Like many industries, the asphalt industry uses jargon. While the terms may be interchangeable for those working in the asphalt industry, it can be confusing to those unfamiliar with the terminology.  To help the guests to our website, we have created an Asphalt Glossary that contains the common words, phrases, and acronyms.


AASHTO- (American Association of State Highway and Transportation Officials)- An organization of highway engineers from the state transportation agencies which develops guides and standards for use by transportation agencies.

AC- Acronym for Asphalt Concrete, but formerly (pre-2000) used for Asphalt Cement

Aggregate- Any hard, inert, mineral material used for mixing in graduated fragments. It includes sand, gravel, crushed stone or slag.

Asphalt A dark brown to black cementitious material, solid, semisolid or liquid in consistency; in which the predominating constituents are bitumens which occur in nature as such or which are obtained as residue in refining petroleum. Asphalt is a constituent in varying proportions of most crude petroleum

Asphalt Base Course- A foundation course consisting of mineral aggregate, bound together with asphaltic material.  The course generally consists of larger aggregate with the maximum size between ¾” (19 mm) and 1.5” (37.5 mm)

Asphalt Binder- Asphalt that is refined to meet specifications for paving, industrial, and special purposes.

Asphalt Binder Course- An intermediate course between a base course and an asphalt surface course. The binder course is usually a coarse-graded aggregate asphalt concrete containing little or no mineral matter passing through the No. 200 sieve.

Asphalt Blocks- Asphalt concrete molded under high pressure. The type of aggregate mixture composition, amount and type of asphalt, and the size and thickness of the blocks may be varied to suit usage requirements.

Asphalt Block Pavements- Pavements in which the surface course is constructed of asphalt blocks. These blocks are laid in regular courses as in the case of brick pavements.

Asphalt Cement- See Asphalt Binder.

Asphalt Concrete- High quality, thoroughly controlled mixture of asphalt cement/binder and well graded, high-quality aggregate, along with optional recycled materials and additives, thoroughly compacted into uniform dense mass.  This term is often abbreviated AC and may be referred to conversationally as ‘asphalt’.

Asphalt Intermediate Course (sometimes called Binder Course)- A course between a base course and asphalt surface course.

Asphalt Joint Filler- An asphaltic product used for filling cracks and joints in the pavement and other structures.  Overlaying rigid type pavements the overlay should be not less than 4 inches thick to minimize reflection of cracks and joints through the overlay. The greater thickness of overlay may be required depending upon conditions of the old pavement and the traffic to be served.

Asphalt Pavements- Pavements consisting of a surface course of mineral aggregate coated and cemented together with asphalt cement on supporting courses such as asphalt base; crushed stone, slag, or gravel; or on Portland cement concrete, brick or block pavement.

Asphalt Soil Stabilization- (soil treatment) Treatment of naturally occurring non-plastic or moderately plastic soils with liquid asphalt at normal temperatures. After mixing, aeration and compaction provide water-resistant base and subbase courses of improved load bearing qualities.

Asphalt Surface Treatments- Applications of asphaltic materials to any type of road or pavement surface, with or without a cover of mineral aggregate which produce an increase in thickness of less than one inch.

ASTM- (American Society for Testing and Materials)-a national organization of users and producers of materials which establish standards.


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 (Asphalt Base Course).

Binder Course- A transitional layer of bituminous paving between the crushed stone base and the surface course.

Borrow- Suitable material from sources outside the roadway prism used primarily for embankments.

Bituminous Concrete- A designed combination of graded crushed stone, filler and bituminous cement mixed in a central plant, laid and compacted while hot.


CBR (California Bearing Ratio)- A measurement of the strength and support value of a crushed stone base or subgrade soil.

Capillary Action- The rise or movement of water in the voids of a soil due to capillary forces.

Cement Treated Base- Cement-treated base consists of specified soil aggregates and Portland cement concrete mixed in a pug mill and deposited on the subgrade to the specified thickness.

Coarse Aggregate- Aggregate particles retained on the No. 8 sieve.

Coarse Graded Aggregate- One having a continuous grading in size of particles from coarse to fine with a predominance of coarse sizes.

Compaction- The densification of a crushed stone base, subgrade solid or bituminous material by means of vibration or rolling.

