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Page 85
Suggested Citation:"Glossary." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
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Suggested Citation:"Glossary." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
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Suggested Citation:"Glossary." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
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Suggested Citation:"Glossary." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
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Suggested Citation:"Glossary." National Academies of Sciences, Engineering, and Medicine. 2011. Preservation Approaches for High-Traffic-Volume Roadways. Washington, DC: The National Academies Press. doi: 10.17226/14508.
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Page 89

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88 AADT. The average annual daily traffic, expressed as the 24-hour traffic volume counts collected over a number of days greater than 1 but less than a year, at a given location. AADT can also be approximated by adjusting the ADT count for daily (weekday versus weekend) and seasonal (summer versus winter) variations. AADTT. The average annual daily truck traffic, expressed as the 24-hour truck traffic volume counts collected over a number of days greater than 1 but less than a year, at a given location. ADTT may be expressed as a percentage of ADT. ADT. The average daily traffic, expressed as the 24-hour traf- fic volume counts collected over a number of days greater than 1 but less than a year, at a given location. alligator cracking. Cracking of a hot-mix asphalt (HMA) roadway surface caused by fatigue failure of the HMA sur- face under repeated traffic loading. The cracks form many- sided, sharp-angled pieces that develop a pattern similar to the skin of an alligator. alternatives. Available choices or courses of action (e.g., alternative pavement types or rehabilitation or preserva- tion treatment types) that can be considered at each stage of resource allocation or utilization. asphalt cement. A bituminous material often used as a binder with aggregate to form a cold- or hot-applied paving material. asphalt concrete. See hot-mix asphalt. asphalt emulsion. A mixture of asphalt cement, water, and an emulsifying agent used in pavement construction and maintenance. base. The layer of material immediately beneath the pave- ment surface or binder course. benefit-cost. A comparison analysis of the economic benefit of an investment to its cost. The benefit-cost analysis should include all costs and benefits to both the agency and the users of the facility over an appropriate life-cycle period. In asset management, benefit-cost can be applied for prioritizing projects, evaluation of the benefits and costs for all projects in a program, and determination of program trade-offs. binder. An adhesive composition of asphalt cement, modified asphalt cement, or other bituminous materials, which is pri- marily responsible for binding aggregate particles together. Also used to refer to the layer of HMA directly below the surface course (i.e., binder course). block cracking. Cracking of a roadway surface caused by shrinkage of the asphalt concrete and daily temperature cycling, usually developing in a block-shaped pattern. cape seal. A surface treatment that involves the application of a slurry seal to a newly constructed chip seal. Cape seals are used to provide a dense, waterproof surface with improved skid resistance. chip seal. A surface treatment in which a pavement surface is sprayed with asphalt (generally emulsified) and then immediately covered with aggregate and rolled. Chip seals are used primarily to seal the surface of a pavement with non-load-associated cracks and to improve surface fric- tion (skid resistance). Also referred to as seal coat. cold in-place recycling (CIR). A process in which a portion of an existing bituminous pavement is pulverized or milled, the reclaimed material is mixed with new binder and new materials, and the resultant blend is placed as a base for a subsequent overlay. cold milling. A process of removing pavement material from the surface of the pavement either to prepare the surface to receive overlays (by removing rutting and sur- face irregularities), to restore pavement cross slopes and profile, or to reestablish the pavement’s surface friction characteristics. condition. Measure of the physical state of an asset as affected by deterioration and past maintenance and repair. condition index. A numeric score determined from pavement condition data and used to represent the performance of the pavement. Glossary

