Glossary of Asphalt Terms
Used In The ASPHALT
EXPERT SYSTEM ®©:
In the universe of
Modern Asphalt, there is vocabulary that you might want or better should adopt
so that you can
understand your mentors and later that others can understand you.
KEY ABBREVIATIONS:
VC (in % V/V) - Volumetric Concentration
MC (in % M/M) - Mass Concentration
R (in t/m^3) - Density – Mass / Volume
Ratio [M/V] in function of Temperature [T]
VC ss (por) opt / as - Optimum
Volumetric Concentration of Stone Skeleton With Accessible
Pores in Asphalt Specimen / Layer (energy of 4 kJ in lab condition or equivalent
in field condition). Such concentration provides the optimum spatial ‘packing’
without re-granulation if followed guidelines of Rational Asphalt Technology ®©
Mix Design. The KEY VALUE IN the PROCESS of AM COMPOSITION OPTIMIZATION. Stone Material ‘sm’ consists of Stone Skeleton ‘ss’
an aggregate bland that includes all particles between 75-105 microns (usually 90
microns) and the maximal particle size, and Filler (Mix) ‘ft’ that includes
particles ‘90 microns down’ usually a bland of own and added filler
components.) The volume percentage of aggregate in a
mixture is a function of gradation and maximum aggregate size, shape. It
influences "packing" and load transfer through the mixture, which
affects performance.
VC ss (por) max / as – Maximum Volumetric
Concentration of Stone Skeleton With Accessible Pores within
Asphalt Specimen / Layer at DENIED COMPACTION
VC bm opt / as - Optimum Volumetric Concentration of Bituminous Mortar in Asphalt Specimen
/ Layer slightly bellow theoretical maximum density. This is second key value
in a process of HMA COMPOSITION OPTIMIZATION.
(The Bituminous Mortar consists of Rigden
Mortar ‘rm’ and ‘Free’/Intergranular
Bitumen ‘bf’)
VC rm opt /as - Optimum Volumetric
Concentration of Rigden filler mortar in Asphalt
Specimen / Layer. Third key value in a process of HMA
COMPOSITION OPTIMIZATION. (The Rigden Mortar consists of Total Filler Material ‘ft’ and
Bound / Absorbed Bitumen ‘bb’.)
VC v(des) / as - Designed ‘voids’ in asphalt specimen / layer, due to traffic and
climatic conditions and physical incapacity of ANY AM to have NO VOIDS status
regardless of energy given to the system. ‘Spatial Disturbances’ are coming
from Rigdan Mortar. Additional source of ‘trouble’
that can propagate the error is inefficient asphalt technology - especially in
terms of measurement techniques and testing procedures
TMD - Theoretical Maximum Density of Asphalt
Mixture
R as - Bulk Specific Gravity / Density of Asphalt
Mixture
VTM or VC v / as or AV - Total Voids in Asphalt
Mixture
VMA - Voids in Mineral Aggregate
VC b / as - Total Volumetric Concentration of AC /
Bitumen in asphalt specimen / layer (sum of intergranular,
intragranular and bound bitumen)
VC ss / as - Volumetric
Concentration of Stone Skeleton in asphalt specimen /layer
VC bf(int)
/ as or VC bi / as - of Intergranular Bitumen in asphalt specimen/layer
VC bf(ab)
/ as
- of Absorbed Bitumen in asphalt specimen/layer
VC bb / as - of Bound Bitumen in asphalt specimen/layer
VC ns / as - of Natural Sand in asphalt
specimen/layer
VFA - Voids (in Mineral Aggregate) Filled with
Asphalt Cement (Bitumen)
MC b / am - Mass Concentration of Binder in Asphalt
Mixture
R sm - Density of Stone
Material / Aggregate / Mineral Material
R b - Density of Binder
(Bitumen)
R v - Density of Air (Voids)
R ss - Density of Stone
Skeleton
R ss(por) - Density of Stone Skeleton
with PORES
EVC rm / bm or ef VC rm / bm - Effective Volumetric
Concentration of RM in BM
FT - film thickness in microns
Asphalt Mixture Types:
HMA - Hot Mix Asphalt
DGACM - Dense Graded
Asphalt Concrete Mixture
OGFC - P (‘OG-P’) Open
Graded Friction Course Asphalt Concrete Mixture or POROUS AM
SMA - Stone Matrix
Asphalt
RAC (d/w) or RAM -
Rubberized Asphalt Concrete Mixture (dry/wet)
Asphalt Mixture Modifiers:
ICP - Inorganic Color
Pigment Modifier
CR - Crumb Rubber
Modifier
CF - Cellulose Fibers
Modifier
PmB - Polymerized
Bitumen - Modifier
PG - Pulverized Glass
Modifier
OTHER TERMS OF INTEREST:
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 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
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 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 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.
