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Glossary AADT. The average annual daily traffic, expressed as the for prioritizing projects, evaluation of the benefits and 24-hour traffic volume counts collected over a number of costs for all projects in a program, and determination of days greater than 1 but less than a year, at a given location. program trade-offs. AADT can also be approximated by adjusting the ADT binder. An adhesive composition of asphalt cement, modified count for daily (weekday versus weekend) and seasonal asphalt cement, or other bituminous materials, which is pri- (summer versus winter) variations. marily responsible for binding aggregate particles together. AADTT. The average annual daily truck traffic, expressed Also used to refer to the layer of HMA directly below the as the 24-hour truck traffic volume counts collected over surface course (i.e., binder course). a number of days greater than 1 but less than a year, at a block cracking. Cracking of a roadway surface caused by given location. ADTT may be expressed as a percentage shrinkage of the asphalt concrete and daily temperature of ADT. cycling, usually developing in a block-shaped pattern. ADT. The average daily traffic, expressed as the 24-hour traf- cape seal. A surface treatment that involves the application of fic volume counts collected over a number of days greater a slurry seal to a newly constructed chip seal. Cape seals are than 1 but less than a year, at a given location. used to provide a dense, waterproof surface with improved alligator cracking. Cracking of a hot-mix asphalt (HMA) skid resistance. roadway surface caused by fatigue failure of the HMA sur- chip seal. A surface treatment in which a pavement surface face under repeated traffic loading. The cracks form many- is sprayed with asphalt (generally emulsified) and then sided, sharp-angled pieces that develop a pattern similar to immediately covered with aggregate and rolled. Chip seals the skin of an alligator. are used primarily to seal the surface of a pavement with alternatives. Available choices or courses of action (e.g., non-load-associated cracks and to improve surface fric- alternative pavement types or rehabilitation or preserva- tion (skid resistance). Also referred to as seal coat. tion treatment types) that can be considered at each stage cold in-place recycling (CIR). A process in which a portion of resource allocation or utilization. of an existing bituminous pavement is pulverized or milled, asphalt cement. A bituminous material often used as a binder the reclaimed material is mixed with new binder and new with aggregate to form a cold- or hot-applied paving materials, and the resultant blend is placed as a base for a material. subsequent overlay. asphalt concrete. See hot-mix asphalt. cold milling. A process of removing pavement material asphalt emulsion. A mixture of asphalt cement, water, and from the surface of the pavement either to prepare the an emulsifying agent used in pavement construction and surface to receive overlays (by removing rutting and sur- maintenance. face irregularities), to restore pavement cross slopes and base. The layer of material immediately beneath the pave- profile, or to reestablish the pavement's surface friction ment surface or binder course. characteristics. benefit-cost. A comparison analysis of the economic benefit condition. Measure of the physical state of an asset as of an investment to its cost. The benefit-cost analysis affected by deterioration and past maintenance and repair. should include all costs and benefits to both the agency condition index. A numeric score determined from pavement and the users of the facility over an appropriate life-cycle condition data and used to represent the performance of the period. In asset management, benefit-cost can be applied pavement. 88
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89 corrective maintenance. Maintenance activities performed full-depth repair. Cast-in-place concrete repairs that extend in response to the development of a deficiency or deficien- the full depth of the existing slab. The technique involves the cies that negatively affect the safe, efficient operations of a full-depth removal and replacement of full- or half-lane- facility and future integrity of pavement sections. Correc- width areas of an existing deteriorated PCC pavement. tive maintenance (sometimes referred to as reactionary functional distress. Deterioration that affects the ability of maintenance) is usually performed to fix a localized defect the pavement to provide a safe, smooth, and quiet surface or defects that arise from unforeseen conditions and restore for driving. Most functional problems