15 May 2001
GLOSSARY OF SPECIAL TERMS
The most common terms related to asphalt concrete pavements are not defined here since they may
be found in many references, primarily in ASTM D8. Certain terms whose definitions have not been
universally accepted or that have limited usage are defined for this manual as follows:
a. Coarse aggregate. The aggregate retained on the Number (No.) 4 sieve, as described in
American Society for Testing and Materials (ASTM) E11.
b. Fine aggregate. The aggregate passing the 4.75 millimeter (No. 4) sieve and retained on the
75 Fm (No. 200) sieve, often referred to as sand. Natural sand (fine aggregate) is that material which is
found naturally and not manufactured by crushing.
c. Mineral filler. Mineral aggregate particles passing a 75 Fm (No. 200) sieve or commercially
available materials such as lime or cement.
d. Asphalt base course. One or more courses of asphalt mixture placed on a subbase or subgrade
to serve as a base course. This mixture is sometimes called a black base. An asphalt base course is
covered with an intermediate course and surface course.
e. Intermediate course. That portion of a pavement placed on the base course to serve as a
leveling or transition layer between the base and surface courses. Intermediate courses are sometimes
f. Surface course. The top course of an asphalt concrete pavement. The surface course is referred
to as wearing course by many pavement engineers.
g. Optimum asphalt content. The asphalt content of a paving mixture, determined by the Marshall
or gyratory methods of design, that satisfies the applicable Department of Army and Air Force pavement
mix design criteria.
h. Marshall stability value. The maximum load in Newtons (pounds) that can be applied to a
specimen of asphalt concrete paving mixture when tested in the Marshall apparatus.
i. Flow. The deformation, measured in 25 hundredths of a millimeter (hundredths of an inch), that
occurs in a compacted specimen of a paving mixture at the point where maximum load begins to
decrease when subjected to the Marshall stability test.
j. The components of a compacted bituminous mixture are shown below. A given volume of
compacted bituminous concrete consists of air, bitumen, and aggregate.
k. Void calculations of compacted asphalt mixture.
(1) Percent voids total mix (VTM). The percentage of the compacted asphalt concrete mixture
not occupied by the aggregate or asphalt cement.