STEEL
-
The use of cast iron dates back to about 1500 B.C, when primitive furnaces were used to heat
the ore in a charcoal fire.
-
Ferrous metals were produced on a relatively small scale until the blast furnace was developed
in the 18th century.
-
Iron products were widely used in the latter half of the 18th century and the early part of the 19th
century. Steel production started in mid-1800s, when the Bessemer converter was invented.
-
In the second half of the 19th century, steel technology advanced rapidly due to the development
of the basic oxygen furnace and continuous casting methods.
-
More recently, computer-controlled manufacturing has increased the efficiency and reduced
the cost of steel production.
CLASSIFICATION OF METALS
1. FERROUS METALS
-
A ferrous material is the one in which iron is a main constituent. Iron ore is first converted into
pig iron and then pig iron is subjected to various metallurgical processes to mix different
percentage of carbon and to get the following three useful ferrous materials:
1. Cast iron – carbon content 1.7% to 4.5%
2. Wrought iron – carbon content 0.05% to 0.15%
3. Steel – carbon content 0.15% to 0.25%
-
All ferrous materials contain about 0.5 to 3% silica, less than 2% manganese, 0.15% sulphur,
and 0.6% phosphorous.
1. Cast Iron:
Properties of Cast Iron
a) Compression strength is 700 N/mm² and tensile strength is 150 N/mm²
b) It is brittle and does not absorb shocks
c) Its specific gravity is 7.5
d) Its structure is coarse, crystalline, and fibrous
e) It cannot be magnetised
f) It does not rust easily
g) It has low melting point of about 1200°C
Uses of Cast Iron:
1. It is used for making rain water and sanitary pipes, sanitary fittings and manhole covers.
2. It is used for making railings and spiral stair cases
3. Fire gratings, cover for pumps and motors and brackets are made with cast irons
2. Wrought Iron: It is almost pure iron. It contains less than 0.15% carbon. Attempts are made
to reduce the other impurities during the process of manufacturing.
Properties of Wrought Iron
1. Its ultimate compressive strength is 200 N/mm² and ultimate tensile strength is 375 N/mm²
2. It is ductile and brittle
3. Its unit weight is 77 kN/m³
4. It melts at about 1500°C. It becomes so soft at 900°C that two pieces can be joined by
hammering
5. It can be absorbs shocks very well
6. It forms temporary magnets but it cannot be magnetised permanently
7. It rust more easily
Uses of Wrought Iron
1. It is used for making nails nuts and botts, wires and chains
2. It is used for making roofing sheets, grills, fences, window gaurds etc.
3. Steel: It is used extensively used building material. The following three varieties of steel are
extensively used:

a) Mild steel

b) High carbon steel and

c) High tensile steel
a) Mild Steel: it contains a maximum of 0.25% carbon, 0.055% of sulphur and 0.55% of
phosphorus.
Properties of Mild Steel
1. It is malleable and ductile
2. It is more elastic
3. It can be magnetised permanently
4. Its specific gravity is 7.8
5. Its young's modulus is 2.1 x 10⁵ N/mm²
6. It can be welded easily
7. It is equally strong in tension and in compression
b) High Carbon Steel: The carbon contains in this steel is 0.7% to 12.5%
Properties of Carbon Steel
1. It is more tough and elastic compared to mild steel
2. Wielding is difficult
3. It can be magnetised permanently
4. It is stronger in compression than in tension
5. It withstands shocks and vibrations better
Uses of High Carbon Steel
1. It is used for making tools such as drills, files, chisels
2. Many machine parts are made with high carbon steel since it is capable of
withstanding
3. shocks and vibrations
c) High Tensile Steel: It contains 0.8% carbon and 0.6% manganese. The strength of
this steel is quite high. High tensile steel wires are used in prestressed concrete works.
CONSTRUCTION CALSSIFICATION OF STEEL PRODUCTS:
1. Structural steel (vertical columns) produced by continuous casting and hot rolling for large
structural shapes, plates, and sheet steel
2. Cold-formed steel (trusses and decking) produced by cold-forming of sheet steel into
desired shapes
3. Fastening products used for structural connections, including bolts, nuts and washers
4. Reinforcing steel (rebars) for use in concrete reinforcement
5. Miscellaneous products for use in such applications as forms and pans
STEEL PRODUCTION
Three phases of steel production process:
1. Reducing iron ore to pig iron
2. Refining pig iron (and scrap steel from recycling) to steel
3. Forming the steel into products
CONVERSION OF RAW MATERIAL INTO DIFFERENT STEEL SHAPES
HEAT TREATMENT OF STEEL
1. ANNEALING
The objectives of annealing are to refine the grain, soften the steel, remove internal stresses,
remove gases, increase ductility and toughness, and change electrical and magnetic properties.
Four types of annealing can be performed, depending on the desired results of the heat
treatment:

Full annealing requires heating the steel to about 50°C above the austenitic temperature
line and holding the temperature until all the steel transforms into either austenite or
austenite–cementite, depending on the carbon content.

