Civil Engineering Reference
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(a)
(b)
(c)
(d)
(e)
FIGURE 1.16
Definitions of volume used for determining density: (a) loose,
(b) compacted, (c) total particle volume, (d) volume not accessible to water, and
(e) volume of solids.
wood and aggregates, voids in the materials require definitions for a variety
of densities and specific gravities. As shown in Figure 1.16(a) and (b), the
bulk volume aggregates will occupy depends on the compaction state of the
material. In addition, the density of the material will change depending on
how the volume of individual particles is measured. Several types of parti-
cle volume can be used, such as the total volume enclosed within the
boundaries of the individual particles, volume not accessible to water or as-
phalt, and volume of solids, as seen in Figure 1.16(c), (d), and (e), respec-
tively. These are important factors in the mix designs of portland cement
concrete and asphalt concrete.
1.3.2 Thermal Expansion
Practically all materials expand as temperature increases and contract as
temperature falls. The amount of expansion per unit length due to one unit
of temperature increase is a material constant and is expressed as the coef-
ficient of thermal expansion
dL
dT
L
a
L
=
(1.13)
dV
dT
V
a
V
=
(1.14)
where
a
L
=
linear
coefficient of thermal expansion
coefficient of thermal expansion
in the length of the specimen
in temperature
a
V
=
volumetric
dL
=
change
dT
=
change
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