Chapter 1 Aggregates:
1. Identify three applications in infrastructure where aggregate is important.
Answer:
a) As a bound material in concrete and asphalt
b) As an unbound medium used to provide support for various infrastructure components, or
c) For filtration to remove particles from water (runoff or treatment)
2. Describe the geologic origins of aggregate and provide some examples of the rock source.
Answer:
All aggregate (and soils) come from rock, which is a natural material of mineral grains
connected by strong permanent chemical bonds. Rocks are subject to breakdown by physical
(mechanical) and chemical processes when exposed to the elements. The souse rocks
include:
Igneous rock, which is excellent for construction purposes and includes granite, basalt,
etc.
Sedimentary rock, which has relatively good engineering properties and includes
sandstone, limestone, etc.
Metamorphic rock, which can have excellent engineering properties, like igneous rock.
3. Discuss some advantages and disadvantages of aggregate use.
Answer:
Advantages:
Provides structural stability and improved drainage when used as a base for roads
(both flexible and rigid payment) and buildings.
Aggregate is easier to compact; it is insensitive to the presence of water; it is not
susceptible to frost action in cold regions; and it is relatively incompressible.
As part of a composite material in concrete or asphalt, aggregate can greatly lower the
overall cost since aggregate can make up over 80% in concrete and as much as 95%
in asphalt.
When used as a filter to remove particles from water, aggregate can afford many
advantages over synthetic filters, including reduced cost, reduced environmental
impact, etc.
Disadvantages
When used as a base for infrastructure projects, site preparation may add significant
cost and time to complete the project.
In the case of asphalt and concrete, depending on the quality of the aggregate it may
lower the strength.
4. Describe the methods by which aggregates can be classified.
Answer:
Aggregate can be classified by size, source, and weight.
, Size: fine aggregate with particle sizes from 0.0029 inches to 3/16 inches and coarse
aggregate with particle sizes from 3/16 inches to 3.0 inches.
Source: natural aggregate is typically dredged from river and lake bottoms or
excavated from pits or quarries; manufacturedfrom various synthetic materials that
can be considered waste, such as crushed air-cooled blast furnace slag; and recycled,
which is considered synthetic because the parent material is derived from crushing
inert construction, demolition, and other waste materials.
Weight: classified into three categories based on its unit weight (bulk density):
o Normal weight aggregate with bulk unit weight (in pounds per cubic foot, pcf)
from 75 to 110 and specific gravity between 2.4 and 2.8,
o Lightweight aggregate with bulk unit weight from 35-pcf to 70-pcf and
specific gravity less than 2.4,
o Heavyweight aggregate with bulk unit weight greater than 130-pcf and
specific gravity greater than 2.8.
5. Provide three reasons why natural aggregate is different from manufactured aggregate.
Answer:
Natural aggregate is typically dredged from river and lake bottoms or excavated from
pits or quarries.
Natural aggregate can be created by crushing various types of rock (hard rock for
gravel and friable sandstone for sand).
Natural aggregate is not produced by synthetic means.
6. List three waste products that can be used as recycled aggregates.
Answer:
Construction or demolition waste
Crushed concrete derived from construction or demolition waste.
Scrap tires and glass
7. How are aggregates classified as coarse or fine?
Answer:
Fine aggregate with particle sizes from 0.0029 inches to 3/16 inches.
Coarse aggregate with particle sizes from 3/16 inches to 3.0 inches.
8. Explain the difference between density and specific gravity.
Answer:
Density is the mass per unit volume of a material and is expressed in units of g/cm3 or lb/ft3;
whereas specific gravity (also known as relative density) is the ratio of density of a material
to the density of water and is dimensionless.
9. Explain the difference between oven dry specific gravity, saturated surface dry specific
gravity, and the apparent specific gravity.
Answer:
Oven dry specific gravity is the oven dry density divided by the density of water.
Oven dry density is the weight of solid portion of an aggregate divided by the volume
of the aggregate particle, which includes the solid volume plus the volume of
permeable and impermeable pores of the aggregate.
, Saturated surface dry specific gravityis the saturated surface dry density divided by
the density of water. Saturated surface dry density is the weight of solid plus the
weight of water within the permeable pores of the aggregate particledivided by the
bulk volume of an aggregate particle, which includes the solid matter plus the volume
of permeable and impermeable pores.
