Asphalt Industry Glossary

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

Aggregate, Coarse – That retained on the 2.36mm (No. 8) sieve approximately 1/8”.

Aggregate, Coarse‑Graded – One having a continuous grading in sizes of particles from coarse through fine with a predominance of coarse sizes.

Aggregate, Dense‑Graded – Aggregate that is 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 – That passing the 2.36mm (No. 8) Sieve approximately 1/8".

Aggregate, Fine‑Graded – One having a continuous grading in sizes of particles from coarse through fine with a predominance of fine sizes.

Aggregate, Macadam – A coarse aggregate of uniform size usually of crushed stone, slag, or gravel.

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

Asphalt – "A dark brown to black cementitious material in which the predominating constituents are bitumen's that occur in nature or are obtained in petroleum processing." (ASTM Designation D8). Asphalt is a constituent in varying proportions of most crude petroleum's.

Asphalt, Base Course – A foundation course consisting of mineral aggregate, bound together with asphalt material.

Asphalt, Blown or Oxidized – Asphalt that is treated by blowing air through it at elevated temperature to give it characteristics desired for certain special uses such as roofing, pipe coating, under-sealing Portland cement concrete pavement, membrane envelopes, and hydraulic applications.

Asphalt, Concrete – Hot mixture of asphalt cement and graded aggregate, thoroughly compacted into a uniform dense mass typified by ASTM Specification D3515.

Asphalt, Cutback – See Cutback, Asphalt.

Asphalt, Emulsified – See Emulsified Asphalt.

Asphalt, Natural (Native) – Asphalt occurring in nature that 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 Bennudez Lake deposits. Asphalt from these sources often is called Lake Asphalt.

Asphalt, Semi‑Solid – Asphalt that is intermediate in consistency between emulsified and cutback asphalt products and solid or hard asphalt – that is, normally has a penetration between 10 and 300.

Asphalt, Solid or Hard – Asphalt having a normal penetration of less than 10.

Asphalt Cement – Asphalt that is refined to meet specifications for paving, industrial, and special purposes. (See Specifications for Asphalt Cement, ASTM Designation D946 AASHTO Designations M20 and M226.) Asphalt cements are graded by penetration or viscosity. Its penetration is usually between 40 and 300 and its viscosity is between 150 and 4000 poise.

Asphalt Emulsion Slurry Seal (Metro‑Mat) – A mixture of emulsified asphalt, fine aggregate and mineral filler, with water added to produce slurry consistency. Used as a surface and waterproofing course.

Asphalt Fog Seal (Black Seal) – A light application of a diluted asphalt emulsion and without mineral aggregate cover.

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

Asphalt Joint Filler – An asphalt product used for filling cracks and joints in pavement and other structures.

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 Mastic – A mixture of asphalt and fine mineral material in such proportions that it may be poured hot or cold into place and compacted by troweling to a smooth surface.

Asphalt Overlay – One or more courses of asphalt construction on an existing pavement. The overlay generally includes a leveling course, to correct the contour of the old pavement, followed by uniform course or courses to provide needed thickness.

Asphalt Pavement Structure – A pavement structure with all its courses of asphalt‑aggregate mixtures or a combination of asphalt courses and untreated aggregate courses placed above the sub-grade or improved sub-grade.

Asphalt Pavements – Pavement consisting of a surface course of mineral aggregate coated and cemented together with asphalt on supporting courses such as asphalt bases; crushed stone, slag, or gravel.

Asphalt Petroleum – Asphalt refined from crude petroleum.

Asphalt Prime Coat – An application of a low viscosity asphalt product 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.

Asphalt Primer – A low viscosity asphalt product that penetrates into a non‑bituminous surface upon application.

Asphalt Seal Coat – A thin asphalt surface treatment used to waterproof and improve the texture of an asphalt-wearing surface. Depending on the purpose, seal coats may or may not be covered with aggregate. Seal coats are also called surface treatments.

Asphalt Soil Stabilization (Soil Treatment) – Treatment of naturally occurring non‑plastic or moderately plastic soil with emulsified asphalt at ambient temperatures. Aeration and compaction of the asphalt‑soil mixture produce water‑resistant base and sub-base courses of improved load‑bearing qualities.

Asphalt Surface Course – The top course of an asphalt pavement, sometimes called Asphalt Wearing course.

Asphalt Tack Coat – A very light application of a diluted asphalt emulsion. It is used to ensure a bond between the surface being paved and the overlying course.