Contract- The written agreement executed between the contractor and other parties, setting forth the obligations of the parties thereunder, including, but not limited to the performance of the work, the furnishing of labor and materials, and a basis of payment.

Contractor- The individual, partnership, corporation or joint venture contracting for performance of prescribed work.

Crushed Stone- The product resulting from the artificial crushing of rocks, boulders or large cobble­ stones with the particles resulting from the crushing operation having all faces fractured.

Crusher Run- Aggregates that have received little or no screenings after initial crushing operations. Crusher run aggregates are generally more economical than screened aggregates.

Cul-De-Sac- An area at the terminus of a dead­ end street or road constructed for the purpose of allowing a vehicle to turn around.

Culvert- Any structure not classified as a bridge which provides an opening under any roadway.

Cut- The portion of the roadway formed by excavation below the surface of the earth.

Cutback Asphalt- Asphalt Cement which has been liquefied by blending with petroleum solvents. Upon exposure to the atmospheric conditions, the solvents evaporate, leaving the asphalt cement to perform its function.


Deep Lift Asphalt Pavement- A pavement in which the asphalt base course is placed in one or more lifts of 4 or more inches compacted thickness.

Design CBR- Two thirds the average of all CBR tests taken on the subgrade of an asphalt paving project. This manual uses design CBR rather than average CBR values for determining pavement thickness to compensate for the CBR test values that fall below the average.

Design Thickness- The total pavement structure thickness above the subgrade.

Dense Graded Aggregate- A mineral aggregate uniformly graded from the maximum size down to and including sufficient mineral dust to reduce the void space in the compacted aggregate to exceedingly small dimensions approximating the size of voids in the dust itself.

Drainage- Structures and facilities for collecting and carrying away water.


Earthwork- The work consisting of the construction of the roadway excluding the following: Bridges, Pavement Structure and Selected or Capping Material.

Embankment- A structure of soil, soil-aggregate or broken rock between the embankment foundation and the subgrade.

Emulsified Asphalt- An emulsion of asphalt cement and water which 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 from the discontinuous phase. Emulsified asphalts may be of either the anionic, electro-negatively charged asphalt globules or cationic, electro-positively charged asphalt globules types, depending upon the emulsifying agent.

Equipment- All machinery, tools and other apparatus, together with the necessary supplies for upkeep and maintenance, necessary for the proper construction and acceptable completion of the work.

Erosion- Removal, and transportation of soil by the action of water or wind.


Fine Aggregate- Aggregate particles passing the No. 8 sieve.

Fine Graded Aggregate- One having a continuous grading in sizes of particles from coarse to fine with a predominance of fine sizes.

Flexible Pavement- A pavement structure which maintains intimate contact with and distributes loads to the subgrade and depends on aggregate interlock, particle friction, and cohesion for stability. Asphalt or Bituminous Concrete pavements are flexible pavements. Concrete is not.

Fog Seal- A light application of liquid asphalt without mineral aggregate cover. Slow setting asphalt emulsion diluted with water is the preferred type.

Free Water (Ground Water)- Water that is free to move through a soil mass under the influence of gravity.

French DrainA trench loosely backfilled with stones, the largest being placed on the bottom and the size decreasing toward the top.

Full Depth Asphalt Pavement- An asphalt pavement in which asphalt mixtures are employed for all courses above the subgrade or improved subgrade. A full depth asphalt pavement is laid directly on the prepared subgrade.


Gravel- A coarse granular material (usually larger than 1/•” in dia.) resulting from the natural erosion and disintegration of rock. Crushed gravel is the result of artificial crushing with most fragments having at least one face resulting from fracture.

Green Asphalt– see Warm Mix Asphalt


HMA (Hot Mix Asphalt) – Asphalt concrete mixtures produced at temperatures generally between 270 and 350 degrees Fahrenheit.

Hydrostatic Pressure- The pressure in a liquid under static conditions; the product of the unit weight of the liquid and the difference in elevation between the given points and the free water elevation.


Improved Subgrade- Any course or courses of select or improved material between the foundation soil and the subbase is usually referred to as the improved subgrade. The improved subgrade can be made up of two or more courses of different quality materials.


Leveling Course- An asphalt/aggregate mixture of variable thickness used to eliminate irregularities in the contour of an existing surface prior to superimposed treatment or construction.

