| A |
|
| |
|
| Absolute Viscosity |
A measure of the viscosity of asphalt with respect to time, measured
in poises,
conducted at 60°C (140°F). The test method utilizes a partial vacuum to induce
flow
in the viscometer. |
| |
|
| Aggregate Spreaders |
Machines used for spreading aggregate evenly at a uniform rate on a surface. |
| |
|
| Aggregate Storage
Bins |
Bins that store the necessary aggregate sizes and feed them to the dryer
in
substantially the same proportions as are required in the finished mix. |
| |
|
| Aggregate Trucks |
Trucks equipped with hydraulic lifts to dump the aggregate into the spreader
or
storage area. |
| |
|
| Aggregate |
A hard inert mineral material, such as gravel, crushed rock, slag, or
crushed stone, used in pavement applications either by itself or for mixing
with asphalt. |
| |
|
| Air Voids |
Internal spaces in a compacted mix surrounded by asphalt-coated particles,
expressed as a percentage by volume of the total compacted mix. |
| |
|
Asphalt
(asphalt cement) |
A dark brown to black cementitious material in which the predominating
constituents are bitumens, which occur in nature or are obtained in petroleum
processing. Asphalt is a constituent in varying proportions of most crude
petroleum
and used for paving, roofing, industrial and other special purposes. |
| |
|
| Alligator Cracks |
Interconnected cracks forming a series of small blocks resembling an
alligator's skin or chicken-wire, and caused by excessive deflection of
the surface over unstable
subgrade or lower courses of the pavement. |
| |
|
| Asphalt
Application |
The application of sprayed asphalt coatings not involving the use of aggregates. |
| |
|
| Asphalt Binder |
Asphalt cement that is classified according to the Standard Specification
for Performance Graded Asphalt Binder, AASHTO Designation MP1. It can be
either
unmodified or modified asphalt cement, as long as it complies with the
specifications. |
| |
|
| Asphalt Concrete |
A mixture of asphalt binder and aggregate thoroughly mixed and compacted into
a
mass. |
| |
|
| Asphalt
Distributor |
A truck or a trailer having an insulated tank, heating system and distribution
system.
The distributor applies asphalt to a surface at a uniform rate. |
| |
|
| Asphalt Emulsion |
An emulsion of asphalt binder and water that contains a small amount
of an emulsifying agent. Emulsified asphalt droplets may be of either the
anionic (negative
charge), cationic (positive charge) or nonionic (neutral). |
| |
|
| Asphalt Emulsion Mix (Cold) |
A mixture of unheated mineral aggregate and emulsified (or cutback) asphalt
binder. It can be plant-mixed or mixed in-place. |
| |
|
| Asphalt Emulsion Mix (Warm) |
A mixture of asphalt emulsion and mineral aggregate usually prepared
in a conventional hot mix asphalt plant at a temperature less than
95°C (200°F). It is spread and compacted at a temperature above 65°C
(150°F). |
| |
|
| Asphalt Emulsion Slurry Seal |
A mixture of slow-setting emulsified asphalt, fine aggregate, and mineral
filler with a slurry consistency |
| |
|
| Asphalt Leveling Course |
A course of hot mix asphalt of variable thickness used to eliminate irregularities
in the contour of an existing surface prior to placing the
subsequent course. |
| |
|
| Asphalt Pavement Structure |
A pavement structure that is designed and constructed so that all courses above
the subgrade are asphalt concrete (Full-Depth Asphalt
Pavement) |
| |
|
| Asphalt Pavements |
Pavements consisting of a surface course of asphalt concrete over supporting
courses such as asphalt concrete bases, crushed stone, slag, gravel, Portland
Cement Concrete (PCC), brick, or block
pavement |
| |
|
| Asphalt Prime Coat |
An application of asphalt primer to an absorbent surface. It is used
to prepare an untreated base for an asphalt surface. The prime penetrates
or is mixed into the surface of the base and plugs the voids, hardens the
top and helps bind it to the overlying asphalt course. |
| |
|
| Asphalt Primer |
Low viscosity asphalt (highly liquid) that penetrates into a non-bituminous
surface
upon application |
| |
|
| Asphalt Rubber - Asphalt
Concrete (AR-AC) |
High quality, thoroughly controlled hot mixture of asphalt rubber binder
(AR) and well-graded, high quality aggregate, which can be thoroughly compacted
into a uniform dense mass. |
| |
|
| Asphalt Rubber Binder (AR) |
Conventional asphalt cement to which recycled ground tire rubber has
been added, that when reacted with the hot asphalt cement causes a swelling
and/or dispersion of the tire rubber particles |
| |
|
| Asphalt Tack Coat |
A relatively thin application of asphalt binder applied to an existing
asphalt concrete or PCC surface at a prescribed rate. Asphalt emulsion
diluted with water is the preferred type. It is used to form a bond between
an existing surface and the overlying course. |
| |
|
| Asphaltenes |
The high molecular weight hydrocarbon fraction precipitated from asphalt by a
designated paraffinic naphtha solvent at a specified