Apparent specific gravity is the apparent density divided by the density of water.
Apparent density is the weight of the solid portion of an aggregate divided by the
volume of the aggregate particle, which only includes the solid portion and the
impermeable pores (i.e., it does not include permeable pores).
10. Describe three types of grading in aggregate and explain how their gradation charts would
differ. What is the preferred gradation type of an aggregate in Portland cement concrete and
why?
Answer:
Well-Graded. A well-graded aggregate is one where the aggregate sizes are present in
approximately equal proportions. A well-graded gradation chart will appear linear (i.e.,
with a constant slope).
Uniform. A uniform gradation means that a large quantity of the particles is approximately
the same size, which will result in a gradation curve that is nearly vertical near the sieve
numbers where the most weight is retained.
Gap-Graded. A gap-graded aggregate is one where most aggregates are large or small, and
very few particles of an intermediate size are present. A gradation chart is nearly horizontal
at the sieve number for the gap (or skipped) aggregate size.
The preferred gradation type of an aggregate in Portland cement concrete is well-graded
because the distribution of particle sizes will result in a low presence of voids since small
particles will fill those voids.
11. An acquired sample of fine aggregate was weighed with an initial mass of 549-g. The table
below provides a list of sieves used in the analysis and the weight of particles retained on
each sieve.
a) Determine the percent retained and the cumulative percent retained on each sieve.
b) Plot the gradation curve for the fine aggregate test sample. Describe the type of
gradation of the sample.
c) Calculate the fineness modulus of the test sample.
Sieve Analysis Data
Sieve Weight of
Opening Particles
Sieve Size Retained on each
Size (mm) Sieve, w (g)
3/8 in 9.50 0.0
#4 4.76 16.0
#8 2.36 35.4
#16 1.18 75.3
, #30 0.6 169.5
#50 0.3 156.2
#100 0.15 52.5
#200 0.074 28.9
Pan -- 13.2
Answer:
Sieve Analysis Data and Calculation Results.
Sieve Weight of Weight Fraction %
Opening Particles Retained on Cumulative
Sieve Size Retained on Each Sieve, W Retained, %Passin
Size (mm) each Sieve, w(g) (%) CW g, WP
3/8 in 9.50 0.0 0.0% 0.0% 100%
#4 4.76 16.0 2.9% 2.9% 97.1%
#8 2.36 35.4 6.5% 9.4% 90.6%
#16 1.18 75.3 13.8% 23.2% 76.8%
#30 0.6 169.5 31.0% 54.2% 45.9%
#50 0.3 156.2 28.6% 82.8% 17.3%
#100 0.15 52.5 9.6% 92.4% 7.7%
#200 0.074 28.9 5.3% 97.7% 2.4%
Pan -- 13.2 2.4% 100% 0.0%
i) Calculate the weight fraction of aggregates retained on each sieve.
The weight fraction retained on a sieve, Wsieve, is calculated as the weight of particles retained
on the sieve divided by the final total weight of all aggregate particles,
𝑤𝑠𝑖𝑒𝑣𝑒
𝑊𝑠𝑖𝑒𝑣𝑒 =
𝑤𝑓,𝑡𝑜𝑡𝑎𝑙
The calculation is demonstrated for the #4, #8, and #16 sieves, which are on rows 2, 3, and 4
respectively. The resulting percentage of aggregate particles retained on each sieve are
shown in the fourth column.
16
# 4 Sieve: 𝑊#4 = = 0.029 = 2.9%
547
35.4
#8 Sieve: 𝑊#8 = = 0.065 = 6.5%
547
75.3
#16 Sieve: 𝑊#16 = = 0.138 = 13.8%
547
ii) Calculate the cumulative percentage weight retained on each sieve.