Process annealing is used to treat work-hardened parts made with low carbon steel (i.e.,
less than 0.25% carbon). The material is heated to about 700°C and held long enough to
allow recrystallization of the ferrite phase.

Stress relief annealing is used to reduce residual stresses in cast, welded, and coldworked parts and cold-formed parts. The material is heated to 600 to 650°C, held at
temperature for about 1 hour, and then slowly cooled in still air.

Spheroidization is an annealing process used to improve the ability of high carbon (i.e.,
more than 0.6% carbon) steel to be machined or cold worked. It also improves abrasion
resistance. The cementite is formed into globules (spheroids) dispersed throughout the
ferrite matrix.
2. NORMALIZING
Normalizing is similar to annealing, with a slight difference in the temperature and the rate of
cooling. Steel is normalized by heating to about 60°C above the austenite line and then cooling
under natural convection. The material is then air cooled. Normalizing produces a uniform, finegrained microstructure.
3. HARDENING
Steel is hardened by heating it to a temperature above the transformation range and holding it
until austenite is formed. The steel is then quenched (cooled rapidly) by plunging it into, or
spraying it with, water, brine, or oil. The rapid cooling changes the grain structure forming
martensite rather than allowing the transformation to the ferrite BCC structure.
4. TEMPERING
The predominance of martensite in quench-hardened steel results in an undesirable brittleness.
Tempering is performed to improve ductility and toughness. Martensite is a somewhat unstable
structure. Heating causes carbon atoms to diffuse from martensite to produce a carbide
precipitate and formation of ferrite and cementite. After quenching, the steel is cooled to about
40°C then reheated by immersion in either oil or nitrate salts. The steel is maintained at the
elevated temperature for about 2 hours and then cooled in still air.
STEEL ALLOYS

Alloy metals can be used to alter the characteristics of steel. By some counts, there are as many
as 250000 different alloys of steel produced.
Alloy agents are added to improve one or more of the following properties:
1. hardenability
2. corrosion resistance
3. machinability
4. ductility
5. strength
COMMON STEEL ALLOYING AGENTS:
STRUCTURAL STEEL
Structural steel is used in hot-rolled structural shapes, plates, and bars.
Structural steel is used for various types of structural members, such as columns, beams, bracings,
frames, trusses, bridge girders, and other structural applications.
1. STRUCTURAL STEEL GRADES
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Due to the widespread use of steel in many applications, there are a wide variety of systems for
identifying or designating steel, based on grade, type and class.
-
Virtually, every country with an industrial capacity has specifications for steel.
- In the United States, there are several associations that write specifications for steel, such as
the Society of Automotive Engineers, SAE, the American Iron and Steel Institute, AISI, and the
American Society for Testing and Materials, ASTM.
2. SECTIONAL SHAPES
These shapes are produced in different sizes and are designated with the letters W, HP, M, S,
C, MC, and L.
W shapes are doubly symmetric wide-flange shapes whose flanges are substantially parallel.
HP shapes are also wide-flange shapes whose flanges and webs are of the same nominal
thickness and whose depth and width are essentially the same.
The S shapes are doubly symmetric shapes whose inside flange surfaces have approximately
16.67% slope.
The M shapes are doubly symmetric shapes that cannot be classified as W, S, or HP shapes.
C shapes are channels with inside flange surfaces having a slope of approximately 16.67%.
MC shapes are channels that cannot be classified as C shapes.
L shapes are angle shapes with either equal or unequal legs. In addition to these shapes, other
structural sections are available, such as tee, sheet piling, and rail.
ASTM STRUCTURAL SHAPES
MECHANICAL TESTING OF STEEL
1. TENSION TEST
The tension test (ASTM E8/E8M) on steel is performed to determine the yield strength, yield
point, ultimate (tensile) strength, elongation, and reduction of area. Typically, the test is
performed at temperatures between 10°C and 35°C.
 Several cross-sectional shapes are permitted, such as round and rectangular, as shown in
Figure 3.15. Plate, sheet, round rod, wire, and tube specimens may be used.
 A 12.5 mm diameter round specimen is used in many cases. The gauge length over which the
elongation is measured typically is four times the diameter for most round-rod specimens.
 An extensometer with a dial gauge LVDT (Figure 1.31) is used to measure the deformation of
the entire gauge length.
 The test is performed by applying an axial load to the specimen at a specified rate. Figure 3.16
shows a tensile test being performed on a round steel specimen using an LVDT extensometer
to measure the deformation.
2. TORSION TEST

The torsion test (ASTM E143) is used to determine the shear modulus of structural materials.