solvent-asphalt ratio. |
| |
|
Automatic Cycling
Control |
A control system in which the opening and closing of the weigh hopper
discharge gate, the bituminous discharge valve, and the pugmill discharge
gate are actuated by means of self-acting mechanical or electrical machinery
without any intermediate manual control. The system includes preset timing
devices to control the desired periods of dry and wet mixing cycles. |
| |
|
| Automatic Dryer
Control |
A system that automatically maintains the temperature of aggregates discharged
from the dryer within a preset range. |
| |
|
| Automatic Proportioning
Control |
A system in which proportions of the aggregate and asphalt fractions
are controlled by means of gates or valves, which are opened and closed
by means of self-acting mechanical or electronic machinery without any
intermediate manual control. |
| |
|
| |
 |
| B
|
|
| |
|
| Back-calculation |
An analytical technique used to determine the equivalent
elastic moduli of pavement layers corresponding to the measured load and
deflections. In the iterative method, layer moduli are selected and adjusted
until the difference between the calculated and measured deflections are
within selected tolerances, or the maximum number of iterations has been
reached. |
| |
|
| Bank Gravel |
Gravel found in natural deposits, usually intermixed with
fine material such as sand or clay or a combination thereof; includes
gravelly clay, gravelly sand, clayey gravel, and sandy gravel (the names
indicate the relative proportion of the materials in the mixture). |
| |
|
| Base Course |
The layer in the pavement system immediately below the
binder and surface courses. It usually consists of crushed stone, although
it may consist of crushed slag or other stabilized or unstabilized material. |
| |
|
| Batch Plant |
A manufacturing facility for producing asphalt paving mixtures
that proportions blending. They manufacture asphalt in batches rather
than continuously and are more suited for small manufacturing runs and
(frequent) changes in mixture types. |
| |
|
| Binder Course |
The hot mix asphalt course immediately below the surface
course, generally consisting of larger aggregates and less asphalt (by
weight) than the surface. |
| |
|
| Bitumen |
A class of black or dark-colored (solid, semisolid, or
viscous) cementitious substances, natural or manufactured, composed principally
of high molecular weight hydrocarbons, of which asphalts, tars, pitches,
and asphaltites are typical. |
| |
|
| Blast-Furnace Slag |
The nonmetallic product, consisting essentially of silicates
and alumino-silicates of lime and of other bases, that is developed simultaneously
with iron in a blast furnace. |
| |
|
| Bleeding or Flushing Asphalt |
The upward migration of asphalt binder in an asphalt pavement resulting in the
formation of asphalt film on the surface. |
| |
|
| C |
|
| |
|
| California Bearing Ratio (CBR) |
A test used for evaluating bases, subbases, and subgrades
for pavement thickness design it is a relative measure of the shear resistance
of a soil (see Soils Manual, MS-10). CBR = load required to force a calibrated
piston into a soil specimen / load required to force a like piston into
a crushed stone specimen capacity and ride quality of the pavement system. |
| |
|
| Cape Seal |
A surface treatment where a chip seal is followed by the
application of either slurry seal or micro-surfacing. |
| |
|
| Channels (Ruts) |
Channeled depressions that sometimes develop in the wheel
paths of an asphalt pavement. |
| |
|
| Clinker |
A fused or partially fused by-product of the combustion
of coal. Also includes lava and Portland Cement and partially vitrified
slag and brick. |
| |
|
| Coal Tar |
A dark brown to black cementitious material produced by
the destructive distillation of bituminous coal. |
| |
|
| Coarse Aggregate |
Aggregate retained on the 2.36 mm (No. 8) sieve. |
| |
|
| Coarse-Graded Aggregate |
One having a continuous grading in sizes of particles from
coarse through fine with a predominance of coarse sizes. |
| |
|
| |
|
| Cold In-place Recycling Train |
A unit consisting of a large milling machine towing a screening/crushing
plant and pugmill mixer for the addition of asphalt emulsion and production
of cold mix base. |
| |
|
| Compaction |
The act of compressing a given volume of material into a
smaller volume. |
| |
|
| Consensus Properties |
Aggregate characteristics that must follow certain criteria to satisfy a Superpave
mix design. Specified test values for these properties are not source specific
but widely agreed upon. They include Coarse Aggregate Angularity, Fine Aggregate
Angularity, Flat or Elongated Particles, and Clay Content. |
| |
|
| Consistency |
The degree of fluidity of asphalt cement at any particular
temperature. The consistency of asphalt cement varies with its temperature;
therefore, it is necessary to use a common or standard temperature when
comparing the consistency of one asphalt cement with another. |
| |
|