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 or sand, or combinations of these materials. It also may be bound with asphalt (see Asphalt Base Course).

Bitumen – A mixture of hydrocarbons of natural or pyrogenous origin, or a combination of both; frequently accompanied by non‑metallic derivatives which may be gaseous, liquid, semi‑solid, or solid; and which are completely soluble in carbon disulfide.

Bituminous Pavement Recycling – The re-use, usually after some processing of a bituminous pavement that has already served its first intended purpose.

Cold‑Laid Plant Mixture – Plant mixes that may be spread and compacted at atmospheric temperature.

Cutback Asphalt – Asphalt cement which has been liquefied by blending with petroleum solvents (also called diluents), as for the RC and MC cutbacks (see a. and b. below). Upon exposure to atmospheric conditions, the diluents evaporate, leaving the asphalt cement to perform its function.

  • Rapid‑Curing (RC) Asphalt – Cutback asphalt composed of asphalt cement and a naphtha or gasoline‑type diluent of high volatility. (See specifications for Rapid‑Curing Asphalt, ASTM Designation D2028 or AASHTO Designation M81.)

  • Medium‑Curing (MC) Asphalt – Cutback asphalt composed of asphalt cement and a kerosene‑type diluent of medium volatility. (See specifications for Medium‑Curing Asphalt, ASTM Designation D2027 or AASHTO Designation M82.)

Dense‑Graded Mixture – A mixture of asphalt emulsion and dense graded aggregate.

Emulsified Asphalt – An emulsion of asphalt cement and water that contains 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 asphalt may be of either the anionic, electro-negatively charged asphalt globules, or cationic, electro-positively charged asphalt globule types, depending upon the emulsifying agent. Emulsified asphalt are usually classified by rate of set – RS (Rapid Set); MS (Medium Set); and SS (Slow Set).

Emulsified Asphalt High Float – An asphalt emulsion having a quality, imparted by chemical admixtures, that permits greater resistance to flow, decreased temperature susceptibility, and thicker asphalt films on aggregate particles.

Mineral Dust – The portion of the fine aggregate passing the 75m (No. 200) sieve.

Mineral Filler – A finely divided mineral product at least 70 percent of which will pass a 75m (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.

Mixed‑in‑Place (Road‑Mix) – An asphalt course produced by mixing mineral aggregate and emulsified asphalt at the road site by means of travel plants, or special road‑mixing equipment.

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 that of the previous one, and the total thickness is about the same as the nominal maximum size aggregate particles of the first course. Or, a multiple surface treatment may be a series of single treatments that produces a pavement course up to 38mm (1 1/2 in.) or more. A multiple surface treatment is a denser wearing and waterproofing course than a single surface treatment, and it adds some strength.

Open‑Graded Mixture – A mixture of asphalt emulsion and open graded aggregate.

Pavement Structure – All courses of selected material placed on the foundation or sub-grade soil other than any layers or courses constructed in grading operations.

Plant Mix – A mixture, produced in an asphalt mixing plant, that consists of mineral aggregate uniformly coated with asphalt cement or emulsified asphalt.

Seal Coat – A thin surface treatment used to improve the texture of and waterproof an asphalt surface. 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.

Single Surface Treatments – A single application of asphalt to any kind of road surface, followed immediately by a single layer of aggregate of as uniform size as practicable. The thickness of the treatment is about the same as the nominal maximum size aggregate particles. A single surface treatment is used as a wearing and waterproofing course.

Sub-base – The course in the asphalt pavement structure immediately below the base course is called the sub-base course. If the sub-grade soil is of adequate quality, it may serve as the sub-base.

Sub-grade – The soil prepared to support a structure or a pavement system. It is the foundation for the pavement structure. The sub-grade soil is sometimes called "basement soil" or "foundation soil."

Sub-grade, Improved – Sub-grade, improved as a working platform (1) by the incorporation of granular materials or stabilizers such as asphalt, lime, or Portland cement, prepared to support a structure or a pavement system, or (2) any course or courses of select or improved material placed on the sub-grade soil below the pavement structure. Sub-grade improvement does not affect the design thickness of the pavement structure.

Tar – Brown or black bituminous material, liquid or semi‑solid in consistency, in which the predominating constituents are bituminous obtained as condensates in the destructive distillation of coal, petroleum, oil shale, wood, or other organic materials, and which yields substantial quantities of pitch when distilled.

Thick‑Lift Asphalt Construction – A construction practice in which the asphalt course is placed in one or more lifts of 100mm (4 in.) or more compacted thickness.