CE 223
Construction Materials and Testing
Topic 2: AGGREGATES
Topic outline:
§ Uses of Aggregates
§ Sources
§ Types of Aggregates
CE 223 Construction Materials and Testing_Aggregates
Intended Learning Outcomes
After completing this course, the student must
be able to:
• Identify types of aggregates.
• Explain the use of aggregates and its properties.
CE 223 Construction Materials and Testing_Aggregates
AGGREGATES
Aggregates means a mass of crushed
stone,
gravel, sand, etc, predominantly
composed of individual particles.
CE 223 Construction Materials
and Testing_Aggregates
The 3 main uses of Aggregates in
civil engineering
1. As a Load Bearing
Material
§ an underlying material for
foundations and pavements
§ used to resist the overall
(static as well as dynamic)
load,
§ to distribute the load properly
to the supporting ground
§ and to drain the water off the
surface
CE 223 Construction Materials and Testing_Aggregates
The 3 main uses of Aggregates in
civil engineering
2. As a Filling Material
§ used for economy,
§ reduce shrinkage and
cracks
§ and to strengthen
the structure
§ used as riprap for
erosion protection
CE 223 Construction Materials and Testing_Aggregates
The 3 main uses of Aggregates in
civil engineering
3. As an Infiltrating
Material
§ used in water filtration
§ and sewage treatment
processes
§ ingredients in portland
cement and asphalt
concretes.
CE 223 Construction Materials and Testing_Aggregates
Uses of Aggregate in
Portland Cement Concrete
Ø Increases
the volume of concrete, thus
reduces the cost. Aggregates account for 6075% of the volume of concrete and 79-85%
weight of PCC.
Ø To provide a rigid structure.
Ø To reduce the shrinkage and cracking.
Ø Concrete aggregate is used in many
structures and substructures e.g. different
elements of a Building, bridges, foundations.
CE 223 Construction Materials and Testing_Aggregates
Uses of Aggregate in
Portland Cement Concrete
Ø
The smaller the aggregate size the greater its
surface area and the more binding material
(cement) will be required, resulting in a higher cost.
Ø
The greater the aggregate size the larger will be the
voids, resulting in wastage of binding material
(cement).
Ø
Hence a mixture of coarse and fine aggregate is
used in concrete to avoid both these problems.
CE 223 Construction Materials and Testing_Aggregates
Uses of Aggregate in
Asphalt Concrete
• Aggregates constitute 75% to 85% of the volume
and 92% to 96% of the mass. The asphalt
cement acts as a binder to hold the aggregates
together, but does not have enough strength to
lock the aggregate particles into position.
• As a result, the strength and stability of asphalt
concrete depends mostly on interparticle friction
between the aggregates and, to a limited extent,
on the binder.
CE 223 Construction Materials and Testing_Aggregates
General size characteristics of
aggregates
Fine aggregates
• Sand and/or crushed
stone
• < 4.75 mm sieve (No. 4).
Coarse aggregates
• Gravel and crushed stone
• > 4.75 mm sieve (No. 4).
A 4.75 mm sieve has openings
equal to 4.75 mm between the sieve
wires. A No. 4 sieve has four openings
CE 223 Construction Materials and Testing_Aggregates
per linear inch.
Sources
1.Natural sources for aggregates include gravel pits, river run
deposits, and rock quarries.
Gravel comes from pits and river deposits
Crushed stones result of processing rocks from quarries.
Usually, gravel deposits must also be crushed to obtain the needed
size distribution, shape, and texture
2.Manufactured aggregates can use slag waste from iron and steel
mills and expanded shale and clays to produce lightweight
aggregates.
Heavyweight concrete, used for radiation shields, can use steel slag
and bearings for the aggregate.
Lightweight concrete used for insulation. e.i Styrofoam beads as
aggregate
Natural lightweight aggregates include pumice, scoria, volcanic
cinders, tuff, and diatomite.
CE 223 Construction Materials and Testing_Aggregates
Types of Aggregates
Three General
Classification
1. Geological
2. Physical
3. Chemical
CE 223 Construction Materials and Testing_Aggregates
1. Geological Classification
(i) Igneous Rocks:
Ø These rocks are formed by cooling and
solidifying of the rock masses from their molten
magmatic condition of the material of the earth.
Ø Generally igneous rocks are strong and durable.
Ø Granite, trap and basalt are the rocks belonging
to this category. Granites are formed by slow
cooling of the lava under thick cover on the top.
Hence they have crystalline surface. The cooling
of lava at the top surface of earth results into
non-crystalline and glassy texture.
CE 223 Construction Materials and Testing_Aggregates
1. Geological Classification
(ii) Sedimentary Rocks:
Ø Due to weathering action of water, wind and frost
existing rocks disintegrates. The disintegrated material
is carried by wind (Aeolian) and water (Alluvial).