| Corrugations (Washboarding) and Shoving |
A type of pavement distortion. Corrugation is a form of
plastic deformation typified by ripples across the pavement surface. These
distortions usually occur at points where traffic starts and stops, on
hills where vehicles brake on the downgrade, on sharp curves, or where
vehicles hit a bump and bounce up and down. They occur in asphalt layers
that lack stability. |
| |
|
| Crack and Seat |
A fractured slab technique used in the rehabilitation of
PCC pavements that minimizes slab action in a jointed concrete pavement
(JCP) by fracturing the PCC layer into smaller segments. This reduction
in slab length minimizes reflective
cracking in new HMA overlays. |
| |
|
| Crack |
An approximately vertical random cleavage of the pavement
caused by traffic loading, thermal stresses and/or aging of the binder. |
| |
|
| Crack-Relief Layer |
A large stone, open graded asphalt mixture placed over a
distressed pavement that minimizes reflective cracking by absorbing the
energy produced by movement in the underlying pavement. |
| |
|
| Crusher-Run |
The total unscreened product of a stone crusher. |
| |
|
| Curing |
The development of the mechanical properties of the asphalt
binder. This occurs after the emulsion has broken and the emulsion particles
coalesce and bond to the aggregate. |
| |
|
| Cutback Asphalt |
Asphalt cement that has been liquidized by blending with
petroleum solvents (diluents). Upon exposure to atmospheric conditions
the diluents evaporate, leaving the asphalt cement to perform its function. |
| |
|
| D |
|
| |
|
| Deep Strength Asphalt Pavement |
Pavements containing at least four inches of HMA over non-stabilized
base courses. |
| |
|
| Deflection Basin |
The idealized shape of the deformed pavement surface as
a result of a cyclic or impact load as depicted from the peak measurements
of five or more deflection sensors. |
| |
|
| Deflection |
A load-induced, downward movement of a pavement section. |
| |
|
| Rebound Deflection |
The amount of surface rebound when a load is removed. |
| |
|
| Representative Rebound Deflection |
The mean value of measured rebound deflections in a test
section, plus two standard deviations, adjusted for temperature and most
critical period of the year for pavement performance. |
| |
|
| Residual Deflection |
The difference between original and final elevations of
the pavement surface resulting from the application to, and removal of,
one or more loads from the surface. |
| |
|
| Deflection Sensor |
The term that shall be used to refer to the electronic device(s)
capable of measuring the vertical movement of the pavement; and, mounted
in such a manner as to minimize angular rotation with respect to its measuring
plane at the expected movement. Sensor types include seismometers, velocity
transducers, and accelerometers. |
| |
|
| Delivery Tolerances |
Permissible variations from the exact desired proportions of aggregate and bituminous
material as manufactured by an asphalt plant. |
| |
|
| Dense-Graded Aggregate |
An aggregate that has a particle size distribution such
that when it is compacted, the resulting voids between the aggregate particles,
expressed as a percentage of the total space occupied by the material,
are less than 10%. |
| |
|
| Densification |
The act of increasing the density of a mixture during the
compaction process. |
| |
|
| Design ESAL |
The total number of equivalent 80-kN (18,000-lb.), single-axle
load applications (equivalent single axle loads) expected throughout the
design period. |
| |
|
| Design Lane |
The lane on which the greatest number of equivalent 80-kN
(18,000-lb.) single axle loads (ESAL) is expected. This will normally be
either lane of a two-lane roadway or the outside lane of a multi-lane highway. |
| |
|
| Design Period |
The number of years from the initial application of traffic
until the first planned major resurfacing or overlay. This term should
not be confused with pavement life or analysis period. Adding hot mix asphalt
overlays as required will extend pavement life indefinitely or until geometric
considerations (or other factors) make the pavement obsolete. |
| |
|
| Design Subgrade Resilient Modulus |
The value of the Subgrade Resilient Modulus (MR) used for
designing the pavement structure. It is a percentile value of the subgrade
resilient modulus test data distribution that varies with design ESAL. |
| |
|
| Disintegration |
The breaking up of a pavement into small, loose fragments
caused by traffic or weathering (e.g. raveling). |
| |
|
| Distortion |
Any change of a pavement surface from its original shape. |
| |
|
| Drum Mix Plant |
A manufacturing facility for producing asphalt paving mixtures
that proportions the aggregate, then dries and coats the aggregate with
a proportional amount of asphalt in the same drum. Variations of this type
of plant use several types of drum modifications, separate (and smaller)
mixing drums, and coating units (coater) to accomplish the mixing process.
They are more suited for long runs of the same product. |
| |
|
| Dryer |
An apparatus that will dry the aggregates and heat them
to the specified temperatures. |
| |
|
| Ductility |
The ability of a substance to be drawn out or stretched
thin. While ductility is considered and important characteristic of asphalt
cements in many applications, the presence or absence of ductility is usually
considered more significant than the actual degree of ductility. |
| |
|
| Durability |
The property of an asphalt pavement that represents its
ability to resist disintegration by weathering and traffic. |
| |
|
| E |
|
| |
|
| Edge Joint Cracks |
The separation of the joint between the pavement and the
shoulder, commonly caused by the alternate wetting and drying beneath
the shoulder surface. Other causes are shoulder settlement, mix shrinkage,
and trucks straddling the joint. |
| |
|
| Effective Thickness |
The ratio of the thickness of an existing pavement material
compared to the equivalent thickness of a new HMA layer. |
| |
|
| |
|
| Emulsifying Agent or Emulsifier |
The chemical added to the water and asphalt that keeps
the asphalt in stable suspension in the water. The emulsifier determines
the charge of the emulsion and controls the breaking rate. |
| |
|
| ESAL
(equivalent single axle loads) |
The effect on pavement performance of any combination
of axle loads of varying magnitude equated to the number of 80-kN (18,000-lb.)
single-axle loads that
are required to produce an equivalent effect. |
| |
|
| F |
|
| |
|
| Fatigue Resistance |
The ability of asphalt pavement to resist crack initiation
caused by repeated flexing. |
| |
|
| Fault |
A difference in elevation of two slabs at a joint or crack. |
| |
|
| Fine Aggregate |
Aggregate passing the 2.36 mm (No. 8) sieve. |
| |
|
| Fine-Graded Aggregate |
One having a continuous grading in sizes of particles from
coarse through fine with a predominance of fine sizes. |
| |
|
| Flexibility |
The ability of an asphalt pavement structure to conform
to settlement of the foundation. Generally, flexibility of the asphalt
paving mixture is enhanced by high asphalt content. |
| |
|
| Fog Seal |
A light application of diluted asphalt emulsion. It is used
to renew old asphalt surfaces, seal small cracks and surface voids, and
inhibit raveling. |
| |
|
| Fractured Slab Techniques |
Processes used to rehabilitate PCC pavements by eliminating
slab action through the reduction of slab size (crack/break and seat) or
the pulverization of the PCC slab (rubblization) into essentially a granular
base. |
| |
|
| Full-Depth Asphalt Pavement |
The term FULL-DEPTH (registered by the Asphalt Institute
with the U.S. Patent Office) certifies that the pavement is one in which
asphalt mixtures are employed for all courses above the subgrade or improved
subgrade. A Full-Depth asphalt pavement is placed directly on the prepared
subgrade. |
| |
|
| G |
|
| |
|
| Grade Depressions |
Localized low areas of limited size. |
| |
|
| H |
|
| |
|
| Heavy Trucks |
Two-axle, six-tire trucks or larger. Pickup, panel and light
four-tire trucks are not included. Trucks with heavy-duty, wide-base tires
are included. |
| |
|
| Hot Aggregate Storage Bins |
Bins that store heated and fractionated aggregates prior to their final proportioning
into the mixer. |
| |
|
| Hot Mix Asphalt (HMA) |
High quality, thoroughly controlled hot mixture of asphalt
binder (cement) and well-graded, high quality aggregate, which can be compacted
into a uniform dense mass. |
| |
|
| Hot Mix Asphalt (HMA) Overlay |
One or more courses of HMA over an existing pavement. |
| |
|
| I |
|
| |
|
| Impermeability |
The resistance an asphalt pavement has to the passage of
air and water into or through the pavement. |
| |
|
| K |
|
| |
|
| Kinematic Viscosity |
A measure of the viscosity of asphalt, measured in centistokes,
conducted at
a temperature of 135°C (275°F). |
| |
|
| L |
|
| |
|
| Lane Joint Cracks |
Longitudinal separations along the seam between two paving
lanes. |
| |
|
| Lift |
A layer or course of paving material applied to a base or
a previous layer. |
| |
|
| Lime Treated Subgrade |
A subgrade preparation technique in which the subgrade soil
and added lime are mechanically mixed and compacted to produce a higher
modulus base material than the in-situ material. |
| |
|
| Lime-Fly Ash Base |
A road base material consisting of a blend of mineral aggregate,
lime, fly ash, and water, which when combined in proper proportions and
compacted produces a dense mass of increased strength. |
| |
|
| Load Equivalency Factor (LEF) |
The number of 80-kN (18,000-lb.) single-axle load applications
(ESAL) contributed by one passage of an axle. |
| |
|
| Longitudinal Crack |
A vertical crack in the pavement that follows a course approximately
parallel
to the centerline. |
| |
|
| M |
|
| |
|
| Maintenance Mix |
A mixture of asphalt emulsion and mineral aggregate for
use in relatively small areas to patch holes, depressions, and distressed
areas in existing pavements. Appropriate hand or mechanical methods are
used in placing and compacting the mix. |
| |
|
| Mechanical Spreaders |
Spreader boxes that are mounted on wheels. The spreaders
are attached to and pushed by dump trucks (HMA boxes are pulled and chip
spreaders are pushed). |
| |
|
| Medium-Curing (MC) Asphalt |
Cutback asphalt composed of asphalt cement and a diluent
of medium volatility. |
| |
|
| Mesh |
The square opening of a sieve. |
| |
|
| Micro-Surfacing |
A mixture of polymer modified asphalt emulsion, crushed
dense graded aggregate, mineral filler, additives and water. It provides
a thin resurfacing of 10 to 20 mm (3/8 to 3/4 inch) to the pavement. |
| |
|
| Milling Machine |
A self-propelled unit having a cutting head equipped with
carbide-tipped tools for the pulverization and removal of layers of asphalt
materials from pavements. |
| |
|
| Mineral Dust |
The portion of the fine aggregate passing the 0.075 mm (No.
200) sieve. |
| |
|
| Mineral Filler |
A finely divided mineral product, at least 70 percent of
which will pass a 0.075 mm (No. 200) sieve. Pulverized limestone is the
most commonly manufactured filler, although other stone dust, hydrated
lime, portland cement, and certain natural deposits of finely divided mineral
matter are also used. |
| |
|
| Modified Asphalt Rubber - Asphalt Concrete (MAR-AC) |
High quality, thoroughly controlled hot mixture of modified
asphalt rubber binder (AR) and well-graded, high quality aggregate, which
can be thoroughly compacted into a uniformly dense mass. |
| |
|
| Modified Asphalt Rubber Binder (MAR) |
Conventional asphalt cement to which recycled ground tire
rubber and compounds have been added, that when reacted with the hot asphalt
cement causes a dispersion of the tire rubber particles and compounds. |
| |
|
| Multiple Surface Treatment |
Two or more surface treatments placed one on the other.
The aggregate maximum size of each successive treatment is usually one-half
the previous one. A multiple surface treatment may be a series of single
treatments that produces a pavement course up to 25mm (1 in.) or more in
thickness. A multiple surface treatment is a denser wearing and waterproofing
course than a single surface treatment. |
| |
|
| N |
|
| |
|
| Natural (Native) Asphalt |
Asphalt occurring in nature, which has been derived from
petroleum through natural processes of evaporation of volatile fractions,
leaving the asphalt fractions. The native asphalt of most importance is
found in the Trinidad and Bermudez Lake deposits. Asphalt from these sources
is often called lake asphalt. |
| |
|
| Nondestructive Testing (NDT) |
In the context of pavement evaluation, NDT is deflection
testing, without destruction to the pavement, to determine a pavement's
response to pavement loading. |
| |
|
| O |
|
| |
|
| Open-Graded Aggregate |
One containing less-fine aggregate in which the void spaces
in the compacted aggregate are relatively large and interconnected, usually
10% more. |
| |
|
| Open-Graded Asphalt Friction Course |
A pavement surface course that consists of a high-void,
asphalt plant mix that permits rapid drainage of rainwater through the
course and out the shoulder. The mixture is characterized by a large percentage
of one-sized coarse aggregate. This course prevents tires from hydroplaning
and provides a skid-resistant
pavement surface with significant noise reduction |
| |
|
| P |
|
| |
|
| Pascal-Seconds |
The SI unit for viscosity. 1 Pascal-second equals 10 poises. |
| |
|
| Pavement Base |
The lower or underlying pavement course atop the subbase
or subgrade and under the top or wearing course. |
| |
|
| Pavement Structure |
The entire pavement system of selected materials from subgrade
to the surface. |
| |
|
| Penetration Grading |
A classification system of asphalt cements based on penetration
in 0.1 mm at 25°C (77°F). There are five standard penetration grades
for paving: 40-50, 60-70, 85-100, 120-150, and 200-300. |
| |
|
| Penetration |
The consistency of a bituminous material expressed as the
