Building Materials, Third Edition

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— Q

Material Bulk density (kg/m^3 )

Brick 1600–

Granite 2500–

Sand 1450–

Pine wood 500–

Steel 7850

h 2 s
 (
o) is the ratio,

o =

bulk density

density

=

b

It indicates the degree to which the volume of a material is filled with solid matter. For
almost all building materials
o is less than 1.0 because there are no absolutely dense bodies in
nature.

ƒ™™2‡2(
) also known as the unit weight) is the weight per unit volume of material,

 =
. g
Where
 = specific weight (kN/m^3 )

= density of the material (kg/m)
g = gravity (m/s^2 )
Specific weight can be used in civil engineering to determine the weight of a structure
designed to carry certain loads while remaining intact and remaining within limits regarding
deformation. It is also used in fluid dynamics as a property of the fluid (e.g., the specific weight
of water on Earth is 9.80 kN/m^3 at 4°C).
The terms specific gravity, and less often specific weight, are also used for relative density.

ƒ™™2q—2(Gs) of solid particles of a material is the ratio of weight/mass of a given
volume of solids to the weight/mass of an equal volume of water at 4°C.

Gs =

t

t

s

w

=

s

w

At 4° C w = 1 g/cc or 9.8 kN/m^3

„ 22—˜
2™™2—2@q—A 2 If both the permeable and impermeable voids are
excluded to determine the true volume of solids, the specific gravity is called true or absolute
specific gravity.

Ga =

…

…

s a

w

The absolute specific gravity is not much of practical use.

e—22—2™™2—2@q
A 2 If both the permeable and impermeable voids are
included to determine the true volume of solids, the specific gravity is called apparent specific
gravity. It is the ratio of mass density of fine grained material to the mass density of water.