Yahya Ghasemi Print III pdf

particle size, shape, grading and packing properties.
݁
=
ܸ
௏
ܸ
ௌ
(2.3) 
where V
v
is the volume of the external granular voids and V
s
is the total volume of the bulk 
sample. 
Particle shape
is a complex function of aggregates’ formation conditions, the mineralogical 
composition, particle size and method of production in case of crushed material. There is 
much confusion on definition of various shape parameters and there are no commonly 
accepted methods for their measurement (Kwan and Mora, 2002).However, particle shape is 
considered as the most important factor influencing water demand and consequently 
workability of a concrete mix. Particle shape can be defined by the help of some other 
measures such as angularity, flakiness, sphericity and so on.

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Flakiness ratio
is defined as the thickness-breadth ratio which can be estimated using the 
thickness guage.
Elongation
ratio is defined as the breadth-length ratio obtained from image 
analysis or based on ASTM D4791-10. 
Sphericity
is usually defined as the ratio of the surface 
area of a sphere having the same volume as the particle to the actual surface area of the 
particle. 
Convexity
is a measure of overall roundness, a rounded particle should not contain 
too many concave corners and a particle containing many concave corners is not rounded.
Surface texture
is difficult to define and is usually being described in quality terms like rough 
or smooth. The surface texture depends on pore structure, texture of the parent rock, 
production method, amount of wear on the particles, and grain size. Surface texture influences 
the surface area and the inter-particle friction of aggregates.
Grading
refers to the size distribution of the aggregates, well-shaped well graded aggregates 
produce more workable concrete. Grading, particularly grading of the fines, is an essential 
factor in production of concrete as it influences the properties of concrete in fresh state. 
Grading also affects void content, water demand and available specific surface area of