distance (in tenths of a millimeter) that a standard needle penetrates
a sample vertically under specified conditions of loading, time and temperature. |
| |
|
| Performance Graded (PG) |
Asphalt binder grade designation used in Superpave. It is
based on the binder's mechanical performance at critical temperatures and
aging conditions. |
| |
|
| Planned Stage Construction |
A construction process where stages of the project are performed
sequentially according to design and a predetermined time schedule. |
| |
|
| Plant Mix (Cold) |
A mixture of emulsified (or cutback) asphalt and unheated
mineral aggregate prepared in a central mixing plant and spread and compacted
with conventional paving equipment while the mixture is at or near ambient
temperature. |
| |
|
| Plant Mix Base |
A foundation course produced in an asphalt mixing plant,
which consists of a mineral aggregate uniformly coated with asphalt cement
or emulsified asphalt. |
| |
|
| Plant Screens |
Screens located between the dryer and hot bins, which separate
heated aggregates into proper hot bin sizes. |
| |
|
| Pneumatic-Tire Roller |
A compactor with a number of tires spaced so their tracks
overlap delivering a kneading type of compaction. |
| |
|
| Poise |
A centimeter-gram-second unit of absolute viscosity equal
to the viscosity of a fluid in which a value of stress one dyne per square
centimeter is required to maintain a difference of velocity of one centimeter
per second between two parallel planes in the fluid that lie in the direction
of flow and are separated by a distance of one centimeter. |
| |
|
| Polished Aggregate |
Aggregate particles in a pavement surface that have been
worn smooth by traffic |
| |
|
| Polymer-Modified Asphalt (PMA) Binder |
Conventional asphalt cement to which one or more polymer
compounds have been added to improve resistance to deformation at high
pavement temperatures and often cracking resistance at low temperatures. |
| |
|
| Potholes |
Bowl-shaped openings in the pavement resulting from localized disintegration. |
| |
|
| Power Sweeper |
A power operated rotary broom used to clean loose material
from the pavement surface. |
| |
|
| Present Serviceability Index (PSI) |
A mathematical combination of values obtained from certain
physical measurements of a large number of pavements, so formulated as
to determine, within prescribed limits, the Present Serviceability Rating
(PSR) for those pavements. |
| |
|
| Present Serviceability Rating (PSR) |
The rating assigned to a specific pavement section. |
| |
|
| Present Serviceability |
The ability of a specific section of pavement to serve its
intended use in its existing condition. |
| |
|
| Pumping |
Slab deflection under passing loads sometimes resulting
in the discharge of water and subgrade soils along joints, cracks and pavement
edges. |
| |
|
| R |
|
| |
|
| Rapid-Curing (RC) Asphalt |
Cutback asphalt composed of asphalt cement and a naphtha
or gasoline-type diluent of high volatility. |
| |
|
| Raveling |
The progressive separation of aggregate particles in a pavement from the surface
downward or from the edges inward. |
| |
|
| Reclaimed Asphalt Pavement (RAP) |
Excavated asphalt pavement that has been pulverized, usually
by milling, and is used like an aggregate in the recycling of asphalt pavements. |
| |
|
| Reclaiming Machine |
A self-propelled unit having a transverse cutting and mixing
head inside of a closed chamber for the pulverization and mixing of existing
pavement materials with asphalt emulsion. Asphalt emulsion (and mixing
water) may be added directly through the machine by a liquid additive system
and spray bar. |
| |
|
| Recycled Asphalt Mix |
A mixture produced after processing existing asphalt pavement
materials. The recycled mix may be produced by hot or cold mixing at a
plant, or by processing the materials cold and in-place. |
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| Reflection Cracks |
Cracks in asphalt overlays (usually over deteriorated PCC
pavements) that reflect the crack pattern in the pavement structure below
it. |
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| Residue |
The asphalt binder that remains from an asphalt emulsion
after the emulsifying agent has broken and cured, or the remains of a cutback
after the volatiles have cured |
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| Resilient Modulus of Elasticity (MR) |
A laboratory measurement of the behavior of pavement materials
to characterize their stiffness and resiliency (see Soils Manual, MS-10).