The cumulative percentage weight retained, CWsieve, is the fraction of the aggregate weight
that does not pass a specific sieve. It is calculated by summing the weight fraction, Wsieve,
retained on a particular sieve plus the weight fraction retained on each of the sieves above, or
larger than the sieve of interest. The cumulative weight percentage retained on each sieve is
simply a running total of weight fractions. To illustrate the calculation, the cumulative
percent weight retained, CWsieve, on sieves #8, #16, and #30 are calculated as follows:
1. Identify three applications in infrastructure where aggregate is important.
Answer:
a) As a bound material in concrete and asphalt
b) As an unbound medium used to provide support for various infrastructure components, or
c) For filtration to remove particles from water (runoff or treatment)
2. Describe the geologic origins of aggregate and provide some examples of the rock source.
Answer:
All aggregate (and soils) come from rock, which is a natural material of mineral grains
connected by strong permanent chemical bonds. Rocks are subject to breakdown by physical
(mechanical) and chemical processes when exposed to the elements. The souse rocks
include:
Igneous rock, which is excellent for construction purposes and includes granite, basalt,
etc.
Sedimentary rock, which has relatively good engineering properties and includes
sandstone, limestone, etc.
Metamorphic rock, which can have excellent engineering properties, like igneous rock.
3. Discuss some advantages and disadvantages of aggregate use.
Answer:
Advantages:
Provides structural stability and improved drainage when used as a base for roads
(both flexible and rigid payment) and buildings.
Aggregate is easier to compact; it is insensitive to the presence of water; it is not
susceptible to frost action in cold regions; and it is relatively incompressible.
As part of a composite material in concrete or asphalt, aggregate can greatly lower the
overall cost since aggregate can make up over 80% in concrete and as much as 95%
in asphalt.
When used as a filter to remove particles from water, aggregate can afford many
advantages over synthetic filters, including reduced cost, reduced environmental
impact, etc.
Disadvantages
When used as a base for infrastructure projects, site preparation may add significant
cost and time to complete the project.
In the case of asphalt and concrete, depending on the quality of the aggregate it may
lower the strength.
4. Describe the methods by which aggregates can be classified.
Answer:
Aggregate can be classified by size, source, and weight.
, Size: fine aggregate with particle sizes from 0.0029 inches to 3/16 inches and coarse
aggregate with particle sizes from 3/16 inches to 3.0 inches.
Source: natural aggregate is typically dredged from river and lake bottoms or
excavated from pits or quarries; manufacturedfrom various synthetic materials that
can be considered waste, such as crushed air-cooled blast furnace slag; and recycled,
which is considered synthetic because the parent material is derived from crushing
inert construction, demolition, and other waste materials.
Weight: classified into three categories based on its unit weight (bulk density):
o Normal weight aggregate with bulk unit weight (in pounds per cubic foot, pcf)
from 75 to 110 and specific gravity between 2.4 and 2.8,
o Lightweight aggregate with bulk unit weight from 35-pcf to 70-pcf and
specific gravity less than 2.4,
o Heavyweight aggregate with bulk unit weight greater than 130-pcf and
specific gravity greater than 2.8.
5. Provide three reasons why natural aggregate is different from manufactured aggregate.
Answer:
Natural aggregate is typically dredged from river and lake bottoms or excavated from
pits or quarries.
Natural aggregate can be created by crushing various types of rock (hard rock for
gravel and friable sandstone for sand).
Natural aggregate is not produced by synthetic means.
6. List three waste products that can be used as recycled aggregates.
Answer:
Construction or demolition waste
Crushed concrete derived from construction or demolition waste.
Scrap tires and glass
7. How are aggregates classified as coarse or fine?
Answer:
Fine aggregate with particle sizes from 0.0029 inches to 3/16 inches.
Coarse aggregate with particle sizes from 3/16 inches to 3.0 inches.
8. Explain the difference between density and specific gravity.
Answer:
Density is the mass per unit volume of a material and is expressed in units of g/cm3 or lb/ft3;
whereas specific gravity (also known as relative density) is the ratio of density of a material
to the density of water and is dimensionless.
9. Explain the difference between oven dry specific gravity, saturated surface dry specific
gravity, and the apparent specific gravity.
Answer:
Oven dry specific gravity is the oven dry density divided by the density of water.
Oven dry density is the weight of solid portion of an aggregate divided by the volume
of the aggregate particle, which includes the solid volume plus the volume of
permeable and impermeable pores of the aggregate.
, Saturated surface dry specific gravityis the saturated surface dry density divided by
the density of water. Saturated surface dry density is the weight of solid plus the
weight of water within the permeable pores of the aggregate particledivided by the
bulk volume of an aggregate particle, which includes the solid matter plus the volume
of permeable and impermeable pores.
