Asphalt Glossary
Asphalt Production, Paving, and Pavement Maintenance Terms, Definitions & Acronyms
From asphalt cement and balanced mix design to warm-mix asphalt and yield, this glossary defines the essential terms, equipment, materials and pavement technologies used throughout the asphalt industry.
asphalt cement (AC)
Asphalt cement (AC) is the liquid portion/binder used in asphalt pavement mixes. Liquid asphalt is an asphalt material that has a soft enough consistency that it measures beyond the normal penetration test range (the penetration test limit is 300 max). The Asphalt Pro does not use the word “oil” in print or in our digital properties in reference to liquid AC. During the refining of petroleum, one of the residuals becomes the liquid AC used in mix designs. It is no longer classified as oil, and the term “oil” carries negative connotation that we don’t want to wrongly bring into discussions. (This residual is also termed bitumen in non-U.S. resources.)
baghouse
The baghouse is a boxlike, filtering structure at the hot-mix asphalt (HMA) facility. Ductwork carries hot air and dust from the drum to the baghouse, where actual bags (usually aramid fiber bags) “collect” the dust. Jet pulses or reverse air systems (or other technology) cause the bags to release the dust to an auger (or trough) in the floor of the baghouse (usually). From there, the dust is moved to a metering system (usually) to be re-used in the mix production process OR to be siloed for other uses.
balanced mix design
Balanced mix design (BMD) is a method of designing mixes so that they achieve both the anti-rutting performance of Superpave and anti-cracking performance. Not all state DOTs have adopted BMD as of this report (2026), but research entities like the National Center for Asphalt Technology (NCAT) are working diligently to prove testing results and long-term performance of the concept.
blue smoke
Blue smoke is a vapor sometimes seen above an asphalt plant stack or above the silos/loadout. It is caused by extreme temperatures overheating the asphaltenes in the liquid AC. Hot-mix asphalt facilities have many systems available to capture and clean the droplets that “become” blue smoke, so the incidence of blue smoke is lessening in our industry.
bitumen
Bitumen is the international term for the liquid portion/binder used in asphalt pavement mixes. The Asphalt Pro does not use the word “oil” in print or in our digital properties in reference to liquid AC. During the refining of petroleum, one of the residuals becomes the liquid AC used in mix designs. It is no longer classified as oil, and the term “oil” carries negative connotation that we don’t want to wrongly bring into discussions.
carbonation
Carbonation is the permanent sequestering of carbon dioxide.
chip seal
A chip seal is a surface treatment where the pavement is sprayed with emulsified asphalt (or asphalt) and immediately covered with aggregate and rolled. This process uses a special piece of equipment called a chip spreader which distributes the liquid and chips at metered rates.
cold central plant recycling
The process of cold central plant recycling (CCPR) mixes processed/fractionated reclaimed asphalt pavement (RAP) at an ambient-temperature recycling plant to create a foamed (or asphalt emulsion or lime slurry-stabilized) base material. This material is hauled to a nearby paving site. One of the benefits of using CCPR for a project is the reduction of heating costs and reduction of long haul distances by locating the plant/pugmill near the project site.
cold in-place recycling
Cold in-place recycling (CIR) takes place at the site and surface of a pavement system. A reclaimer/stabilizer cuts the top 3 (or more) inches of the pavement surface, grinds the reclaimed asphalt pavement, mixes it with foamed asphalt (or asphalt emulsion binder), and replaces it in place for compaction. (Usually, an additional surface treatment or overlay goes on top.)
cold patch
A pavement maintenance treatment. Cold patch is a mix of liquid AC and aggregate that is applied at ambient temperatures.
compaction
Compaction is the densification of the pavement layer. We achieve compaction of the lift by rolling in static, vibratory, oscillation or seismic mode. (Only Dynapac has seismic mode available on its rollers. Every manufacturer of compaction equipment offers vibratory mode. Multiple OEMs are offering oscillation technology as of 2026.)
coring
Also referred to as “taking cores.” This is a quality control/quality assurance (QC/QA) practice, done behind the paver, to prove densities of the pavement so the contractor can get paid. It’s considered a destructive testing method and patching the core must be performed.
crack
A crack is a fissure in the pavement surface that may extend to lower layers. Cracks typically form after pavement construction because of thermal effects (freeze/thaw cycles), loads greater than the pavement design, deflection in the layer, repetitive loading at sub-fracture stresses and so on.
crack-and-seat
Crack-and-seat is a pavement maintenance method of breaking a failing concrete surface between joints and locking the newly cracked pavement in place for a surface treatment to take place atop it. When used as a verb, it is spelled without the hyphens: “We used a breaker to crack and seat the concrete.” When used otherwise, it includes the hyphens: “We used the crack-and-seat method to fix the pavement system.” “The DOT specified crack-and-seat to fix it.”
crack sealing
A pavement maintenance method. Crack sealing introduces crack sealant material to a working crack. The material sticks to the crack walls while remaining flexible/elastomeric enough that is can absorb strain without fracturing. This lets the crack open and close and flex with thermal and traffic stresses.
crown and slope
The crown in the road is the highest point (in the center; along the centerline), built into the road to assist with water drainage. The lanes will slope gently toward the gutters/curbs/edges so water drains off.
crushed stone
Crushed stone is the product that results from the artificial crushing/processing of rocks, boulders or large cobblestones. The particles resulting from the crushing operation have all faces fractured.
design thickness
The design thickness of a pavement is the total pavement structure thickness above the subgrade.
diamond grinding
Diamond grinding is a pavement maintenance method. The process can use either a series of diamond-tipped saw blades mounted on a shaft or diamond-tipped milling teeth/tools on a specialized drum on a milling machine/cold planer to shave the top surface of a pavement. The goal is to remove bumps, restore the pavement’s rideability and/or improve the surface friction.
endgate
Heated endgates have become the norm in asphalt paving.
EPDs
In agriculture, these are “expected progeny differences” in cattle (and other) husbandry programs. In industrial (thus asphalt and construction) applications, EPDs are environmental product declarations. Asphalt mixes can have EPDs if the producer has tracked his scope one emissions (these are the emissions from company-owned and company-controlled sources) as well as his scope two emissions (these are indirect emissions from utilities/generated power) and his scope three emissions (these are indirect emissions from his vendors). NAPA has an online program that assists producers in tracking inputs to develop EPDs for mixes in the event the state DOT (or other entity) wishes to see them.
fluff factor
The fluff factor is the additional depth a contractor must pave to achieve the proper compaction a job requires. It is calculated by adding a quarter of an inch to each inch of pavement lift. Example: to get a 1-inch lift of compacted asphalt, you place 1.25 inches (this is standard practice with a smooth screed; this fluff amount changes with the SDX screed from Caterpillar).
fly ash
Fly ash is the fines of a coal combustion product. While this is most often used in concrete production, we do see it for full depth reclamation stabilization and other specialized asphalt mixes.
full depth reclamation
Full depth reclamation (FDR) is a pavement rehabilitation technique that pulverizes and blends the full thickness of the asphalt pavement and a portion of the underlying base. The goal is to provide a uniform, homogeneous material for a stabilized base. This is done in one pass, although the reclaimed material may be strengthened by using mechanical, chemical or asphalt stabilization, which can be added during or ahead of pulverization. When performing FDR, it is important to get compaction of the stabilized layer before it cures completely.
ground tire rubber
Ground tire rubber (GTR) is the rubber obtained from processing tires. As of 2026, it is used in some specialty asphalt mixes.
HiMA vs HiMod
Polymer-modified asphalts (PMAs) can be highly modified. If modified by more than 20%, the liquid asphalt is considered highly modified. Kraton Polymers has a trademarked product abbreviated as HiMA, which can be used when discussing the Kraton technology. When discussing other technologies or highly modified asphalts in general, it is appropriate to abbreviate it as HiMod.
hot oil/heating oil
Hot oil is a heating source that runs through pipes at an asphalt tank farm, etc. It is one of the very few times you are allowed to use the word “oil” in the pages of The Asphalt Pro.