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.
Blow-Up
The localized
buckling or upward movement of a PCC pavement caused primarily by excessive
expansion.
Break and Seat
A fractured slab
technique used in the rehabilitation of Reinforced Concrete Pavement (RCP) that
minimizes slab action by fracturing the PCC layer into smaller segments. This reduction
in slab length (and debonding from the reinforcement
steel) minimizes reflective cracking in new HMA overlays.
Breaking
The phenomenon
when asphalt and water separate in an asphalt emulsion beginning the curing
process. The rate of breaking is controlled primarily by the emulsifying agent,
and somewhat dependent on environmental conditions.
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.
Coarse Aggregate
Aggregate
retained on the 2.36 mm (No. 8) sieve (ASTM standard).
Coarse-Graded Aggregate
One having a
continuous grading in sizes of particles from coarse
through fine with a predominance of coarse sizes.
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 con-sistency 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
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.
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 liquified by blending with petroleum
solvents (diluents). Upon exposure to atmospheric conditions the diluents
evaporate, leaving the asphalt cement to perform its function.
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.
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.
Fatigue Resistance
The ability of
asphalt pavement to resist crack initiation caused by repeated flexing.
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
he 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.
Full-Depth Asphalt Pavement
The term
FULL-DEPTH (registered by the Asphalt Institute with the
Grade Depressions
Localized low
areas of limited size.
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.
Impermeability
The resistance an
asphalt pavement has to the passage of air and water into or through the
pavement.
Kinematic Viscosity
A measure of the
viscosity of asphalt, measured in centistokes, conducted at a temperature of
135°C (275°F).
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.
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.
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.
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
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.
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.
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.
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
The ability of a
specific section of pavement to serve its intended use in its existing
condition.
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.
Reflection Cracks
Cracks in asphalt
overlays (usually over deteriorated PCC pavements) that reflect the crack
pattern in the pavement structure below it.
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.
Resistance
Value (R-value)
A test for
evaluating bases, subbases, and subgrades
for pavement thickness design.
Roughometer
An instrumented,
single-wheel trailer, which measures the roughness of a pavement surface in
accumulated millimeters, or inches, per mile.
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.
Sand Asphalt
The 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.
Sand
Fine aggregate
(any fraction below a No. 8 sieve) resulting from natural disintegration and
abrasion or processing of rock.
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.
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.
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.
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.
Shoving
A form of plastic
movement resulting in localized bulging of the pavement.
Shrinkage Cracks
Interconnected
cracks forming a series of large blocks, usually with sharp corners or angles.
Sieve
An apparatus for
laboratory work in which the openings in the mesh are square for separating
sizes of material.
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.
Skid Hazard
Any condition
that might contribute to the reduction of friction forces on the pavement
surface.
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.
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.
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.
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.
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.
Stability
The ability of an
asphalt paving mixture to resist deformation from imposed loads. Stability is
dependent upon both internal friction and cohesion.
Standard Deviation
The
root-mean-square of the deviations about the arithmetic mean of a set of
values.
Steel-Wheel Static Rollers
Tandem or
three-wheel rollers with cylindrical steel rolls that apply their weight
directly to the pavement.
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.
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.
Structural Overlay
A HMA overlay constructed for the purpose of increasing the structural
value and ride quality of the pavement system.
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.
Subgrade
The soil prepared
to support a pavement structure or a pavement system. It is the foundation of
the pavement structure.
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.
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.
Superpave™ Short for
"
Transverse Crack
A crack that follows a course approximately at right angles to the centerline.
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.
Upheaval
The localized
upward displacement of a pavement due to swelling of the subgrade
or some portion of the pavement structure.
Viscosity
A measure of a
liquid's resistance to flow with respect to time.
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.
Viscosity
A measure of a
liquid's resistance to flow with respect to time.
Well-Graded Aggregate
Aggregate graded
with relatively uniform proportions, from the maximum size down to filler.
Workability
The ease with
which paving mixtures may be placed and compacted.