A confined or unconfined test specimen (core or recompacted) is repeatedly
loaded and unloaded at a prescribed rate. The resilient modulus is a function
of load duration, load frequency, and number of loading cycles. |
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| Resistance Value (R-value) |
A test for evaluating bases, subbases, and subgrades for
pavement thickness design. |
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| Road Oil |
Asphalt cement and oils of low volatility, usually similar
to one of the slow-curing (SC) grades. |
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| Roadway |
All facilities on which motor vehicles are intended to travel
such as secondary roads, interstate highways, streets and parking lots. |
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| Roughometer |
An instrumented, single-wheel trailer, which measures the
roughness of a pavement surface in accumulated millimeters, or inches,
per mile. |
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| Rubblization |
The pulverization of a portland cement concrete pavement
into smaller particles, reducing the existing pavement layer to a sound,
structural base that will be compatible to an asphalt overlay. |
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| S |
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| Sand Asphalt |
A mixture of sand and asphalt cement, cutback asphalt or
emulsified asphalt. It may be prepared with sand or clay or combinations
thereof including gravelly clay, gravelly sand, clayey gravel, and sandy
gravel (the names indicate the relative proportions of the materials in
the mixture). Either mixing-in-place or plant mix construction may be employed.
Sand asphalt is used in construction of both base and surface course and
may or may not contain mineral filler. |
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| Sand |
Fine aggregate (any fraction below a No. 8 sieve) resulting
from natural disintegration and abrasion or processing of rock. |
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| Sandwich Seal |
A surface treatment consisting of the application of a large
aggregate, then a spray applied asphalt emulsion, and covered with a smaller
aggregate. |
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| Sandy Soil |
A material consisting essentially of fine aggregate particles
smaller than 2.36 mm (No. 8) sieve and usually containing material passing
a 75 µm (No. 200) sieve. This material usually exhibits some plasticity
characteristics. |
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| Saw-Cut and Seal |
A method of controlling reflective cracking in HMA overlays
that involves constructing joints in the new overlay exactly over the joints
in the existing pavement. |
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| Scaling |
The peeling away or disintegrating of the surface of portland
cement concrete. |
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| Seal Coat |
A thin surface treatment used to improve the surface texture
and protect an asphalt surface. The main types of seal coats are fog seals,
sand seals, slurry seals, micro-surfacing, cape seals, sandwich seals and
chip seals. |
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| Self-Propelled Spreaders |
Spreaders having their own power units and two hoppers.
The spreader pulls the truck as it dumps its load into the receiving hopper.
Conveyor belts move the aggregate forward to the spreading hopper. |
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| Sheet Asphalt |
A hot mixture of asphalt binder with clean, angular, graded
sand and mineral filler. Its use is ordinarily confined to reservoir liners
and landfill caps; usually laid on an intermediate or leveling course. |
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| Shoving |
A form of plastic movement resulting in localized bulging
of the pavement. |
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| Shrinkage Cracks |
Interconnected cracks forming a series of large blocks,
usually with sharp corners or angles. |
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| Sieve |
An apparatus for laboratory work in which the openings in
the mesh are square for separating sizes of material. |
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| Single Surface Treatment |
A single application of asphalt to a road surface followed
immediately by a single layer of aggregate. The thickness of the treatment
is about the same as the nominal, maximum size aggregate particles. |
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| Skid Hazard |
Any condition that might contribute to the reduction of
friction forces on the pavement surface. |
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| Skid Resistance |
The ability of a paved surface, particularly when wet, to
offer resistance to slipping or skidding. Proper asphalt content and aggregate
with a rough surface texture are the greatest contributors. The aggregate
must not only have a rough surface texture, but also resist polishing. |
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| Slippage Cracks |
Crescent-shaped cracks resulting from traffic-induced horizontal
forces that are open in the direction of the thrust of wheels on the pavement
surface. They result when severe or repeated shear stresses are applied
to the surface and there is a lack of bond between the surface layer and
the course beneath. |
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| Slow-Curing (SC) Asphalt |
Cutback asphalt composed of asphalt cement and oils of low
volatility. |
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| Slurry Seal |
A mixture of emulsified asphalt, well-graded fine aggregate,
mineral filler or other additives, and water. A slurry seal will fill minor
cracks, restore a uniform surface texture, and restore friction values. |
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| Soil/Cement Base |
A hardened material formed by curing a mechanically mixed
and compacted mixture of pulverized soil, portland cement and water used
as a layer in a pavement system to reinforce and protect the subgrade or
subbase. |
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| Solubility |
A measure of the purity of asphalt cement. The ability of
the portion of the asphalt cement that is soluble to be dissolved in a
specified solvent. |
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| Source Properties |
Aggregate characteristics that must follow certain criteria
to satisfy a Superpave mix design. Specified values are established by
local agencies. They include Toughness, Soundness, and Deleterious Materials. |
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| Spalling |
The breaking or chipping of a PCC pavement at joints, cracks,
or edges, usually resulting in fragments with feather edges. |
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| Stability |
The ability of an asphalt paving mixture to resist deformation
from imposed loads. Stability is dependent upon both internal friction
and cohesion. |
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| Standard Deviation |
The root-mean-square of the deviations about the arithmetic
mean of a set of values. |
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| Stationary Plants |
Asphalt plants that are so constructed that moving them
is not considered economically feasible. |
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| Steel-Wheel Static Rollers |
Tandem or three-wheel rollers with cylindrical steel rolls
that apply their weight directly to the pavement. |
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| Steel-Wheel Vibratory Rollers |
A compactor having single or double cylindrical steel rolls
that apply compactive effort with weight and vibration. The amount of compactive
force is adjusted by changing the frequency and amplitude of vibration. |
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| Stoke |
A unit of kinematic viscosity equal to the viscosity of
a fluid in poises divided by the density of the fluid in grams per cubic
centimeter. |
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| Structural Overlay |
A HMA overlay constructed for the purpose of increasing
the structural value and ride quality of the pavement system.