can be corrected a pavement to an acceptable level of service. with preservation treatments if there is no serious under- crack filling. A maintenance procedure that involves place- lying structural problem. ment of materials into nonworking cracks to substantially high-traffic-volume roadway. As defined in this study, a reduce infiltration of water and to reinforce the adjacent rural roadway with ADT greater than 5,000 vpd, or an pavement. Nonworking cracks are defined as those that urban roadway with ADT greater than 10,000 vpd. experience horizontal movements less than about 2 mm hot in-place recycling (HIR). A process that involves soft- (0.1 in.). ening an existing bituminous surface with heat, mechani- crack sealing. A maintenance procedure that involves place- cally removing the surface material, mixing the material ment of specialized materials, either above or into working with a recycling agent, adding new asphalt or aggregate to cracks, using unique configurations to reduce the intrusion the material (if required), and then replacing the material of incompressibles into the crack and to prevent intrusion back on the roadway. There are three types of HIR: surface of water into the underlying pavement layers. Working recycling, remixing, and repaving. cracks are defined as those that experience horizontal move- hot-mix asphalt (HMA). A plant-produced, high-quality hot ments greater than about 2 mm (0.1 in.). mixture of asphalt cement and well-graded, high-quality diamond grinding. A maintenance procedure for PCC aggregate thoroughly compacted into a uniform dense pavements that involves the removal of a thin layer of PCC mass. (generally no more than 6.4 mm [0.25 in.]) from the sur- international roughness index (IRI). A measurement of face of a pavement to remove surface irregularities (most the roughness of a pavement, expressed as the ratio of the commonly joint faulting), to restore a smooth riding sur- accumulated suspension motion to the distance traveled. face, and to increase pavement surface friction. It is obtained from a mathematical model of a standard diamond grooving. The establishment of discrete grooves in quarter car traversing a measured profile at a speed of the concrete pavement surface using diamond saw blades 80 km/h (50 mph). to provide a drainage channel for water and thereby reduce joint resealing. The resealing of transverse joints in PCC the potential for hydroplaning and wet weather accidents. pavements to minimize the infiltration of surface water dowel bar retrofit (DBR). See load transfer restoration (LTR). into the underlying pavement structure and to prevent equivalent single-axle load (ESAL). A concept that equates the intrusion of incompressibles into the joint. the damage to a pavement structure caused by the passage life cycle. A length of time that spans the stages of asset of a nonstandard axle load to a standard 80-kN (18-kip) axle construction, operation, maintenance, rehabilitation, and load, in terms of calculated or measured stress, strain, or reconstruction or disposal or abandonment; when associ- deflection at some point in the pavement structure, or in ated with analyses, refers to a length of time sufficient to span terms of equal conditions of distress or loss of serviceability. these several stages and to capture the costs, benefits, and fatigue cracking. Cracking of a roadway surface caused by long-term performance impacts of different investment repetitive loading. Fatigue cracking often begins as a sin- options. gle crack in the wheelpath, develops into parallel cracks, life-cycle cost analysis (LCCA). A method of reducing all of and then continues as interconnected cracks. Also referred the significant costs of an asset over its lifetime to either a to as alligator cracking. present worth (today's cost) or an equivalent uniform faulting. Differential vertical displacement of abutting PCC annual cost (annual cost). As such, LCCA accounts for pavement slabs at joints or cracks, creating a steplike defor- initial (or in-place) costs, subsequent maintenance and mation in the pavement. rehabilitation costs, and salvage value. In addition to all flexible pavement. A pavement structure composed of an of these costs, inputs to an LCCA include the analysis asphalt concrete (AC) surface (usually HMA) and an aggre- period and the discount rate (reflecting the time value of gate or stabilized base/subbase. money). fog seal. A light application of slow-setting asphalt emulsion load transfer restoration (LTR). The placement of load diluted with water that is used on HMA pavements or chip transfer devices, such as dowel bars, across joints or cracks seals. in an existing jointed PCC pavement.
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90 longitudinal cracking. Cracking in a pavement surface that These include, but are not limited to, systematic procedures is oriented parallel to the direction of travel. for scheduling maintenance and rehabilitation activities major rehabilitation. Structural enhancements that extend based on optimization of benefits and minimization of the service life of an existing pavement or improve its load- costs. carrying capability. pavement management system (PMS). A set of tools or microsurfacing. A mixture of polymer-modified asphalt methods that assists decision makers in finding optimum emulsion, mineral aggregate, mineral filler, water, and other strategies for providing, evaluating, and maintaining pave- additives, properly proportioned, mixed, and spread on a ments in a serviceable condition over a period of time. pavement (usually bituminous) surface. pavement performance. The condition or serviceability of a minor rehabilitation. Nonstructural enhancements (e.g., thin pavement, either over time or at a given point in time. HMA overlay, mill and thin HMA overlay) made to an exist- pavement preservation. A network-level, long-term strategy ing pavement section to either eliminate age-related, top- that enhances pavement performance by using an inte- down surface cracking that develops in flexible pavements grated, cost-effective set of practices to extend pavement due to environmental exposure, or to restore functionality life, improve safety, and meet motorist expectations. Pave- of concrete pavements. Because of the nonstructural nature ment preservation programs normally include a combina- of minor rehabilitation techniques, they are placed in the cat- tion of preventive maintenance, minor rehabilitation, and egory of pavement preservation. routine maintenance work. However, the majority of work open-graded friction course (OGFC). A bituminous paving under typical pavement preservation programs is focused layer consisting of a mix of asphalt cement and open-graded on preventive maintenance. (also called uniformly graded) aggregate. An open-graded pavement preventive maintenance. A planned strategy of aggregate consists of particles of predominantly a single-size cost-effective treatments to an existing roadway system aggregate. and its appurtenances that preserves the system, retards oxidation. Chemical reaction between the asphalt in an future deterioration, maintains or improves the functional HMA pavement and air, causing the bituminous surface condition of the system, and extends the life of the exist- to become discolored and stiffer. ing pavement (without increasing the structural capacity). partial-depth repairs. Removal of small, shallow areas of pavement reconstruction. The replacement of an entire deteriorated PCC and replacement with a suitable repair pavement structure with an equivalent or better pavement material. It cannot accommodate the movements of work- structure. Reconstruction usually requires the complete ing joints and cracks, load transfer devices, or reinforcing removal and replacement of the existing pavement struc- steel without experiencing high stresses and material ture. Reconstruction may incorporate either new or recy- damage. cled materials into the materials used for the reconstruction pavement condition index (PCI). A condition index with a of the complete pavement section. Reconstruction is scale of 0 to 100, where 0 represents a failed pavement and required when a pavement has either failed or has become 100 represents a pavement that is in excellent condition. functionally obsolete. See American Society for Testing and Material Standard pavement rehabilitation. Structural enhancements that D6433, Standard Practice for Roads and Parking Lots Pave- extend the service life of an existing pavement or improve ment Condition Index Surveys. its load-carrying capacity. Rehabilitation techniques include pavement friction. The retarding force developed at the restoration treatments and structural overlays. tirepavement interface that resists sliding when braking pavement texture. The characteristics of the pavement sur- forces are applied to the vehicle tires. face that contribute to both surface fiction and noise. Sur- pavement maintenance. Work that is planned and per- face texture consists of microtexture and macrotexture. formed on a routine basis to maintain and preserve the performance measure. An indicator, preferably quantita- condition of the highway system or to respond to specific tive, of service provided by the transportation system to conditions and events that restore the highway system to users; the service may be gauged in several ways (e.g., qual- an adequate level of service. ity of ride, efficiency and safety of traffic movements, ser- pavement management. All the activities involved in the vices at rest areas, quality of system condition). planning, programming, design, construction, mainte- performance period. Length of time a pavement is expected nance, and rehabilitation of the pavement portion of a pub- to provide a minimum level of serviceability before major lic works program. A system that involves the identification rehabilitation is required. of optimum strategies at various management levels and performance target. Threshold value of a performance maintains pavements at an adequate level of serviceability. measure.