corrective maintenance. Maintenance activities performed in response to the development of a deficiency or deficien- cies that negatively affect the safe, efficient operations of a facility and future integrity of pavement sections. Correc- tive maintenance (sometimes referred to as reactionary maintenance) is usually performed to fix a localized defect or defects that arise from unforeseen conditions and restore a pavement to an acceptable level of service. crack filling. A maintenance procedure that involves place- ment of materials into nonworking cracks to substantially reduce infiltration of water and to reinforce the adjacent pavement. Nonworking cracks are defined as those that experience horizontal movements less than about 2 mm (0.1 in.). crack sealing. A maintenance procedure that involves place- ment of specialized materials, either above or into working cracks, using unique configurations to reduce the intrusion of incompressibles into the crack and to prevent intrusion of water into the underlying pavement layers. Working cracks are defined as those that experience horizontal move- ments greater than about 2 mm (0.1 in.). diamond grinding. A maintenance procedure for PCC pavements that involves the removal of a thin layer of PCC (generally no more than 6.4 mm [0.25 in.]) from the sur- face of a pavement to remove surface irregularities (most commonly joint faulting), to restore a smooth riding sur- face, and to increase pavement surface friction. diamond grooving. The establishment of discrete grooves in the concrete pavement surface using diamond saw blades to provide a drainage channel for water and thereby reduce the potential for hydroplaning and wet weather accidents. dowel bar retrofit (DBR). See load transfer restoration (LTR). equivalent single-axle load (ESAL). A concept that equates the damage to a pavement structure caused by the passage of a nonstandard axle load to a standard 80-kN (18-kip) axle load, in terms of calculated or measured stress, strain, or deflection at some point in the pavement structure, or in terms of equal conditions of distress or loss of serviceability. fatigue cracking. Cracking of a roadway surface caused by repetitive loading. Fatigue cracking often begins as a sin- gle crack in the wheelpath, develops into parallel cracks, and then continues as interconnected cracks. Also referred to as alligator cracking. faulting. Differential vertical displacement of abutting PCC pavement slabs at joints or cracks, creating a steplike defor- mation in the pavement. flexible pavement. A pavement structure composed of an asphalt concrete (AC) surface (usually HMA) and an aggre- gate or stabilized base/subbase. fog seal. A light application of slow-setting asphalt emulsion diluted with water that is used on HMA pavements or chip seals. full-depth repair. Cast-in-place concrete repairs that extend the full depth of the existing slab. The technique involves the full-depth removal and replacement of full- or half-lane- width areas of an existing deteriorated PCC pavement. functional distress. Deterioration that affects the ability of the pavement to provide a safe, smooth, and quiet surface for driving. Most functional problems can be corrected with preservation treatments if there is no serious under- lying structural problem. high-traffic-volume roadway. As defined in this study, a rural roadway with ADT greater than 5,000 vpd, or an urban roadway with ADT greater than 10,000 vpd. hot in-place recycling (HIR). A process that involves soft- ening an existing bituminous surface with heat, mechani- cally removing the surface material, mixing the material with a recycling agent, adding new asphalt or aggregate to the material (if required), and then replacing the material back on the roadway. There are three types of HIR: surface recycling, remixing, and repaving. hot-mix asphalt (HMA). A plant-produced, high-quality hot mixture of asphalt cement and well-graded, high-quality aggregate thoroughly compacted into a uniform dense mass. international roughness index (IRI). A measurement of the roughness of a pavement, expressed as the ratio of the accumulated suspension motion to the distance traveled. It is obtained from a mathematical model of a standard quarter car traversing a measured profile at a speed of 80 km/h (50 mph). joint resealing. The resealing of transverse joints in PCC pavements to minimize the infiltration of surface water into the underlying pavement structure and to prevent the intrusion of incompressibles into the joint. life cycle. A length of time that spans the stages of asset construction, operation, maintenance, rehabilitation, and reconstruction or disposal or abandonment; when associ- ated with analyses, refers to a length of time sufficient to span these several stages and to capture the costs, benefits, and long-term performance impacts of different investment options. life-cycle cost analysis (LCCA). A method of reducing all of the significant costs of an asset over its lifetime to either a present worth (today’s cost) or an equivalent uniform annual cost (annual cost). As such, LCCA accounts for initial (or in-place) costs, subsequent maintenance and rehabilitation costs, and salvage value. In addition to all of these costs, inputs to an LCCA include the analysis period and the discount rate (reflecting the time value of money). load transfer restoration (LTR). The placement of load transfer devices, such as dowel bars, across joints or cracks in an existing jointed PCC pavement. 89

longitudinal cracking. Cracking in a pavement surface that is oriented parallel to the direction of travel. major rehabilitation. Structural enhancements that extend the service life of an existing pavement or improve its load- carrying capability. microsurfacing. A mixture of polymer-modified asphalt emulsion, mineral aggregate, mineral filler, water, and other additives, properly proportioned, mixed, and spread on a pavement (usually bituminous) surface. minor rehabilitation. Nonstructural enhancements (e.g., thin HMA overlay, mill and thin HMA overlay) made to an exist- ing pavement section to either eliminate age-related, top- down surface cracking that develops in flexible pavements due to environmental exposure, or to restore functionality of concrete pavements. Because of the nonstructural nature of minor rehabilitation techniques, they are placed in the cat- egory of pavement preservation. open-graded friction course (OGFC). A bituminous paving layer consisting of a mix of asphalt cement and open-graded (also called uniformly graded) aggregate. An open-graded aggregate consists of particles of predominantly a single-size aggregate. oxidation. Chemical reaction between the asphalt in an HMA pavement and air, causing the bituminous surface to become discolored and stiffer. partial-depth repairs. Removal of small, shallow areas of deteriorated PCC and replacement with a suitable repair material. It cannot accommodate the movements of work- ing joints and cracks, load transfer devices, or reinforcing steel without experiencing high stresses and material damage. pavement condition index (PCI). A condition index with a scale of 0 to 100, where 0 represents a failed pavement and 100 represents a pavement that is in excellent condition. See American Society for Testing and Material Standard D6433, Standard Practice for Roads and Parking Lots Pave- ment Condition Index Surveys. pavement friction. The retarding force developed at the tire–pavement interface that resists sliding when braking forces are applied to the vehicle tires. pavement maintenance. Work that is planned and per- formed on a routine basis to maintain and preserve the condition of the highway system or to respond to specific conditions and events that restore the highway system to an adequate level of service. pavement management. All the activities involved in the planning, programming, design, construction, mainte- nance, and rehabilitation of the pavement portion of a pub- lic works program. A system that involves the identification of optimum strategies at various management levels and maintains pavements at an adequate level of serviceability. These include, but are not limited to, systematic procedures for scheduling maintenance and rehabilitation activities based on optimization of benefits and minimization of costs. pavement management system (PMS). A set of tools or methods that assists decision makers in finding optimum strategies for providing, evaluating, and maintaining pave- ments in a serviceable condition over a period of time. pavement performance. The condition or serviceability of a pavement, either over time or at a given point in time. pavement preservation. A network-level, long-term strategy that enhances pavement performance by using an inte- grated, cost-effective set of practices to extend pavement life, improve safety, and meet motorist expectations. Pave- ment preservation programs normally include a combina- tion of preventive maintenance, minor rehabilitation, and routine maintenance work. However, the majority of work under typical pavement preservation programs is focused on preventive maintenance. pavement preventive maintenance. A planned strategy of cost-effective treatments to an existing roadway system and its appurtenances that preserves the system, retards future deterioration, maintains or improves the functional condition of the system, and extends the life of the exist- ing pavement (without increasing the structural capacity). pavement reconstruction. The replacement of an entire pavement structure with an equivalent or better pavement structure. Reconstruction usually requires the complete removal and replacement of the existing pavement struc- ture. Reconstruction may incorporate either new or recy- cled materials into the materials used for the reconstruction of the complete pavement section. Reconstruction is required when a pavement has either failed or has become functionally obsolete. pavement rehabilitation. Structural enhancements that extend the service life of an existing pavement or improve its load-carrying capacity. Rehabilitation techniques include restoration treatments and structural overlays. pavement texture. The characteristics of the pavement sur- face that contribute to both surface fiction and noise. Sur- face texture consists of microtexture and macrotexture. performance measure. An indicator, preferably quantita- tive, of service provided by the transportation system to users; the service may be gauged in several ways (e.g., qual- ity of ride, efficiency and safety of traffic movements, ser- vices at rest areas, quality of system condition). performance period. Length of time a pavement is expected to provide a minimum level of serviceability before major rehabilitation is required. performance target. Threshold value of a performance measure. 90