Apparent specific gravity is the apparent density divided by the density of water.
Apparent density is the weight of the solid portion of an aggregate divided by the
volume of the aggregate particle, which only includes the solid portion and the
impermeable pores (i.e., it does not include permeable pores).
10. Describe three types of grading in aggregate and explain how their gradation charts would
differ. What is the preferred gradation type of an aggregate in Portland cement concrete and
why?
Answer:
Well-Graded. A well-graded aggregate is one where the aggregate sizes are present in
approximately equal proportions. A well-graded gradation chart will appear linear (i.e.,
with a constant slope).
Uniform. A uniform gradation means that a large quantity of the particles is approximately
the same size, which will result in a gradation curve that is nearly vertical near the sieve
numbers where the most weight is retained.
Gap-Graded. A gap-graded aggregate is one where most aggregates are large or small, and
very few particles of an intermediate size are present. A gradation chart is nearly horizontal
at the sieve number for the gap (or skipped) aggregate size.
The preferred gradation type of an aggregate in Portland cement concrete is well-graded
because the distribution of particle sizes will result in a low presence of voids since small
particles will fill those voids.
11. An acquired sample of fine aggregate was weighed with an initial mass of 549-g. The table
below provides a list of sieves used in the analysis and the weight of particles retained on
each sieve.
a) Determine the percent retained and the cumulative percent retained on each sieve.
b) Plot the gradation curve for the fine aggregate test sample. Describe the type of
gradation of the sample.
c) Calculate the fineness modulus of the test sample.
Sieve Analysis Data
Sieve Weight of
Opening Particles
Sieve Size Retained on each
Size (mm) Sieve, w (g)
3/8 in 9.50 0.0
#4 4.76 16.0
#8 2.36 35.4
#16 1.18 75.3
, #30 0.6 169.5
#50 0.3 156.2
#100 0.15 52.5
#200 0.074 28.9
Pan -- 13.2
Answer:
Sieve Analysis Data and Calculation Results.
Sieve Weight of Weight Fraction %
Opening Particles Retained on Cumulative
Sieve Size Retained on Each Sieve, W Retained, %Passin
Size (mm) each Sieve, w(g) (%) CW g, WP
3/8 in 9.50 0.0 0.0% 0.0% 100%
#4 4.76 16.0 2.9% 2.9% 97.1%
#8 2.36 35.4 6.5% 9.4% 90.6%
#16 1.18 75.3 13.8% 23.2% 76.8%
#30 0.6 169.5 31.0% 54.2% 45.9%
#50 0.3 156.2 28.6% 82.8% 17.3%
#100 0.15 52.5 9.6% 92.4% 7.7%
#200 0.074 28.9 5.3% 97.7% 2.4%
Pan -- 13.2 2.4% 100% 0.0%
i) Calculate the weight fraction of aggregates retained on each sieve.
The weight fraction retained on a sieve, Wsieve, is calculated as the weight of particles retained
on the sieve divided by the final total weight of all aggregate particles,
𝑤𝑠𝑖𝑒𝑣𝑒
𝑊𝑠𝑖𝑒𝑣𝑒 =
𝑤𝑓,𝑡𝑜𝑡𝑎𝑙
The calculation is demonstrated for the #4, #8, and #16 sieves, which are on rows 2, 3, and 4
respectively. The resulting percentage of aggregate particles retained on each sieve are
shown in the fourth column.
16
# 4 Sieve: 𝑊#4 = = 0.029 = 2.9%
547
35.4
#8 Sieve: 𝑊#8 = = 0.065 = 6.5%
547
75.3
#16 Sieve: 𝑊#16 = = 0.138 = 13.8%
547
ii) Calculate the cumulative percentage weight retained on each sieve.
The cumulative percentage weight retained, CWsieve, is the fraction of the aggregate weight
that does not pass a specific sieve. It is calculated by summing the weight fraction, Wsieve,
retained on a particular sieve plus the weight fraction retained on each of the sieves above, or
larger than the sieve of interest. The cumulative weight percentage retained on each sieve is
simply a running total of weight fractions. To illustrate the calculation, the cumulative
percent weight retained, CWsieve, on sieves #8, #16, and #30 are calculated as follows:
