repair. Helps restore structural integrity but does not address any structural inadequacy in existing pavement. Noise: Additional joints introduced by full-depth repairs add to pavement roughness, which can increase tire-pavement noise. Diamond grinding should be considered after full-depth repairs are made. C o ns tr uc ti o n C o ns id er at io ns O th er R em ar ks A d d it io na l R es o ur ce s M is c e lla n e o u s C o n si d e ra ti o n s Treatment Life (yr): • 5 to 15 Pavement Life Extension (yr): • NA

46Load Transfer Restoration (Dowel Bar Retrofitting) Load transfer restoration (LTR) consists of placing mechanical load transfer devices (typically dowel bars) across joints or cracks in an existing jointed PCC pavement. These devices increase the load transfer capacity of the joint or crack, thereby reducing deflections and decreasing the potential for the development of pumping, faulting, and corner breaks. Poor load transfer at existing joints or cracks may result from an undoweled jointing situation (in which excessive joint or crack openings leads to reduced aggregate interlock), corrosion of existing load transfer devices, and poor pavement drainage resulting in loss of underlying support. Functional/Other • Joint faulting • Pumping • Corner breaks • There are different patterns for placing dowel bars in a load transfer restoration project, but the use of three or four dowel bars clustered in each wheel path is typical. • Careful consideration must be given to selecting patch material and isolating the joint for repair. • Special diamond slot cutters capable of creating multiple cuts in a single operation should be employed for highest productivity. Slots created with milling machines typically cause excessive spalling on the surface and do not create uniform slot widths. • Dowel bar slots should be sawed to a depth sufficient to place the center of the dowel bar within 1 in. of the mid-depth of the pave- ment, and they should be aligned to avoid existing longitudinal cracks. Additionally, slots should be centered over the transverse joint or crack, allowing equal lengths of the dowel to span it, and slots should be parallel to the roadway’s centerline, regardless of joint skew. • Transverse joints/cracks should be maintained with a compressible insert. The transverse joint or crack should be caulked sufficiently to prevent any of the patching material from entering the joint/crack. • The chairs should be strong enough to allow full support of the dowel bar, as well as allowing ≥0.5-in. clearance between the bottom of the dowel and the bottom of the slot. • End caps should allow ≥0.25 in. of movement at each end of the dowel bar. • Patching material should be placed in a manner that does not disturb the dowel bar within the slot; thus, patching material should not be dumped into the slots, instead should be placed on the surface adjacent to the slot and shoved into the slot. Cost (Relative Cost, $ to $$$$): • $25 to $35/bar (equivalent $3.75 to $5.25/yd2, based on 6 bars per 12-ft crack/joint and crack/joint retrofits every 30 ft) ($$$) • Risk: The alignment of dowel bar slots must be parallel to the roadway centerline, regardless of transverse joint skew; slots perpen- dicular to skewed joints will cause joint lockup and lead to cracking. Additionally, slots sawed too deeply will contribute to corner cracks under traffic loading. • Climate: PCC patches should not be placed when the air temperature or pavement temperature is below 40°F, unless adequately insulated. Furthermore, temperatures below 55°F will usually require a longer cure period. • Most effective to apply treatment as structural distresses (e.g., pumping or corner breaks) are just beginning to manifest. Generally want less than 10% slab cracking and faulting of no more than 0.5 in. • The higher the traffic volume and percentage of trucks, the greater the potential need for load transfer restoration; low-traffic-volume roadways that are not doweled may not need such treatment. • Diamond grinding should be done in conjunction with load transfer restoration to ensure a smooth riding surface. • Smith, K. D., T. E. Hoerner, and D. G. Peshkin. Concrete Pavement Preservation Workshop—Reference Manual. Federal Highway Administration, U.S. Department of Transportation, 2008. • Pavement Preservation Checklist Series: 8. Dowel Bar Retrofit for Portland Cement Concrete Pavements. Publication FHWA-IF-03- 041. Federal Highway Administration, U.S. Department of Transportation, 2005. Table A.14. Technical Summary for Load-Transfer Restoration T re a tm e n t D e sc ri p ti o n C o n d it io n s A d d re ss e d Structural: The load transfer efficiency of a joint or crack strongly influences the structural performance of a PCC pavement; poor load transfer can result in pumping, faulting, corner breaks, and spalling. Noise: LTR is often performed in conjunction with diamond grinding, which reduces tire- pavement noise. C o n st ru c ti o n C o n si d e ra ti o n s M is c e lla n e o u s C o n si d e ra ti o n s Treatment Life (yr): • 10 to 15 Pavement Life Extension (yr): • NA O th e r R e m a rk s A d d it io n a l R e so u rc e s