Liquid Asphalt- An asphalt material having a soft or fluid consistency that is beyond the range of measurement by the normal penetration test, the limit of which is 300 maximum. Liquid asphalts include cutback asphalt and emulsified asphalts.


Materials- Any substances specified for use in the construction of the project and its appurtenances.

Medium Curing Asphalt (MC)- Liquid asphalt composed of asphalt cement and a kerosene type diluent of medium volatility.

Mineral Dust- The portion of the fine aggregate passing the No. 200 sieve.

Mineral Filler- A finely divided mineral product at least 65% of which will pass a No. 200 sieve. Pulverized limestone is the most common manufactured filler, although other stone dust, hydrated lime, Portland cement, and certain natural deposits of finely divided mineral matter are also used.


Natural Asphalt Asphalt occurring in nature which has been derived from petroleum by natural processes of evaporation of volatile fractions leaving the asphalt fractions. The native asphalts of most importance are found in the Trinidad and Bermudez Lake deposits. Asphalt from these sources is called Lake Asphalt.


Open Graded Aggregate- One containing little or no mineral filler or in which the void spaces in the compacted aggregate are relatively large.


Pavement Structure (Combination Or Composite)-  AII  courses of selected material placed on the foundation or subgrade soil, other than any layers or courses constructed in grading operations. When the asphalt pavement is on an old Portland cement concrete base or other rigid-type bases, the pavement structure is referred to as a combination-or composite-type pavement structure.

Percolation- The movement of free water through the soil.

Permeability- A measure of the rate or volume of flow of water through a soil.

Petroleum Asphalt- Asphalt refined from crude petroleum.

Plans- The standard drawings current on the date bids are received, and the official approved plans, profiles, typical cross sections, electronic computer output listings, working drawings and supplemental drawings, or exact reproductions thereof, current on the date bids are received, and all subsequent approved revisions thereto, which show the location, character, dimensions, and details of the work to be done.

Portland Cement Concrete- A composite material which consists essentially of Portland cement and water as a binding medium within which is mixed coarse and fine particles of crushed stone.

Prime Coat- An application of low viscosity liquid asphalt to an absorbent surface. It is used to prepare an untreated base for an asphalt surface. The prime penetrates into the base and plugs the voids, hardens the top, and helps bind it to the overlying asphalt course. It also reduces the necessity of maintaining an untreated base course prior to placing the asphalt pavement.

Proposal- The offer of a bidder, submitted on the approved official form, to perform the work and to furnish the labor and material at prices set forth therein, valid only when properly signed and guaranteed.


Rapid Curing Asphalt (RC)- Liquid asphalt composed of asphalt cement and a naphtha or gasoline-type diluent of high volatility.

Rehabilitation- The renewal of an existing surface by scarifying and remixing with or without additional material and relaying

Resurfacing- (Sometimes called overlays)­ Existing surfaces may be improved by resurfacing (or overlaying) with a plant mix asphalt mat of varying thicknesses. It may be considered in two categories. (1) Overlays to provide smooth, skid and water resistant surfaces or to make improvements in grade and/or cross-section. (2) Overlays to strengthen existing pavements to handle heavier loads or increased traffic.

Rigid Pavement A pavement structure which distributes loads to the subgrade, having as one course a Portland cement concrete slab of relatively high bending resistance.

Road- A general term denoting a public way for purpose of vehicular travel including the entire area within the right-of-way.

Roadbed- The graded portion of a highway within the top and side slopes, prepared as a foundation for the pavement structure and shoulders.

Rock- From which crushed stone, sand, and gravel are made and the rock most suitable for making good aggregates.


Sand Asphalt- A mixture of sand and asphalt cement or liquid asphalt prepared with or without special control of aggregate grading with or without mineral filler. Either mixed-in-place or plant mix construction may be employed. Sand asphalt may be used in the construction of both base and surface courses.

Seal Coat- A thin asphalt surface treatment used to waterproof and improve the texture of an asphalt surface course.  Depending on the purpose, seal coats may or may not be covered with aggregate.  The main types of seal coats are aggregate seals, fog seals, emulsion slurry seals, and sand seals.

Select Material- Suitable material obtained from roadway cuts, borrow areas, or commercial sources and designated or reserved for use as a foundation for the subbase, for subbase material, shoulder surfacing, or other specific purposes.