Ø Flowing water deposits its suspended materials at
some points of obstacles to its flow. These deposited
layers of materials get consolidated under pressure
and by heat. Chemical agents also contribute to the
cementing of the deposits.
Ø The rocks thus formed are more uniform, fine grained
and compact in their nature. They represent a bedded
or stratified structure in general. These are sand
stones, lime stones, mud stones etc.
CE 223 Construction Materials and Testing_Aggregates
1. Geological Classification
(iii) Metamorphic Rocks:
Ø Previously formed igneous and sedimentary
rocks undergo changes due to metamorphic
action of pressure and internal heat.
Ø For example due to metamorphic action
granite becomes greisses,
trap and basalt change to schist and laterite,
lime stone changes to marble,
sand stone becomes quartzite and
mud stone becomes slate.
CE 223 Construction Materials and Testing_Aggregates
2. Physical Classification
(i) Stratified Rocks:
Ø These rocks are having layered structure.
They possess planes of stratification or
cleavage.
Ø They can be easily split along these planes.
Ø Sand stones, lime stones, slate etc.
CE 223 Construction Materials and Testing_Aggregates
2. Physical Classification
(ii) Unstratified Rocks:
Ø These rocks are not stratified. They
possess crystalline and compact
grains.
Ø They cannot be split in to thin slab;
example Granite, trap, marble etc.
CE 223 Construction Materials and Testing_Aggregates
2. Physical Classification
(iii) Foliated Rocks:
Ø These rocks have a tendency to split along
a definite direction only.
Ø The direction need not be parallel to each
other as in case of stratified rocks.
Ø This type of structure is very common in
case of metamorphic rocks.
CE 223 Construction Materials and Testing_Aggregates
3. Chemical Classification
(i) Silicious rocks:
Ø The main content of these rocks is silica.
Ø They are hard and durable.
Ø Examples of such rocks are granite, trap, sand
stones etc.
CE 223 Construction Materials and Testing_Aggregates
3. Chemical Classification
(ii) Argillaceous rocks:
ØThe main constituent of these rocks is argil
i.e., clay.
ØThese stones are hard and durable but
they are brittle.
Ø They cannot withstand shock. Slates and
laterites are examples of this type of rocks.
CE 223 Construction Materials and Testing_Aggregates
3. Chemical Classification
(iii) Calcareous rocks:
Ø The main constituent of these rocks is
calcium carbonate.
ØLimestone is a calcareous rock of
sedimentary origin while marble is a
calcareous rock of metamorphic origin.
CE 223 Construction Materials and Testing_Aggregates
• Aggregates should be clean and able to bond
to the cement paste. If materials such as clay
are stuck to the aggregate surface cement
paste will not bond to the stone and the
strength of the mix will be compromised.
• Aggregate should not have excessive dust
coatings, which can reduce the bond between
cement and stones and increase water
demand.
• Other undesirable ingredients include pyrite,
coal and sulphate. If pyrite is in aggregate it
can decompose and this results in staining of
the concrete surface.
CE 223 Construction Materials and Testing_Aggregates
• Coal and lignite may swell during
the life of a structure and they
sometimes decompose; this can
leave voids in the concrete.
• Some aggregates are susceptible
to alkali aggregate reaction. These
aggregates contain particular
silicates which can react with the
alkalis produced when cement
hydrates.
• Fortunately, this occurrence is rare,
but when it occurs, because the
reaction is expansive, the concrete
can spall and crack.
CE 223 Construction Materials and Testing_Aggregates
REFERENCES:
• https://www.aboutcivil.org/uses-of-aggregate.html
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Allen, E & Iano J. (2009),Fundamentals of Building Construction Materials &
Methods, 5th Edition, John Wiley & Sons, Inc., Hoboken, New Jersey
Bhavikatti, S.S. (2010), Basic Civil Engineering, New Age International (P)
Limited, Publishers
Duggal, S.K.(2008), Building Materials, 3rd Edition, New Age International (P)
Limited, Publishers
Goncalves, M.C. and Margarido F. (2015), Materials for Construction and Civil
Engineering Science, Processing, and Design, Springer International
Publishing Switzerland
Kett,I. (2000),Engineered Concrete Mix Design and Test Methods, CRC Press
LLC
LABTEST Material Testing Equipment
Mamlouk, M.S. & ZaniewSki, J.P.(2017), Materials for Civil and Construction
Engineers, 4th Edition, Pearson
Merritt, F.S. & Ricketts J.T., Building Design and Construction Handbook, 6th
Edition, McGraw-Hill
CTTO: Pictures
Prepared & Presented by:
Engr. BERNADETH V. DAPUN
CE 223 Construction Materials and Testing_Aggregates