Glossary for Joint AASHTO Training Program - HMA Construction
ADJUSTABLE WIDTH STRIKE-OFF – A movable blade on the leading edge of the screed, for varying the
mat width.
AGGREGATE – Any hard, inert, mineral used for mixing in graduated fragments. It includes sand, gravel,
crushed stone, and slag.
AGGREGATE, COARSE – Aggregate retained on the 2.36 mm (No. 8) sieve.
AGGREGATE, COARSE-GRADED – Aggregate having a continuous grading in sizes of particles from
coarse through fine with a predominance of coarse sizes.
AGGREGATE, DENSE-GRADED – Aggregate that is uniformly graded from the maximum size down to
filler with the object of obtaining an asphalt mix with a controlled void content and high stability.
AGGREGATE, FINE – Aggregate that passes the 2.36-mm (No. 8) sieve.
AGGREGATE, FINE-GRADED – Aggregate having a continuous grading in sizes of particles from coarse
through fine with a predominance of fine sizes.
AGGREGATE, OPEN-GRADED – An aggregate that has a particle size distribution such that when it is
compacted, the voids between the aggregate particles, expressed as a percentage of the total space
occupied by the material, remain relatively large.
AMPLITUDE – On a vibratory roller, the total peak to peak vertical movement per complete cycle of
vibrating roller drum in a freely suspended condition.
ANGLE OF ATTACK – The angle at which the screed bottom travels through the asphalt material.
ANIONIC EMULSION – A type of emulsion such that a particular emulsifying agent establishes a
predominance of negative charges on the discontinuous phase.
APRON – A) The area of the hopper in front of the conveyor. B) The area of the truck bed outside of the tail
gate.
ASPHALT – A dark brown to black cementitious material in which the predominating constituents are
bitumens that occur in nature or are obtained in petroleum processing.
ASPHALT CEMENT – A fluxed or unfluxed asphalt specially prepared as to quality and consistency for
direct use in the manufacture of asphalt pavements, and having a penetration at 25C of between 5 and
300, under a load of 100 g applied for 5 s.
ASPHALT CONCRETE – High quality, thoroughly controlled hot mixture of asphalt cement and wellgraded, high quality aggregate, thoroughly compacted into a uniform dense mass, typified by ASTM
Specification D3515.
ASPHALT INTERMEDIATE COURSE (sometimes called BINDER COURSE) – An asphalt pavement
layer between a base course and an asphalt surface course.
ASPHALT LEVELING COURSE – A course (asphalt aggregate mixture) of variable thickness used to
eliminate irregularities in the contour of an existing surface prior to superimposed treatment or construction.
ASPHALT OVERLAY – One or more courses of asphalt construction on an existing pavement; the overlay
may include a leveling course to correct the contour of the old pavement, followed by uniform course or
courses to provide thickness.
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Glossary for Joint AASHTO Training Program - HMA Construction
AUGER CHAMBER – The area in which the augers are mounted in the asphalt paver.
AUGER – The spiral components mounted to the rear of the conveyor discharge, that spread the asphalt
material evenly across the width of the screed.
AUTOMATIC GRADE and SLOPE CONTROLS – The electronic grade and or slope sensor system that
controls the angle of attack on the screed.
AUTOMATIC MATERIAL FEED CONTROL – A system for automatically controlling the flow of paving
material from the paver hopper to the screed.
AVERAGING – When referring to the screed’s function during a paving operation, the ability of the screed
to correct for a deviation over a long travel distance.
BALANCE – Refers to the equilibrium of forces and factors that affect the screed’s position.
BALLAST – Weight (mass) that is not a permanent part of the compactor.
BANK GRAVEL – Gravel found in natural deposits, usually more or less intermixed with fine material, such
as sand or clay, or combinations thereof; gravelly clay, gravelly sand, clayey gravel, and sandy gravel
indicate the varying proportions of the materials in the mixture.
BASE COURSE – The layer of material immediately beneath the surface or intermediate course. It may be
composed of crushed stone, crushed slag, crushed or uncrushed gravel and sand, or combinations of these
materials. It also may be bound with asphalt or cement.
BEVEL EDGER – An attachment for putting a sloped surface on the edge off the mat.
COMPACTION – Process of removing the air voids in the asphalt material after placement.
CONVEYOR – The chain and flight bar arrangement on each side of the paver that moves material from the
hopper to the augers.
CONVEYOR DECK LINERS – The Ni-hard plates or heavy steel plates used to absorb the wear that occurs
in the bottom of the conveyor area.