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91 preoverlay repair. Improvements performed on an existing serviceability. The ability of a pavement to serve the purpose pavement prior to the placement of an overlay. for which it was designed and constructed. present serviceability index (PSI). A subjective rating of skid resistance. See pavement friction. the pavement condition made by a group of individuals slurry seal. A mixture of quick- or slow-setting emulsified riding over the pavement, ranging from 0 (impassable) to asphalt, well-graded fine aggregate, mineral filler, and 5 (perfect). water. It is used to fill cracks and seal areas of bituminous punchout. A major structural distress in continuously re- pavements, to restore a uniform surface texture, to seal the inforced concrete pavement (CRCP) caused by loss of surface to prevent moisture and air intrusion into the pave- materials under the slab and loss of aggregate interlock at ment, and to provide skid resistance. one or two closely spaced cracks. spalling. The breakdown of the slab edges within 2 ft (0.6 m) raveling. The wearing away of a bituminous pavement sur- of the side of the joint caused by excessive stresses at the face caused by the dislodging of aggregate particles and joint or crack or poor joint forming or sawing practices. loss of asphalt binder. stone matrix asphalt (SMA). A hot-mix asphalt consisting of remaining service life (RSL). The number of years before a a mix of asphalt cement, stabilizer material, mineral filler, pavement reaches an unacceptable serviceability level. and gap-graded aggregate. A gap-graded aggregate is simi- rigid pavement. A pavement structure composed of a port- lar to an open-graded material but is not quite as open. land cement concrete (PCC) surface and an aggregate or structural distress. Deterioration caused by excessive load- stabilized base. ing, insufficient thickness, or lack of structural support. roughness. Distortions of the road surface that contribute to Pavements with considerable structural distress are not an undesirable, unsafe, uneconomical, or uncomfortable good candidates for preservation treatments. ride. subbase. Layer of material in a pavement structure immedi- routine maintenance. Planned work that is performed on a ately beneath the base course. routine basis to maintain and preserve the condition of the subgrade soil. The native soil prepared and compacted to highway system or respond to specific conditions and support a pavement structure. events that restore the highway system to an adequate level thin HMA overlays. Plant-mixed combinations of asphalt of service. cement and aggregate that are commonly placed in thick- rubberized asphalt chip seal. A variation on conventional nesses between about 19 and 38 mm (0.75 and 1.50 in.). chip seals in which the asphalt emulsion is replaced with a transverse cracking. Cracking in a pavement surface that is blend of ground tire rubber (or latex rubber) and asphalt oriented perpendicular to the direction of travel. cement to enhance the elasticity and adhesion characteris- treatment category. A group of treatments with similar tics of the binder. Aggregate is typically precoated and hot overall objectives and applied at similar times. For exam- applied. ple, preventive maintenance treatments are intended to rutting. A surface depression in the wheelpath caused by a preserve pavement integrity and prevent or retard future permanent deformation in any of the pavement layers or pavement deterioration. subgrade. treatment type. A specific work activity performed on a road- sand seal. An application of asphalt emulsion covered with way pavement that is intended to treat one or more of the fine aggregate. It may be used to improve the skid resistance pavement's deficiencies. Examples include crack sealing, of slippery pavements and to seal against air and water thin HMA overlay applications, and diamond grinding. intrusion. ultra-thin bonded wearing course. A preservation treatment sandwich seal. A surface treatment that consists of application for flexible pavements consisting of a layer of gap-graded, of a large aggregate, followed by a spray of asphalt emulsion polymer-modified hot-mix asphalt (HMA) material placed that is in turn covered with an application of smaller aggre- over a heavy, polymer-modified emulsified asphalt tack gate. Sandwich seals are used to seal the pavement surface coat. Sometimes called ultra-thin friction course. and to improve skid resistance. ultra-thin whitetopping (UTW). Thin PCC overlays of scrub seal. The application of a polymer-modified asphalt existing HMA pavements that consist of very thin (50 to emulsion to the bituminous surface, followed by the broom- 100 mm [2 to 4 in.]) layers of PCC bonded to an existing scrubbing of the emulsion into cracks and voids, followed by HMA pavement. the application of an even coat of sand or small aggregate, undersealing. Also called subsealing, pressure grouting, or and finally a second brooming of the aggregate and asphalt slab stabilization, this process consists of the pressure mixture. This seal is then rolled with a pneumatic tire insertion of a flowable material used to fill voids beneath roller. PCC slabs.
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92 user benefits. Economic gains to transportation users user costs. Costs incurred by highway users traveling on the resulting from a project or investment strategy. It may facility and the excess costs incurred by those who cannot include monetary value of travel time savings, accident use the facility because of either agency or self-imposed reductions, reduced vehicle operating costs, and savings detour requirements. User costs are typically composed of or advantages gained from more reliable transportation vehicle operating costs, crash costs, and user delay costs. services. weathering. The hardening and aging of the asphalt binder.