Sheet Asphalt- A hot mix of asphalt cement with clean angular, graded sand and mineral filler. Its use is ordinarily confined to the surface course, usually laid on an intermediate or leveling course.

Shoulder- The portion of the roadway contiguous with the traveled way for accommodation of stopped vehicles, for emergency use and for lateral support of base and surface courses.

Slow Curing Asphalt (SC)- Liquid asphalt composed of asphalt cement and oils of low volatility.

Slag- The air-cooled, non-metallic by-product of a blast furnace operation consisting essentially of silicates and alumino-silicates of lime and other bases which is developed simultaneously with iron in a blast furnace. Naturally, it is only available in those localities where pig iron is produced. Crushed slag weighs about 80 lbs. per cubic foot.

Slurry Seal- A mixture of slow-setting emulsified asphalt, fine aggregate, and mineral filler, with water added to produce slurry consistency.

Soil Aggregate- Natural or prepared mixtures consisting predominately of hard, durable particles or fragments of stone, slag, gravel or sand and containing some soil-clay or stone dust conforming to the requirements of specifications.

Soil Cement Base- Consists of a mixture of the natural subgrade material and Portland cement in the proper amounts. After thoroughly mixing, the proper amount of water is added and the material compacted to the required thickness.

Soil Support- A term expressing the ability of the roadbed material, or subgrade soil, to support the traffic loads transmitted through a flexible pavement structure.

Special Provision 5- Special directions, provisions or requirements peculiar to the project under consideration and not otherwise thoroughly or satisfactorily detailed or set forth in the specifications. They set forth the final contractual intent as to the matter involved.

Stage Construction- The construction of roads and streets by applying successive layers of asphalt concrete according to design and a predetermined time schedule.

Street- A general term denoting a public way for purpose of vehicular travel, including the entire area within the right-of-way.

Subbase- The course in the asphalt pavement structure immediately below the base course is the subbase. If the subgrade soil is of adequate quality it may serve as the subbase.

Subcontractor- Any individual, partnership or corporation to whom the contractor sublets part of the contract.

Subdrain-  A structure placed beneath the ground surface to collect and carry away underground water.

Subgrade- The ground underneath the pavement, which serves as the foundation for the pavement structure. Therefore, subgrade is the uppermost material placed in embankments or unmoved from cuts in the normal grading of the roadbed. The subgrade soil is sometimes called “foundation soil”.

Subgrade Stabilization- Modification of roadbed soils by admixing with stabilizing or chemical agents that will increase loadbearing capacity, firmness, and resistance to weathering or displacement.

Surface Course- One or more layers of a pavement structure designed to accommodate the traffic load, the top layer of which resists skidding, traffic abrasion, and the disintegrating effects of climate. The top layer is sometimes called “wearing course”.

Subsurface Drainage- Removal of free water from various structural components of the pavement or the surrounding soil.


Tack Coat- An application of diluted emulsified asphalt applied to increase adhesion between courses (layers) of paving materials.

Thin OverlayA single course of sand asphalt or sand asphalt with no more than 25% of “14” stone, manufactured in an asphalt concrete plant In accordance with specified gradations and specified amount of a specified penetration asphalt.


Underdrain- A perforated or porous-walled pipe placed with suitable pervious backfill beneath the ground surface to collect and carry away underground water.


Viscosity–   This is a measure of the resistance to flow. The term is used as “high viscosity” or “low viscosity”. A high viscosity material would mean a heavy or stiff material which will not flow easily. A low viscosity material would be the opposite. Viscosity is measured in absolute units called poises. It was formerly measured in empirical values of time, distance, and temperature. This method was called Saybolt Furol Viscosity.


WMA (Warm Mix Asphalt)- Asphalt concrete produced at temperatures lower than conventional asphalt or at temperatures similar to conventional asphalt but can be compacted at lower mixture temperatures (i.e. less than 250 degrees Fahrenheit).  Conventional asphalt is produced at plant temperatures between 280 and 350 degrees Fahrenheit depending on the asphalt mixture and time of year.  WMA is produced by either a foaming process, addition of a chemical admixture or a wax-based additive.

Wearing Course–   The top course of asphalt pavements, also called the surface course.