CONVEYOR FLOW GATE – A device for regulating the height of paving material being transferred by the
conveyor.
CRACK FILLER – Asphalt material used to fill and seal cracks in existing pavements.
CROSS BEAM – The steel bar connected between the left and right tow arms for mounting the slope
sensor.
CROWN CONTROL – A device that shapes the screed to form a mat with the desired crown.
CROWN – The ability to change the transverse profile of the mat being placed. Also refers to the transverse
profile or the opposite sloping sides of the existing grade.
CRUSHER-RUN – The total unscreened product of a stone crusher.
CUT-OFF SHOE – The detachable plate that fits under the end gates to reduce the paving width of the
screed.
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Glossary for Joint AASHTO Training Program - HMA Construction
CUTBACK ASPHALT – Asphalt cement which has been liquefied by blending with petroleum solvents (also
called diluents). Upon exposure to atmospheric conditions the diluents evaporate, leaving the asphalt
cement to perform its function of cementing and waterproofing.
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 relatively small.
DENSITY – The degree at which air voids have been removed from the asphalt material during compaction.
DEVIATION – A divergence from the straight line, mean or standard.
ELEVATION – The vertical height measured from a reference point or plane.
EMULSIFIED ASPHALT – An blend of asphalt cement and water that contains a small amount of an
emulsifying agent, a heterogeneous system containing two normally immiscible phases (asphalt and water)
in which the water forms the continuous phase of the emulsion, and minute globules of asphalt form the
discontinuous phase. Emulsified asphalts may consist of either anionic, electro-negatively charged asphalt
globules, or cationic, electro-positively charged asphalt globule types, depending upon the emulsifying
agent.
EQUILIBRIUM – Refers to the balance of forces and factors that affect the position or elevation of the
screed.
FEEDERS – The left or right auger-conveyor combination that moves material from the hopper and across
the width of the screed.
FLOW GATES – The vertical adjustable plates located at the rear of the hopper that control the amount or
volume of material that passes from the hopper to the auger chamber.
FRACTURED FACE – An angular, rough, or broken surface of an aggregate particle created by crushing,
by other artificial means, or by nature.
FRAME RAISE – A) The ability of a rubber tired paver to raise or lower the position of the frame and
augers. B) The ability of each of the rear drive tires to move up or down independent of the other tire.
FREQUENCY – On a vibratory roller, the number of complete cycles of the vibrating mechanism per minute.
GRADE – A) Refers to the surface over which paving is to be done. B) Refers to the longitudinal angle of
rise or fall of the roadway. C) Refers to the elevation of the roadway.
GRADE CONTROL – The electronic system for controlling the longitudinal elevation of the mat from a given
reference.
GRADE SENSOR – The electronic sensor unit used for controlling the longitudinal elevation of the mat.
HEAD OF MATERIAL – The given volume and level of material in front of and across the width of the
screed.
HMA BATCH FACILITY – A manufacturing facility for producing asphalt paving mixtures that proportions
the aggregate constituents into the mix by weighed batches and adds asphalt material by either weight or
volume.
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Glossary for Joint AASHTO Training Program - HMA Construction
HMA CONTINUOUS MIX FACILITY – A manufacturing facility for producing asphalt paving mixtures that
proportions the aggregate and asphalt constituents into the mix by a continuous volumetric proportioning
system without definite batch intervals.
HMA DRUM MIX FACILITY – A manufacturing facility for producing asphalt paving mixtures that
continuously proportions aggregates, heats and dries them in a rotating drum, and simultaneously mixes
them with a controlled amount of asphalt material. The same plant may produce cold-mixed asphalt paving
mixtures without heating and drying the aggregates.
HOPPER – The section of the paver that receives the paving material from an external source.
HOT MIX ASPHALT (HMA) – A scientifically proportioned mixture of graded aggregate and asphalt cement
produced at a batch or drum-mixing facility, which is spread and compacted while at an elevated
temperature. To dry the aggregate and obtain sufficient fluidity of the asphalt cement, both must be heated
prior to mixing–giving origin to the term "Hot Mix." Hot Mix Asphalts differ primarily in the type of grading
and amount of asphalt cement used. Asphalt Concrete, Open-Graded Friction Courses, Gap-Graded
Mixes, and Stone Matrix Asphalt (SMA) are examples of Hot Mix Asphalt.
HYDRAULIC STRIKE-OFF – The extendable blade or screeding blade mounted to the front of a standard
screed.
IGNEOUS ROCK – Rock formed by the solidification of magma.
JOINT MATCHER – The grade sensor and skate assembly combination used to match the elevation of an
existing mat or curb.
