Yahya Ghasemi Print III pdf

2.3. Physical properties of aggregates
The section deals with commonly discussed and used physical properties of concrete 
aggregates: 
Porosity
is defined as the internal pore volume as a proportion of the total volume of a solid,
its significance lies on the influence of porosity of aggregates on concrete density. 

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11 
Aggregates in concrete
݌
=
ܸ
௣
ܸ
௧
(2.1) 
where V
p
is the volume of internal pores and V
t
is the total volume of the solid.
Absorption
can be directly related to the porosity as porous materials can absorb water.
Absorption usually expressed as the ratio of changes in mass of an oven dried sample after 
saturation to the mass of the saturated surface dried sample. Absorption of the aggregates can 
affect concrete strength, workability and durability. 
Moisture state
defines the condition of aggregates in terms of available moisture in the 
particles. Oven dry is a state where the aggregates are conditioned to temperature of 100 to 
110
o
C to evaporated the available moist in the particles, air dry is when the aggregate has 
reached equilibrium with the ambient air; saturated surface dry (SSD) is a condition when the 
aggregates themselves are saturated but the surface has been dried. The moisture state is 
important as it influences the total water content of the mix affecting strength and workability. 
Density
of a solid is defined as the ratio of its mass to the volume it occupies.
ߩ
=
ܯ
ௌ
ܸ
ௌ
(2.2) 
where M
s
and V
s
are the mass and the volume of the solid, respectively. 
There are several measures of density among which bulk density and relative density are the 
most important ones. Bulk density is the density of the material in bulk granular form. 
Relative density is the ratio of the density of substance to the density of a given reference 
material (usually water). Logically, The aggregates density affects the proportioning of 
concrete ingredients. 
Void content
applies to a collection of particles as the particles do not fit together perfectly 
thus leaving voids between them. The volume of the voids is of great importance in concrete 
industry as the voids should be filled with paste or matrix. The void content is a function of