preoverlay repair. Improvements performed on an existing pavement prior to the placement of an overlay. present serviceability index (PSI). A subjective rating of the pavement condition made by a group of individuals riding over the pavement, ranging from 0 (impassable) to 5 (perfect). punchout. A major structural distress in continuously re- inforced concrete pavement (CRCP) caused by loss of materials under the slab and loss of aggregate interlock at one or two closely spaced cracks. raveling. The wearing away of a bituminous pavement sur- face caused by the dislodging of aggregate particles and loss of asphalt binder. remaining service life (RSL). The number of years before a pavement reaches an unacceptable serviceability level. rigid pavement. A pavement structure composed of a port- land cement concrete (PCC) surface and an aggregate or stabilized base. roughness. Distortions of the road surface that contribute to an undesirable, unsafe, uneconomical, or uncomfortable ride. routine maintenance. Planned work that is performed on a routine basis to maintain and preserve the condition of the highway system or respond to specific conditions and events that restore the highway system to an adequate level of service. rubberized asphalt chip seal. A variation on conventional chip seals in which the asphalt emulsion is replaced with a blend of ground tire rubber (or latex rubber) and asphalt cement to enhance the elasticity and adhesion characteris- tics of the binder. Aggregate is typically precoated and hot applied. rutting. A surface depression in the wheelpath caused by a permanent deformation in any of the pavement layers or subgrade. sand seal. An application of asphalt emulsion covered with fine aggregate. It may be used to improve the skid resistance of slippery pavements and to seal against air and water intrusion. sandwich seal. A surface treatment that consists of application of a large aggregate, followed by a spray of asphalt emulsion that is in turn covered with an application of smaller aggre- gate. Sandwich seals are used to seal the pavement surface and to improve skid resistance. scrub seal. The application of a polymer-modified asphalt emulsion to the bituminous surface, followed by the broom- scrubbing of the emulsion into cracks and voids, followed by the application of an even coat of sand or small aggregate, and finally a second brooming of the aggregate and asphalt mixture. This seal is then rolled with a pneumatic tire roller. serviceability. The ability of a pavement to serve the purpose for which it was designed and constructed. skid resistance. See pavement friction. slurry seal. A mixture of quick- or slow-setting emulsified asphalt, well-graded fine aggregate, mineral filler, and water. It is used to fill cracks and seal areas of bituminous pavements, to restore a uniform surface texture, to seal the surface to prevent moisture and air intrusion into the pave- ment, and to provide skid resistance. spalling. The breakdown of the slab edges within 2 ft (0.6 m) of the side of the joint caused by excessive stresses at the joint or crack or poor joint forming or sawing practices. stone matrix asphalt (SMA). A hot-mix asphalt consisting of a mix of asphalt cement, stabilizer material, mineral filler, and gap-graded aggregate. A gap-graded aggregate is simi- lar to an open-graded material but is not quite as open. structural distress. Deterioration caused by excessive load- ing, insufficient thickness, or lack of structural support. Pavements with considerable structural distress are not good candidates for preservation treatments. subbase. Layer of material in a pavement structure immedi- ately beneath the base course. subgrade soil. The native soil prepared and compacted to support a pavement structure. thin HMA overlays. Plant-mixed combinations of asphalt cement and aggregate that are commonly placed in thick- nesses between about 19 and 38 mm (0.75 and 1.50 in.). transverse cracking. Cracking in a pavement surface that is oriented perpendicular to the direction of travel. treatment category. A group of treatments with similar overall objectives and applied at similar times. For exam- ple, preventive maintenance treatments are intended to preserve pavement integrity and prevent or retard future pavement deterioration. treatment type. A specific work activity performed on a road- way pavement that is intended to treat one or more of the pavement’s deficiencies. Examples include crack sealing, thin HMA overlay applications, and diamond grinding. ultra-thin bonded wearing course. A preservation treatment for flexible pavements consisting of a layer of gap-graded, polymer-modified hot-mix asphalt (HMA) material placed over a heavy, polymer-modified emulsified asphalt tack coat. Sometimes called ultra-thin friction course. ultra-thin whitetopping (UTW). Thin PCC overlays of existing HMA pavements that consist of very thin (50 to 100 mm [2 to 4 in.]) layers of PCC bonded to an existing HMA pavement. undersealing. Also called subsealing, pressure grouting, or slab stabilization, this process consists of the pressure insertion of a flowable material used to fill voids beneath PCC slabs. 91

user benefits. Economic gains to transportation users resulting from a project or investment strategy. It may include monetary value of travel time savings, accident reductions, reduced vehicle operating costs, and savings or advantages gained from more reliable transportation services. user costs. Costs incurred by highway users traveling on the facility and the excess costs incurred by those who cannot use the facility because of either agency or self-imposed detour requirements. User costs are typically composed of vehicle operating costs, crash costs, and user delay costs. weathering. The hardening and aging of the asphalt binder. 92

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

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

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

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