LIFT – the material placed by an asphalt paving machine in a single pass. An HMA pavement may be
constructed of one of more layers, each consisting of one or more lifts.
LONGITUDINAL JOINT – The area where two mats meet between two paving lanes
MAT – Asphalt materials placed by the paver.
MATERIAL FEED SENSOR – A device used to detect a quantity of paving material in front of the screed.
MATERIAL FEED SYSTEM – The combined conveyor and auger components that transfer paving material
from the hopper and distribute it in front of the screed.
MATERIAL RETAINING PLATE – An attachment installed in front of an auger extension to confine the
paving material in the auger.
MESH – The square opening of a sieve.
METAMORPHIC ROCK – Any rock (e.g. schist, gneiss, etc.) that was formed in some fashion from a preexisting rock, through heat, pressure, the effect of super heated fluids, or any combination of these forces.
MINERAL DUST – The portion of the fine aggregate passing the 75 µm (No. 200) sieve.
MINERAL FILLER – A finely divided mineral product at least 70 percent of which will pass a 75 µm (No.
200) sieve. Pulverized limestone is the most commonly manufactured filler, although other stone dust,
hydrated lime, portland cement, fly ash, and certain natural deposits of finely divided mineral matter are also
used.
MOBILE GRADE REFERENCE – A towed attachment that provides an independent reference for the
automatic grade control.
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Glossary for Joint AASHTO Training Program - HMA Construction
MOLD BOARD – The upper portion of the front of the screed frame that pushes the surplus paving material
distributed by the auger.
NULL OR NULLED – A) Refers to the screed when the face of the screed bottom is resting flat on a surface
with no angle of attack. B) Refers to the automatic screed controls when they are in a position where no
electrical signal is being sent or when the indicator lights are out.
OPERATING WEIGHT – The gross vehicle weight of a roller with full mechanical operating systems plus
one-half tank of fuel, one-half tank of water (if equipped), plus 75 kilograms for the operator. Operating
weight should be designated as either ballasted or unballasted. Ballasted operating weight should include
the location, type(s), amount, and weight of ballast used.
OPERATOR STATION – The designated location(s) from which the operator controls the paver's speed
and direction.
OPERATOR – The person whose primary function is to control the paver's speed and direction.
PAVEMENT STRUCTURE – All courses of selected material placed on the foundation or subgrade soil,
other than any layers or courses constructed in grading operations.
PAVEMENT STRUCTURE COMBINATION- or COMPOSITE-TYPE – When the asphalt pavement is on
old portland cement concrete pavement, a portland cement concrete base, or other rigid-type base or on a
granular base, the pavement structure is referred to as a combination- or composite-type pavement
structure.
PAVER – A self-propelled construction machine (either rubber-tired or crawler-mounted) specifically
designed to receive, convey, distribute, profile and compact paving material by the free-floating screed
method.
PNEUMATIC TIRE ROLLER – A roller that has as its ground engaging means smooth rubber tires. Also
referred to as a rubber tired roller.
PRE-LEVELING – Correction of existing grade or slope deviations before paving is done.
PRE-STRIKE-OFF – The vertical blades mounted to the face or mold board of the screed, used as a
material metering device.
PRIME COAT – An application of low-viscosity asphalt material to an absorptive surface, designed to
penetrate, bond, and stabilize this existing surface and to promote adhesion between it and the construction
course that follows.
PROFILE – A) Refers to the quick changes that occur in the elevation or slope of a mat with the automation
sensors mounted in given positions. B) The shape or slope of a roadway.
PUSH ROLLERS – The device that contacts the tires of the paving material delivery truck.
QUALITY CONTROL/QUALITY ASSURANCE (QC/QA) – the total system of activities that is concerned
with making sure the quality of a product is what it should be.
RECLAIMED ASPHALT PAVEMENT (RAP) – Asphalt pavement or paving material removed from its
original location for use in recycled asphalt paving mixture.
RECYCLED ASPHALT PAVING MIXTURE – A mixture of reclaimed asphalt pavement with the inclusion, if
required, of asphalt cement, emulsified asphalt, cutback asphalt, recycling agent, mineral aggregate, and
mineral filler.
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Glossary for Joint AASHTO Training Program - HMA Construction
RIDEABILITY – A measure of a user’s (e.g. driver’s) satisfaction with the road. It is largely a function of
smoothness.
RIPPLES – The frequent or close changes in elevation of the new mat.
SCREED ARM – The attachment by which the screed is connected and towed by the tractor.