intelligent compaction
Almost all rollers (soil and asphalt) have an IC system on them now. The system is designed to give immediate information to the operator so he can achieve compaction of the mat. The system “should” also store data so the contractor can prove he achieved density and get paid. If the roller operator continues to compact a mat that is cooled, he will damage it; breaking the aggregate in the pavement mix. If he doesn’t achieve density before moving on to another part of the mat, the pavement could fail, low spots could form, water could get into the system, etc. IC shows the operator where he still needs to make a pass with the roller or where the mat has cooled too much for a pass to be effective.
international roughness index
The international roughness index (IRI) is a mathematical measurement of a road’s smoothness.
job mix formula
The job mix formula (JMF) is the document that spells out the specifics of the mix design to be used on the project. It will show the binder type and percentage to use, aggregates and gradations to use, fines, additives, temperature to achieve, whether or not the mix can be stored overnight, and so on. The plant may be expected to produce and test the mix according to the JMF before beginning a project, depending on the specs.
job site
The job site is the project site or work zone where paving or pavement maintenance is taking place.
joint filler
Joint filler is a compressible material used to fill a joint. Its purpose is to prevent water and debris getting in.
leveling course
The leveling course of a pavement system (or project) is an asphalt/aggregate mix placed first. It will eliminate irregularities in the contour of an existing surface before the crew performs a treatment or places the next layer. (see lift)
lifecycle
The lifecycle assessment for a pavement is going to be determined by the agency doing the assessing. Spell out lifecycle assessment, no capitalization, lifecycle as one word in this phrase, on first reference. Abbreviate LCA on subsequent references. (If referencing a lifecycle cost assessment, it’s abbreviated LCCA, and it’s more complex.)
lift
This is a noun used to describe a single pull of asphalt (a single placement of an asphalt layer down a lane segment). The Asphalt Pro follows Federal Highway Administration (FHWA) style by indicating the thickness of lifts in inches. (When covering international stories, metric units may follow in parentheses. Some states report the thickness in feet, and we will need to adjust the measurement to inches when reporting.) The bottom layer is the base course, and that lift in the United States is usually an average of 4 or 5 inches. The second layer is the intermediate course, and that lift in the United States is usually an average of 3 to 4 inches. The top layer is the surface course, also called the wearing course or friction course, and that lift in the United States is anywhere from 1 to 3 inches. All of these estimates depend on the mix design, NMAS, region, climate and so on. If you see a single lift of 5 or more inches, in the United States or Canada, double-check the fact. (And then share lots of information about the screed used and compaction/density because it’s an anomaly.)
lockout/tagout
The Occupational Safety and Health Administration (OSHA) has lockout/tagout regulations for mechanics and proxy mechanics to use prior to work on equipment. Spell lockout/tagout as one word each, on either side of the virgule, no spaces, no hyphens. Don’t abbreviate this phrase in any fashion. It is a vital step when performing maintenance and The Asphalt Pro also recommends lockout/tagout for components adjacent to the component being maintained/repaired at HMA or quarry facilities.
longitudinal joint
The longitudinal joint is also referred to as the long joint, the centerline joint or the center seam. This is the centerline joint or the joint between two long pulls/lanes of asphalt. There are different ways to construct the long joint to get optimum compaction/density. One of those methods is the notched wedge joint build. (See entry on the notched wedge joint.)
mill
A cold mill is the large, boxy milling machine (also called a cold planer) seen on the roadway in pavement maintenance operations for mill-and-fill projects. A shear mill is the small, colloidal mixing chamber where polymers and asphalts are “blended” together to create polymer-modified asphalt (PMA).
mill-and-fill
A mill-and-fill is a pavement maintenance operation where a milling machine (or cold planer) removes the top inch (or more) of a pavement and a paving crew immediately replaces the void with a lift of hot-mix asphalt (HMA) or recycled asphalt pavement (RAP). Some sources will insist on calling this technique a mill-and-overlay, which we will allow if the state DOT letting the project designated it as such. (See the entry on overlay.)
mixture
This is the asphalt pavement mix to be placed on a roadway.
NAPA
National Asphalt Pavement Association. Located in Greenbelt, Maryland. See the list of state asphalt pavement associations (SAPA) on the national association’s website for proper nomenclature. Not all state associations follow the same protocol for their name or abbreviations. Not all states have a state association.
