Paving Terms and Definitions
This glossary was created to help you understand the most common paving and asphalt terms used in the industry. Each term is explained in simple language so you can better follow along with your paving project.
Aggregates
DEFINTION:
Aggregates are stones, gravel, or crushed rock that make up most of the asphalt mixture. They usually account for about 96% of the final product.
Asphalt
DEFINTION:
Asphalt is also called Bituminous Asphalt Concrete or flexible pavement. It is made by mixing hot asphalt cement with aggregates that compact and harden as they cool.
Asphalt Base
DEFINTION:
Asphalt base is a mix where the largest stone is no bigger than three-quarters of an inch. It is laid on top of a stone foundation to provide strength and support.
Asphalt Binder
DEFINTION:
The asphalt binder layer sits between the base and the surface. It uses coarser materials and provides thickness and durability before the final surface layer is applied.
Asphalt Cement
DEFINTION:
Asphalt cement is a petroleum byproduct that acts as the glue in pavement. It makes up about 4–8% of the mixture while the rest is aggregate.
Asphalt Mat
DEFINTION:
An asphalt mat is the new asphalt surface just behind the paving machine. It is compacted to form the finished pavement.
Base
DEFINTION:
The base is the material layer installed before asphalt paving. It provides the strength and load-bearing ability needed for a long-lasting pavement.
Base Failure
DEFINTION:
Base failure happens when the base layer cannot support the pavement above it. It is often caused by heavy loads, groundwater, or poor design.
Blacktop
DEFINTION:
Blacktop is another word for asphalt, but the meaning can vary by region. Because of this, it is not used in technical project specifications.
C.I.P.R. (Cold In Place Recycling)
DEFINTION:
Cold In Place Recycling grinds existing pavement and reuses it as a base material. Additives like foam asphalt or emulsions are often used for stability.
Chip Seal
DEFINTION:
Chip seal is a process where hot asphalt oil is spread on pavement and topped with small crushed rock. It creates a textured surface but is not recommended for parking lots.
Coal-Tar
DEFINTION:
Coal-tar is a byproduct of steel production used for nearly 80 years as a pavement sealer. Its use has declined in recent years as steel production shifted overseas.
Compaction
DEFINTION:
Compaction means compressing material into a smaller volume. Proper compaction of the sub-grade and base is critical to pavement strength.
Concrete
DEFINTION:
Concrete, or Portland Cement Concrete Pavement, is a rigid building material. It is made from cement, gravel, sand, and water that hardens over time.
Course, Asphalt Base
DEFINTION:
This is a foundation layer made of mineral aggregate bound with asphalt. It provides stability for upper pavement layers.
Cracking
DEFINTION:
Cracking occurs when asphalt separates due to heavy loads, aging, or heat. It is one of the most common forms of pavement distress.
Deflection
DEFINTION:
Deflection is the bending or movement of pavement under weight. It shows how well the pavement can handle loads.
Density
DEFINTION:
Density refers to the weight of asphalt in a specific volume. It is achieved through mechanical compaction after placement.
Drag Box Spreaders
DEFINTION:
Drag box spreaders are pulled behind trucks to distribute asphalt. They are less precise than manufactured pavers and can leave uneven finishes.
Drainage
DEFINTION:
Drainage is the system of pipes and slopes that remove surface water. Proper drainage prevents pavement damage from water pooling.
Emulsion
DEFINTION:
An emulsion is a mix of ingredients that normally don’t combine, like asphalt and water. Special mills and agents make this mixture stable for paving use.
Fall
DEFINTION:
Fall means slope. It describes how pavement is angled to allow water to drain.
Fog Seal
DEFINTION:
Fog seal is a thin spray of diluted asphalt emulsion applied to roads. It restores color, seals small cracks, and slows oxidation.
Full-Depth Asphalt Pavement
DEFINTION:
This method uses asphalt for every pavement layer, including the base and surface. It creates strong, durable roads and parking areas.
Geotextiles
DEFINTION:
Geotextiles are fabric-like materials used in paving. They help stabilize bases, prevent water damage, and reduce cracking.
Gilsonite
DEFINTION:
Gilsonite, also known as North American Asphaltum, is a natural hydrocarbon. It is shiny, brittle, and used in some sealers.
Grade
DEFINTION:
Grade refers to slope or leveling before paving. It ensures water drains properly and creates a smooth foundation.
H.M.A.C. (Hot Mix Asphalt Concrete)
DEFINTION:
Hot Mix Asphalt Concrete is the standard material for most asphalt paving. It is available in many grades depending on traffic and use.
Heat Lance
DEFINTION:
A heat lance uses propane and air to clean and dry cracks before sealing. This method extends the life of crack repairs.
I.S.A. (International Symbol of Accessibility)
DEFINTION:
This is the universal handicap symbol. It marks spaces designed for accessibility.
Infra-Red Repair
DEFINTION:
Infra-red repair uses heat to soften pavement for patching. It allows quick fixes but is not suitable for structural issues.
Joints
DEFINTION:
Joints are seams where two asphalt sections meet. They are often visible after paving.
Laydown
DEFINTION:
Laydown is the step where hot asphalt is placed by paving machines. It is the start of forming the new surface.
Limestone
DEFINTION:
Limestone is a sedimentary rock used in paving bases. It is also a common ingredient in asphalt mixtures.
Nuclear Density
DEFINTION:
Nuclear density testing measures the density of pavement with radiation tools. It ensures proper compaction.
Overlay
DEFINTION:
An overlay is a new layer of asphalt placed over old pavement. It restores surface quality without full replacement.
PCCP (Portland Cement Concrete Pavement)
DEFINTION:
PCCP is a rigid material made from cement, gravel, sand, and water. It is commonly referred to as concrete.
RAP (Reclaimed Asphalt Pavement)
DEFINTION:
RAP is ground asphalt reused in new mixes. It is popular for environmental and cost reasons.
Reflective Cracking
DEFINTION:
Reflective cracking happens when old cracks show through a new overlay. Special fabrics and techniques help reduce it.
Routing
DEFINTION:
Routing enlarges cracks with machines before sealing. This improves the bond and extends repair life.
S.H.R.P. (Strategic Highway Research Program)
DEFINTION:
SHRP is a federal research program focused on paving methods and materials. Its studies shape many modern pavement standards.
Screed
DEFINTION:
The screed is part of a paving machine that spreads and compacts asphalt. Its adjustments determine pavement width and surface profile.
Sealcoating
DEFINTION:
Sealcoating is applying a protective layer over asphalt. It helps preserve, protect, and refresh pavement appearance.
Slope
DEFINTION:
Slope is the angle of pavement for water drainage. It prevents pooling and extends pavement life.
Slurry Seal
DEFINTION:
Slurry seal is a mix of emulsion, aggregate, and additives applied to surfaces. It creates a protective layer and improves durability.
Stone Base
DEFINTION:
A stone base is a crushed rock layer beneath asphalt. It supports the pavement system and distributes weight.
Sub-grade
DEFINTION:
The sub-grade is the prepared soil under the pavement system. It acts as the foundation for the entire structure.
Sub-grade Failure
DEFINTION:
Sub-grade failure occurs when soil cannot support loads above it. It often requires excavation and replacement with stronger material.
Superpave
DEFINTION:
Superpave stands for Superior Performing Asphalt Pavement. It is a design system that considers traffic and climate for durable results.
Surface
DEFINTION:
Surface mix is the top layer of asphalt. It uses small stones and is compacted for a smooth finish.
Tack Coat
DEFINTION:
Tack coat is a thin layer of asphalt oil used between old and new layers. It bonds the surfaces together.
Tracking
DEFINTION:
Tracking happens when asphalt materials stick to tires or shoes and are carried elsewhere. It can make surfaces messy and unsafe.
Transverse Crack
DEFINTION:
A transverse crack is a break across pavement at a 90-degree angle. It usually results from temperature changes or stress.
Transverse Joint
DEFINTION:
A transverse joint is where asphalt sections meet at a 90-degree angle. It is a common feature in road paving.
Wedging
DEFINTION:
Wedging is a leveling layer of asphalt applied before the final surface. It smooths imperfections for a more even pavement.