GLOSSARY

Terms which ire defined in the ICAO Lexicon Volume ii (Doe 9110) are used in accordance with the meanings and usage given therein. A wide variety of terms is in use throughout the world to describe soils, construction materials, and components of airport pavements As fur as possible the Terms Used in this document are those which have the widest international use. However, for the convenience of the reader a short list of preferred terms and secondary terms, which are considered to be their equivalent, and their definition, is given below.

preferred term	Secondary Term	Definition
Aggregate		General term for the mineral fragments or particles which, through the agency of a suitable binder, can be combined into a solid mass, e.g., to form a pavement.
Aircraft Classification Number ACN		A number expressing the relative effect of an aircraft on a pavement for a specified Standard sub grade strength.
asphalt concrete	Bitumen concrete	A graded mixture of aggregate, and tiller with Asphalt or bitumen, placed hot or cold, and rolled.
Base course	Base	The layer or layers of specified or selected material of designed thickness placed on a sub‑base or subgrade to support a surface course.
Bearing strength	Bearing capacity Pavement strength	The measure of the ability Qf a pavement to sustain the applied load.
CBR	California Bearing Ratio	The bearing ratio of soil determined by comparing the penetration load of the soil to that of a standard material (gee ASTM D1893). The method covers evaluation of the relative quality of sub grade soils but is applicable to sub‑base and some base course materials.
Composite pavement		A pavement consisting of both flexible and rigid Layers with or without separating granular layers
Flexible pavement		A pavement structure that maintains Intimate contact with and distributes loads to the sub grade and depends on aggregate Interlock particle friction, and cohesion for stability.
Preferred Term	Secondary Term	Definition
Overlay		An additinatil surface Course placed on existing pavement either with or without intermediate base or sub‑base courses. Usually to strengthen the pavement or restore the profile of the surface.
Pavement Classification Number (PCN)		A number expressing the bearing strength of a pavement for unrestricted operations.
Pavement structure	Pavement	The combination of sub‑base, base course. and surface course placed on a sub grade to support the traffic load and distribute it to the sub grade.
Portland cement Concrete	concrete	A mixture of graded aggregate with Portland cement and water.
Rigid pavement		A pavement structure that distributes loads to the sub grade having ag its surface course a Portland cement concrete slab of relatively high bending resistance.
Sub‑base course	sub‑base	The layer or layers of specified selected material of designed thickness placed on a sub grade to support a base course.
Sub-grade	Formation foundation	The upper part of the soil, natural or constructed, which supports the loads Transmitted by the pavement.
Surface course	Wearing course	The top course of a pavement structure.