NMAS
NMAS is the abbreviation for nominal maximum aggregate size. This is the largest size the aggregate in a mix design can be for the lift thickness being paved and compacted. For example, if you have a lift of 0.5 inches, no stone in that mix can be larger than 0.5 inches. If the aggregate in the mix exceeds the design parameters, it could result in failed density in the field.
notched wedge
The notched wedge is a method of building a longitudinal joint to improve density/compaction. Willow Designs LLC makes a notched wedge joint system called the Notch Wedge (no “ed” in the system’s name; capitalized) that includes the endgate attachment and a pull-behind, rubber-tire roller. Don’t confuse the joint build with the safety edge system. (See the safety edge entry.)
open graded friction course
An open graded friction course (OGFC) is a surface lift with a higher void percentage than normal to allow water to travel through the lift. It is typically sloped so the water will drain off to the side of the pavement. This system design reduces hydroplaning and requires careful pavement maintenance practices to avoid plugging the system with winter salting/de-icing techniques.
overlay
One word. This is a pavement maintenance or pavement preservation technique, depending on the owner/agency’s prerogative, that places a lift on top of existing pavement. Sometimes, the existing pavement has had crackfilling or other minor pavement maintenance performed first. The overlay will vary in depth depending on its function. (Also see the entry for thinlay.)
pavement maintenance
We do not use the phrase “road repair,” which is often seen in mainstream pubs. Pavement maintenance is performed to correct a damaged surface or pavement system. (Side Note: Pavement Maintenance is also the name of a department in The Asphalt Pro where we place articles/information pertaining to any and all levels of maintenance, preservation, recycling, correcting of pavement parts.)
pavement preservation
Pavement preservation often consists of a treatment that restores vitality, seals-and-protects, or otherwise preserves a pavement surface or system so that maintenance is forestalled.
performance grade
As a component of the Superpave system, liquid asphalt cements received performance grade designations. Performance grade is spelled out, no hyphen, in all textual references, but performance-graded is a modifier that should be hyphenated. In asphalt binder designations, PG is abbreviated and is not followed by any spaces. This is the style to follow: PG64-22
perpetual pavement
A perpetual pavement is an asphalt pavement design strategy that results in systems that have a service life of 40 or more years and only need periodic rehabilitation of the top/surface course. The underlying/bottom layers provide enduring structural integrity throughout the lifespan.
The Asphalt Pavement Alliance (APA) is a national organization that bestows the Perpetual Pavement Award on state agencies for asphalt pavements that have been in place for more than 35 years with minimal maintenance (less than 4 inches of pavement thickness gain in their lifetimes) over the years. APA has added award categories for those states that design perpetual pavements of the future. The designation is not capitalized unless used as the proper name of the award.
preventive
Not preventative. This is in keeping with Associated Press style.
project boundaries
The boundaries of a project are the physical outline of the work zone or job site. Prior to the start of paving, the foreman (or superintendent) will paint the boundaries of the project with high-visibility spray paint and to define the paving lanes in their proper paving sequence.
raveling
One “l”. Raveling is a pavement distress.
reclaimed asphalt pavement
This recycled product is reclaimed asphalt pavement (RAP). There are a handful of entities in the industry who have tried to lump multiple materials into the category of “recycled asphalt products” and wish to abbreviate that as RAP. We do not do that at The Asphalt Pro. (It is confusing and unwise to lump our industry successes into one category.)
recycled asphalt shingles
This recycled product is recycled asphalt shingles (RAS). The material is ground, not shredded. There are pre- and post-consumer shingles available to the industry. Both have a high level of AC content, but both have vastly different effects on performance properties due to oxidation of the AC in post-consumer shingles, thus it is important to specify which is being referenced in stories.
recycled waste plastics
We reference plastics in asphalt as recycled waste plastics. This does not have an abbreviation at this time. It is a problematic practice for the asphalt industry and still undergoing much study to make it a viable, long-term mix design additive.
