An Area of cracking which resembles the skin of an Alligator. These cracks usually begin as a small area but as water penetrates the area become lager. These cracks are usually created by an underlying base problem or an adhesion problem.
Aggregate
Sand, gravel, crushed stone, RAP (Recycled Asphalt Material), or any other hard materials used to construct the base or make-up the asphalt mix.
Aggregate Base
A base typically constructed of limestone or crushed concrete. The thickness of the base may vary depending on the anticipated traffic loads. In South Louisiana the thickness is typically 6” to 10” thick.
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Asphalt
A dark brown/black material that can be solid, semi-solid, or liquid. Once refined the liquid asphalt is heated and mixed with aggregate to create Hot Plant Mix Asphalt (HPMA) which is used on to build roads and parking lots.
Asphalt Base or Binder Course
The bottom/middle layers of asphalt in the pavement structure. This layer is designed for strength and usually contains larger aggregate with little or no fine material.
Asphalt Mix Design
The “Recipe” for creating Hot Plant Mix Asphalt (HPMA). There are many different mix designs based on anticipated uses, traffic loads, traffic counts, climate, available materials, finished appearance, etc….
Asphalt Overlay
A cost-effective approach to extending the life of an existing concrete or asphalt parking lot. Typically a hot plant mix asphalt overlay is 1.5” to 2” thick. Often a leveling course (layer) is installed prior to the placement of the final lift (surface) to correct any existing drainage issues. This will insure a smooth finished surface with a uniformed thickness.
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Asphalt Wearing or Surface Course
The top layer of asphalt in the pavement structure. This layer is designed for skid resistance, reduced traffic abrasion, effect of climate and appearance.
Base
The material located under the proposed asphalt surface. This could be limestone, crushed concrete, soil cement, or full depth asphalt. Typically the base will range between 6” and 10” thick depending on the anticipated traffic loads of the parking lot or street. As hot plant mix asphalt is considered a flexible surface having an adequate base is very important. The primary cause of asphalt surface failures is the lack of an adequate base.
Base Failure
A term used to describe the condition when the existing base can no longer support the asphalt surface and its intended loads. Base failures are often caused by drainage issues, design flaws, or unanticipated heavy loads. Base failures typically can be corrected by excavating the area and repairing the base with new base material.
Blacktop
A slang term for asphalt pavement.
Crack Filling
A technique in which either a hot-rubberized material or a cold-pour crack filler is poured into existing cracks to minimize water infiltration and help protect the underlying base. Water infiltration is the number one cause of base failures.
Flexible Pavement
A pavement structure that distributes the load to the subgrade with more than one course. Flexible pavements require a base to distribute the load to the subgrade. (Example: Asphalt Paving)
Full Depth Pothole Repair
A type of asphalt pavement repair in which the failed base is excavated to a solid sub-base and then filled with hot plant mix asphalt. The asphalt is placed in multiple lifts with each lift being compacted before placing the next.
Geotextile Fabric
Woven and non-woven fabric like materials that is often placed between the base and sub-base to prevent migration into the sub-grade and help distribute the anticipated traffic loads.
Hot Plant Mix Asphalt
A mixture of sand and aggregate which is uniformly coated with asphalt cement or liquid asphalt and heated in a mixing facility.
Leveling Course
A layer of varying thicknesses of hot plant mix asphalt placed on a parking lot prior to the overlay to eliminate any irregularities and correct drainage issues.
Prime Coat
An application of liquid asphalt to prepare a new base for the asphalt surface. A prime coat is typically placed on a soil cement or aggregate base. Not only does it create a bond between the base and asphalt surface, but also seals the base from water penetration.
Pothole Leveling
Adding hot mix asphalt to a sunken, failed, or damaged area in the existing asphalt surface. The work typically includes cleaning the area of loose dirt and debris, applying a tack coat to the area, filling the area with either hot or cold mix asphalt, and rolling to compact. These repairs are often temporary, as the underlying cause of the failure is not being addressed. Pothole leveling is the quickest and cheapest form of pothole repair.
Reclaimed Asphalt Pavement (RAP)
Milled or ground old asphalt which is added to virgin hot plant mix asphalt. Using RAP is more economical and environmentally friendly. Depending on the project the percent of RAP allowed in the mix may vary.
Reflective Cracking
Cracks in an asphalt overlay which are caused by cracks in the original pavement. Reflective cracks typically appear over joints or stress fractures in the underlying surface. Due to the expansive/contractive characteristics of concrete reflective cracking cannot be prevented when overlaying concrete.
Rigid Pavement
A pavement structure that distributes the load to the subgrade with one course (Example: Concrete Paving)
Seal Coat
A thin asphalt surface treatment that is either spayed on or squeegeed on to an existing asphalt surface. The sealer is designed to reduce oxidation, fill any small cracks, and protect the asphalt surface from vehicle oil drippings.
Slope
The angle of the pavement to allow for proper drainage. Slope is also referred to as the “Fall” or the “Percent Crown”.
Soil Cement Base
An in-place mixture of existing dirt, portland cement, and water to create a base for asphalt pavement.
Soil Stabilization
Modifications to the existing soil by adding chemical agents (Portland cement, lime, ash, etc…) to increase the strength and workability of the soil.
Sub-Base
The Course in the flexible pavement structure located immediately below the base. This course is often the natural subgrade.
Tack Coat
An application of liquid emulsified asphalt to prepare the existing asphalt or concrete surface for an overlay. The tack coat creates a bond between the old and new surface.
Traffic Calming
Using physical designs and structures to improve traffic safety. Traffic calming includes engineering, education, and enforcement. Some common tools used to calm traffic are speed bumps, speed humps, islands, striping, and signage.
