4. Permeability is a measure of the ease with which a fluid, most commonly water,
will flow through a material. Gravels have relatively high permeability, whereas
sands and silts have lower permeability.
PERMEABILITY AND FILTERS
k = (D10)2
Where:
k = coefficient of permeability (cm/s)
D10 = effective sized based on gradation curve (mm)
5. The best permeability is obtained by using aggregate as large as possible and as
uniform in size as possible.
Size and gradation are of primary importance for a filter.
Where filter particles are too small, the filter becomes plugged, and where filter
particles are too large, particles that should be caught are allowed to pass through.
PERMEABILITY AND FILTERS
9. Particle sizes are important for all applications. The concept of aggregate size is
difficult to express because the particles have odd shapes that cannot be measured
easily and the shapes and sizes vary greatly in any one sample. The important
features are range of sizes, or smallest and largest particles, and gradation, or
distribution of sizes within the range covered. A few very large particles or a few very
small particles do not ordinarily affect the performance of the mass of aggregate.
Therefore, what is usually important is the range from the smallest particles that are
contained in a significant amount to the largest particles that are contained in a
significant amount.
SIZE AND GRADATION
10. A sieve consists of a circular frame holding wires strung in such a way as to form
square holes of a designated size. Particles are considered to be the size of the
holes in the sieve on which they are caught. Whether or not flat particles and long,
narrow ones go through a screen may depend on how they land on the screen while
being shaken. Thus, chance may play a minor part in the number of particles
retained on or passing through a sieve. Statistically, results are the same over a
large number of tests of the same material. Extremely flat or elongated particles,
which could cause the greatest variations, are unacceptable in nearly all cases and
so are not ordinarily tested by sieve analysis.
SIZE AND GRADATION
17. The surface area of a quantity of aggregate is sometimes
important. A ratio of surface area to volume or surface area to
weight is determined and used for computations dealing with
surface area. Of all possible particle shapes, a sphere has the
lowest ratio of surface area to volume or weight. .
SURFACE AREA
18. The total volume of an aggregate consists of solid particles
and the voids between the particles. The total volume is
important because aggregate must be ordered to fill a certain
volume.
The volume of solid matter is also of importance. The volume
of one aggregate particle consists of a mass of solid material.
WEIGHT-VOLUME RELATIONSHIP
19. 1. The volume of aggregate may include solid matter, plus pores in the particles, plus voids. This is called
bulk volume of aggregate.
2. The volume may include solid matter, plus pores in the particles but not voids. This is called the
saturated, surface-dry volume.
3. The volume may include solid matter only, not pores or voids. This is called solid volume.
4. The weight may include solid matter, plus enough water to fill the pores, plus free water on the particle
surface. This is called wet weight.
5. The weight may include solid matter, plus enough water to fill the pores. This is called saturated,
surface-dry weight.
6. The weight may include solid matter only. This is called oven-dry weight.
WEIGHT-VOLUME RELATIONSHIP
20. WEIGHT-VOLUME RELATIONSHIP
SPECIFIC GRAVITY
Specific gravity (SG) of a substance is the ratio of the solid unit weight of that substance to the unit weight of
water. The specific gravity of aggregate particles is useful in calculations, particularly those to convert weight
of the irregularly shaped particles to saturated, surface-dry volume or to solid volume.
Two Kinds of Specific Gravity:
1. Bulk Specific Gravity
- is based on oven-dry weight and saturated, surface-dry volume of the aggregate particles. Pores in the
particles are considered part of the volume.
2. Apparent Specific Gravity
- is based on oven-dry weight and solid volume of the particles. Either one of these can be considered as a
true specific gravity, and each has its own use.
21. WEIGHT-VOLUME RELATIONSHIP
SPECIFIC GRAVITY
A type of specific gravity called effective specific gravity is used in the design of asphalt
concrete. It is derived by dividing oven-dry weight by the weight of a volume of water equal to
the solid volume plus the volume of pores that is not filled with asphalt cement when aggregate
and cement are mixed.
24. SPECIFIC
GRAVITY Bulk Specific Gravity (also known as Bulk Dry Specific Gravity)
Bulk SSD Specific Gravity
Apparent Specific Gravity
SSD
25. SPECIFIC GRAVITY
A. Bulk Specific Gravity (also known as Bulk Dry Specific Gravity)
Gsb = A/(B-C)
Where:
A = Oven dry weight
B = SSD weight
C = Weight in water
26. SPECIFIC GRAVITY
B. Bulk SSD Specific Gravity (Gsb SSD)
Gsb SSD = B/(B-C)
Where:
B = SSD weight
C = Weight in water
30. Excessive amounts of foreign material are detrimental in aggregate
used for any purpose.
ASTM C33 contains allowable limits for seven types of deleterious
substances which must be controlled in aggregates to be used for
portland cement concrete.
DELETERIOUS MATTER
31. SEVEN TYPES OF DELETERIOUS SUBSTANCE
FRIABLE PARTICLES MATERIAL FINER THAN
NO. 200 SIEVE
SOFT PARTICLES LIGHTWEIGHT
PIECES
CHERT ORGANIC IMPURITIES REACTIVE AGGREGATES
32. Toughness is a property of the aggregate that resist the abrasion
and impact.
Toughness is an important quality for aggregate subjected to
mixing in a portland cement concrete mixer or an asphalt concrete
pugmill.
MISCELLANEOUS PROPERTIES
34. - Aggregates tests and inspection must be performed on representative
samples
SAMPLING
1. Preliminary Investigation of a possible source of supply.
2. Acceptance or Rejection of a source of supply by the buyer.
3. Acceptance or Rejection by the buyer specified material from the supplier.
4. Control of removal and processing operations.
37. - refers to materials used in construction that possess unique properties or
characteristics, distinct from traditional fine and coarse aggregates
SPECIAL AGGREGATES
Kinds of Aggregates:
Lightweight Aggregates - These are aggregates with low bulk density,
making them lighter than traditional aggregates.
Heavyweight Aggregates - Heavyweight aggregates have higher density
than normal aggregates.
Recycled Aggregates - are derived from waste materials such as concrete
rubble, asphalt, and demolition debris.
38. Expansive Aggregates - this expands when they come into contact with
water.
Decorative Aggregates - are especially designed for the purpose of being
utilized in landscaping projects.
Specialty Mineral Aggregates - are used as aggregates for their unique
properties.
Explosive Aggregates - these aggregates, like ammonium nitrate and
ammonium sulfate, are used in explosive materials for construction
purposes, such as in mining and demolition operations.
SPECIAL AGGREGATES