rubblization
Rubblization is the pulverizing of the pavement surface in place. There are huge pieces of equipment called “rubblizers” and “pulverizers” that fracture the pavement for this process. It is spelled without an “e.”
safety edge
A safety edge (not capitalized) is an angled shoulder added to rural roadways to prevent traffic accidents caused by drivers “falling” off the pavement and overcorrecting when trying to climb back up onto the roadway. The angled shoulder is created by paving with an attachment on the paver’s endgate. Carlson (now Astec), TransTech Systems and Willow Designs are some of the OEMs who make these safety edge systems. Don’t confuse these with notched wedge joint systems.
saw cut
Two words. This is a pavement maintenance method whereby the contractor uses a pavement saw to cut out a section of distressed pavement surface. (He then fills the area with hot mix or cold patch to complete the pavement repair.)
sequestration
Sequestration is the storage or removal of carbon dioxide within a product.
shoving
This is a pavement distress.
specification
We have in the past abbreviated state specifications as specs. Also: spec. It’s a colloquialism that we will allow in direct quotes from sources.
stone mastic asphalt
Stone mastic asphalt (SMA) is a mix design with a stone-on-stone structure. It’s also referred to as a stone matrix asphalt, and we accept whichever way the source/researcher prefers to state it. This gap-graded mix design is often used for rutting-resistance.
styrene butadiene styrene
Styrene butadiene styrene (SBS) is a polymer additive used to modify the liquid AC.
Superpave
Superpave. Do not make it all caps. This is the mix design paradigm that came out of the AASHTO projects in the ’90s. It’s why we have PG binders.
tank farm
The tank farm is the area at the asphalt plant where the liquid asphalt cement (AC) and calibration tanks will be located. Even though AC does not “flow” at ambient temperatures, the farm will be surrounded by a berm and located far from the drum and burner. An eye wash station and shower will be located nearby. Tankers approach the tank farm to unload liquid AC (also called binder) into the appropriate tank at a high temperature.
technicians
We have in the past abbreviated this as techs. Also: tech. It’s a colloquialism that we will allow in direct quotes from sources.
thermal profiling
Paver mounted thermal profile (PMTP) technology is the use of a thermal camera mounted atop a paver, feeding multiple data points to a thermal profiling system. Caterpillar, Topcon, Trimble, Vogele and others have such cameras and systems available. It is often used in conjunction with intelligent compaction/infrared (IC/IR) discussions.
Thinlay®
NAPA has trademarked this pavement preservation procedure. To perform a Thinlay is to place a lift that is 0.75 inches or less. Otherwise, call it a thin lift. A thin lift is typically performed as a stop-gap measure to arrest pavement cracking and serve as a pavement preservation technique.
warm-mix asphalt
In keeping with NAPA style, we hyphenate warm-mix asphalt (WMA). Please note: WMA is only a true warm mix if it is produced at temperatures 50 to 80 degrees lower than normal temperatures. In other words, a mix can be produced with a WMA additive to achieve the compaction-aid properties of the additive, but still be produced at 300°F. This is not a warm mix. It is a hot-mix asphalt with a WMA additive.
Women of Asphalt
The Women of Asphalt (WofA) organization formed in 2017 to encourage women in the asphalt industry. The first full-time executive director is Brittyn Heisler (as of 2024). Abbreviate it WofA on subsequent references to differentiate it from the World of Asphalt tradeshow or refer to it as “the national organization” if it’s apparent which org you’re talking about. There are many state branches now, and they are referred to as branches.
World of Asphalt
The World of Asphalt (WOA) tradeshow and conference is held annually in years without a CONEXPO-CON/AGG event. It is managed by the Association of Equipment Manufacturers (AEM).
yield
Yield is the tonnage you’ve placed in a given lane, lift or pull. For example, if you placed 25 tons in the first pull of a parking lot job, that’s your yield for that lift. If you were supposed to only place 22 tons in that pull, that means you’ve gone over by 3 tons and something’s going wrong. The Asphalt Pro has a calculator to assist with yield calculations in the field.
Don’t see a term you’re looking for? Email your suggestion to sandy@theasphaltpro.com. We’ll consider it for inclusion in future updates to The AsphaltPro Asphalt Glossary.