SCREED ASSIST – A hydraulic control system that permits adjusting the weight of a hydraulic extendable
screed to match material design and paving width.
SCREED END PLATE – A vertically adjustable plate at the outboard end of the screed, to retain the paving
material and form the edge of the mat.
SCREED EXTENSION – A fixed or adjustable attachment to the screed for paving at widths greater than
the main screed.
SCREED, FIXED WIDTH – A screed with a constant width that can only be changed by adding or removing
extensions.
SCREED HEATER – A device to heat the screed plate to prevent adhesion of paving material.
SCREED LIFT – A device used to raise the screed.
SCREED PLATE – That component of the screed that shapes and smooths the top surface of the mat.
SCREED – The unit that is towed behind the tractor that shapes, smooths, and controls the depth of the
material being placed.
SCREED TRAVEL LOCK – A device that secures the screed in the raised position.
SCREED, VARIABLE WIDTH – A screed with permanently mounted extensions that can be extended or
retracted to change the mat width while the paver is in operation.
SCREENINGS – A residual product resulting from the artificial crushing of rock, boulders, cobble, gravel,
blast-furnace slag or hydraulic cement concrete, all of which passed the smallest screen used with the
crushing operation and most of which passed the 2.36-mm (No. 8) sieve.
SEDIMENTARY ROCK – A layered rock, formed through the accumulation and solidification of sediments,
which may originally be made up of minerals, rock debris, or animal or vegetable matter.
SEGREGATION – When the coarse aggregates separate from the finer materials within the asphalt mixture
during the HMA production or construction operation.
SIEVE – In laboratory work, an apparatus for separating sizes of aggregate material.
SKI – The floating reference towed beside the screed or tractor that provides a uniform reference for the
grade sensor when constructing an HMA mat.
SLOPE BEAM – The component on which the slope control sensor is mounted.
SLOPE CONTROL – The electronic system that controls the transverse angle of the mat being placed in
reference to horizon.
SLOPE – Refers to the transverse angle of the grade or roadway.
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Glossary for Joint AASHTO Training Program - HMA Construction
SLOPE SENSOR – The electronic unit that detects the transverse angle of the beam it is mounted on.
SOIL AGGREGATE – Natural or prepared mixtures consisting predominantly of stone, gravel, or sand
which contain a significant amount of minus 75 µm (No. 200) silt-clay material.
STEEL SLAG – The nonmetallic product consisting essentially of calcium silicates and ferrites combined
with fused oxides of iron, aluminum, manganese, calcium and magnesium, that is developed simultaneously
with steel in basic oxygen, electric, or open hearth furnaces.
STEERING GUIDE – A sighting device to enable the operator to follow a predetermined course.
STRING LINE – A fixed reference system that utilizes pins rods or bars and a string line and is established
along one or both sides of the intended area to be paved.
SUBBASE – The course in the asphalt pavement structure immediately below the base course is called the
subbase course. If the subgrade soil is of adequate quality there may be no subbase.
SUBGRADE – The soil prepared to support a structure or a pavement system. It is the foundation for the
pavement structure. The subgrade soil is sometimes called "basement soil" or "foundation soil."
SUPERPAVE – An acronym for superior performing asphalt pavements. The performance-based asphalt
mixture design system developed as part of the Strategic Highway Research Program (SHRP).
SURFACE COURSE – The top course of an asphalt pavement, sometimes called asphalt wearing course.
TACK COAT – A very light application of asphalt, usually asphalt emulsion diluted with water. It is used to
ensure a bond between the surface being paved and the overlying course.
TAMPER BAR – A reciprocating component(s) on the screed, used to provide additional compaction of the
paving material.
THICKNESS CONTROL SCREW – A device to manually adjust the mat thickness.
TOW POINT – The point from which the screed is attached and towed forward by the tractor.
TOW POINT CYLINDER – The hydraulic cylinders that raise or lower the tow point position.
TRACTOR – That portion of a paver which provides propulsion and may also receive, convey, and
distribute paving material.
TRANSVERSE JOINT – The area where two mats meet across a paving lane, typically between two
separate days of paving.
TRUCK HITCH – A device used to help position a delivery truck in the proper position relative to the paver
while it (the truck) unloads paving material into the hopper.
TUNNEL – The passageway through which paving material moves form the hopper to the auger/screed.
VIBRATING WEIGHT (MASS) – The weight (mass) of the intentionally vibrating parts in the screed or roller.
VIBRATORS – The shaft, eccentric weight and motor combination that when rotated produces a vibrating
action in the screed or roller.
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