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| Subbase |
The course in the asphalt pavement structure immediately
below the base course. If the subgrade soil has adequate support, it may
serve as the subbase. |
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| Subgrade Resilient Modulus |
The modulus of the subgrade determined by repeated load,
triaxial compression tests on soil samples. It is the ratio of the amplitude
of the accepted axial stress to the amplitude of the resultant recoverable
axial strain, generally designated by the symbol MR. |
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| Subgrade, Improved |
Subgrade that has been improved as a working platform by:
1) the incorporation of granular materials or stabilizers such as asphalt,
lime, or portland cement into the subgrade soil; 2) any course or courses
of select or improved material placed on the subgrade soil below the pavement
structure. |
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| Subgrade |
The soil prepared to support a pavement structure or a pavement
system. It is the foundation of the pavement structure. |
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| Superpave Gyratory Compactor (SGC) |
A device used during Superpave mix design or quality control
activities for compacting samples of hot mix asphalt into specimens used
for volumetric analysis. Continuous densification of the specimen is measured
during the compaction process. |
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| Superpave Mix Design |
An asphalt mixture design system that integrates the selection
of materials (asphalt, aggregate) and volumetric proportioning with the
project's climate and design traffic. |
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| Superpave™ |
Short for "Superior Performing Asphalt Pavement" a
performance-based system for selecting and specifying asphalt binders and
for designing asphalt
mixtures. |
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| T |
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| Transverse Crack |
A crack that follows a course approximately at right angles
to the centerline. |
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| Travel Plants |
Self-propelled pugmill plants that proportion and mix aggregates
and asphalt as they move along the road.
There are three general types
of travel plants:
1. One that moves through a prepared aggregate windrow on the roadbed,
adds and mixes the asphalt as it goes, and rear discharges a mixed
windrow ready for aeration
and spreading.
2. One that receives aggregate into its hopper from haul trucks, adds and
mixes asphalt, and spreads the mix to the rear as it moves along the roadbed.
3. Batch mixing units, such as slurry machines, that haul materials to
the site and then mix and apply the materials.
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| Truck Factor |
The number of ESALs contributed by one passage of a vehicle.
Truck Factors
can apply to vehicles of a single type or class or to a group of vehicles of
different types. |
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| U |
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| Upheaval |
The localized upward displacement of a pavement due to swelling
of the subgrade or some portion of the pavement structure. |
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| V |
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| Viscosity Grading |
A classification system of asphalt cements based on viscosity
ranges at 60°C (140°F). A minimum viscosity at 135°C (275°F)
is also usually specified. The purpose is to prescribe limiting values
of consistency at these two temperatures. 60°C (140°F) approximates
the maximum temperature of an asphalt pavement surface in service in the
U.S. 135°C (275°F) approximates the mixing and laydown temperatures
for hot mix asphalt pavements. |
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| Viscosity |
A measure of a liquid's resistance to flow with respect
to time. |
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| W |
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| Well-Graded Aggregate |
Aggregate graded with relatively uniform proportions, from
the maximum size down to filler. |
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| Wet Mixing Period |
The interval of time between the beginning of application
of asphalt material into a pugmill and the opening of the discharge gate. |
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| Whirl Spreaders |
Spreaders that are attached to or are built onto dump trucks.
Aggregate is fed onto the spreader disc through an adjustable opening.
The speed of the disc controls the width of spread. |
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| Workability |
The ease with which paving mixtures may be placed and compacted. |
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Crushers
