Glossary

Listed below are some common construction terms.  For more information, or an explanation of a word not appearing in this glossary, please feel free to contact us.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

A - B

Aggregates:  usually various sized stones, crushed rock, gravel, etc. that make up approximately 92-96% of the asphalt mixture.  (Asphalt Cement makes up the other 4-8 %). Asphalt:  the common name for "Bituminous Asphalt Concrete".  It is also known as "flexible pavement".  It is a mixture of aggregates and hot asphalt cement that when placed, compacted and subsequently cooled, becomes the familiar asphalt.   Asphalt Base:  asphalt mix where the largest stone used is no larger than 3/4 of an inch ( typically #57 gradation).  Base mixes are usually laid over a stone base at a minimum depth of 2 inches compacted. Asphalt Base (click on image to enlarge) Asphalt Binder:  the asphalt layer between the base layer of rock or other aggregate and the driving surface layer.  The asphalt binder layer is usually made up of coarser materials and is usually thicker than the surface layer. The binder layer can be used as either a first layer or a driving surface, but its use is actually fairly limited. The vast majority of jobs call for a stone base layer, an asphalt base layer, then a surface layer. Asphalt Cement:  a petroleum byproduct used to "glue" the pavement together.  By volume, this material makes up about 4-8% of the pavement mixture.  (Aggregates make up the other 92-96%).   Asphalt Concrete:  see definition of "Asphalt" above. Base Failure:  base failures occur when the layer beneath the binder layer and driving surface can no longer adequately support the weight of the structure or the traffic.  Base failures can occur for a number of reasons, including:  ground water, excessive load counts (too much weight), and inadequate design.  The failure can be corrected by excavating the failed material and replacing it with bridging stone material.

C - D

Compaction:  compressing a given volume of material into a lesser volume.  A compacted subgrade and base is essential.   Concrete:  the common name for "Portland Cement Concrete Pavement".  A hard, compact building material formed when a mixture of cement, sand, gravel, and water dries.   Cracking:  a separation of the asphalt layer due to excessive loads (weights), heat, or age.   Deflection:  deviation of a pavement from profile under weight loads.   Density ( thickness or compactness): technically, density refers to the weight of a material at a specific volume (unit weight). A specific density of asphalt is achieved my mechanically compacting (rolling) the hot material after it has been placed by the paving equipment. To most consumers of asphalt, it means the compaction of the material versus a theoretical value that is usually derived in a laboratory. Drainage:  a system of drains and pipes for carrying away surface water.  An asphalt surface is sloped to maximize the removal of surface water for vehicular safety.

E - F - G

Fall:  slope.  The degree to which a paved surface is angled to aid in the drainage of water.    Grade:  slope.  The degree to which a paved surface is angled to aid in the drainage of water.   The act of leveling or sloping the subgrade or base layer before paving.

H - I - J - K

Joints: an asphalt joint is the area where two different "pulls" of asphalt meet. This area is usually highly visible after the paving operation and is sometimes referred to as a "seam".

L - M - N - O

Limestone: a sedimentary rock often used as a building material, and for the base layer in an asphalt or PCCP paving system, and the major stone component for asphalt materials produced in our region.   Nuclear Density: measuring the density of a previously placed material achieved by using a special instrument designed to measure the penetration of radiation into that material. Overlay: the practice of placing new asphalt over an existing asphalt or concrete surface. Also called resurfacing.

P - Q - R

Portland Cement Concrete Pavement (PCCP):  a hard, compact building material formed when a mixture of cement, sand, gravel, and water dries.  Commonly known as concrete.  RAP (Reclaimed Asphalt Pavement):  asphalt millings or other asphalt pavements that have been excavated for re-use. The RAP is oftern used as a component of new hot-mixed asphalt. Reflective Cracking:  cracks in the asphalt overlay that mirror the cracks in the original asphalt surface below.  The photo at right illustrates a crack in the asphalt overlay "mirroring" (reflecting) the control joint of the old concrete street under the asphalt.     Reflective Cracking click on image to enlarge

S - T - U - V

Slope:  the degree to which a paved surface is angled to aid in the drainage of water.    Stone Base: the layer in the pavement system below the asphalt binder and driving surface.  The base usually consists of crushed stones of varying sizes and gradations.   Subgrade:  the soil prepared to support an asphalt structure or pavement system.  It is the foundation for the base and the pavement structure.   Subgrade Failure:  subgrade failures occur when the prepared soil beneath the asphalt structure can no longer adequately support the weight of the structure or the traffic.  Subgrade failures can occur for a number of reasons, including:  ground water, excessive load counts (too much weight), and inadequate design.  The failure can be corrected by excavating the soft material from the affected area and replacing it with compacted soil or bridging stone material.   Subgrade Failure click on image to enlarge Superpave:  is short for "Superior Performing Asphalt Pavement".  It is an asphalt design philosophy that uniquely designs roads, parking lots and other asphalt structures according to the environment.  Variables such as weather, the amount of traffic, the type of traffic, etc. are taken into account. Surface: asphalt mix where the largest stone used is no larger than 3/8 of an inch ( typically #8 gradation).  Surface mixes are usually laid at a minimum depth of 1" compacted.    Transverse Crack:  a break in the asphalt pavement that is at a ninety degree angle to the direction of the roadway or the direction in which the asphalt was laid.   Transverse Joint:  a joint in the asphalt pavement that is at a ninety degree angle to the direction of the roadway or the direction in which the asphalt was laid.

W - X - Y - Z

Wedging:  is a layer of asphalt applied as leveling prior to the application of the final driving surface of asphalt.  The wedging layer is intended to even out any imperfections in the existing pavement prior to applying the final layer.