The shear modulus is used in the design of members subjected to torsion, such as rotating
shafts and helical compression springs. In this test, a cylindrical, or tubular, specimen is loaded
either incrementally or continually by applying an external torque to cause a uniform twist within
the gauge length.
 The amount of applied torque and the corresponding angle of twist are measured throughout
the test. Figure 3.21 shows the shear stress–strain curve.
 The shear modulus is the ratio of maximum shear stress to the corresponding shear strain
below the proportional limit of the material, which is the slope of the straight line between R (a
pretorque stress) and P (the proportional limit).
3. CHARPY V NOTCH IMPACT TEST
The Charpy V Notch impact test (ASTM E23) is used to measure the toughness of the material or
the energy required to fracture a V-notched simply supported specimen.
 The test is used for structural steels in tension members. The standard specimen is 55 * 10 *
10 mm with a V notch at the center of one side, as shown in Figure 3.22. Before testing, the
specimen is brought to the specified temperature for a minimum of 5 minutes in a liquid bath or
30 minutes in a gas medium. The specimen is inserted into the Charpy V notch impact-testing
machine (Figure 3.23) using centering tongs.
4. BEND TEST
The ductility to accommodate bending is checked by performing the semi guided bend test (ASTM
E290).
 The test evaluates the ability of steel, or a weld, to resist cracking during bending. The test is
conducted by bending the specimen through a specified angle and to a specified inside radius
of curvature.
 When complete fracture does not occur, the criterion for failure is the number and size of cracks
found on the tension surface of the specimen after bending.
5. HARDNESS TEST
Hardness is a measure of a material’s resistance to localized plastic deformation, such as a small
dent or scratch on the surface of the material.
 A certain hardness is required for many machine parts and tools. Several tests are available to
evaluate the hardness of materials. In these tests, an indenter (penetrator) is forced into the
surface of the material with a specified load magnitude and rate of application. The depth, or the
size, of the indentation is measured and related to a hardness index number.

One of the methods commonly used to measure hardness of steel and other metals is the
Rockwell hardness test (ASTM E18).

In this test, the depth of penetration of a diamond cone, or a steel ball, into the specimen is
determined under fixed conditions (Figure 3.26).
6. ULTRASONIC TESTING

Ultrasonic testing is a nondestructive method for detecting flaws in materials. It is particularly
useful for the evaluation of welds. During the test, a sound wave is directed toward the weld
joint and reflected back from a discontinuity, as shown in Figure 3.27.
 A sensor captures the energy of the reflected wave and the results are displayed on an
oscilloscope. This method is highly sensitive in detecting planar defects, such as incomplete
weld fusion, delamination, or cracks (Hassett, 2003).
WELDING
 Many civil engineering structures such as steel bridges, frames, and trusses require welding
during construction and repair. Welding is a technique for joining two metal pieces by applying
heat to fuse the pieces together.
 A filler metal may be used to facilitate the process. The chemical properties of the welding
material must be carefully selected to be compatible with the materials being welded.
 A variety of welding methods are available, but the common types are arc welding and gas
welding.
 Other types of welding include flux-cored arc welding, self-shielded flux arc welding, and
electroslag welding (Frank and Smith, 1990)
STEEL CORROSION
 Corrosion is defined as the destruction of a material by electrochemical reaction to the
environment. For simplicity, corrosion of steel can be defined as the destruction that can be
detected by rust formation.
 Corrosion of steel structures can cause serious problems and embarrassing and/or dangerous
failures. For example, corrosion of steel bridges, if left unchecked, may result in lowering weight
limits, costly steel replacement, or collapse of the structure.
 Other examples include corrosion of steel pipes, trusses, frames, and other structures. It is
estimated that the cost of corrosion of the infrastructure in the United States alone is $22.6 billion
each year (corrosion costs web site, 2009).
 The infrastructure includes (1) highway bridges, (2) gas and liquid transmission pipelines, (3)
waterways and ports, (4) hazardous materials storage, (5) airports, and (6) railroads.
 Corrosion is an electrochemical process; that is, it is a chemical reaction in which there is transfer
of electrons from one chemical species to another.
 In the case of steel, the transfer is between iron and oxygen, a process called oxidation
reduction.
 Corrosion requires the following four elements (without any of them corrosion will not occur):
1. an anode—the electrode where corrosion occurs
2. a cathode—the other electrode needed to form a corrosion cell
3. a conductor—a metallic pathway for electrons to flow
4. an electrolyte—a liquid that can support the flow of electrons
METHODS FOR CORROSION RESISTANCE
 Since steel contains three of the four elements needed for corrosion, protective coatings can be
used to isolate the steel from moisture, the fourth element.
There are three mechanisms by which coatings provide corrosion protection (Hare, 1987):
1. Barrier coatings work solely by isolating the steel from the moisture. These coatings have low
water and oxygen permeability.
2. Inhibitive primer coatings contain passivating pigments. They are low-solubility pigments that
migrate to the steel surface when moisture passes through the film to passivate the steel surface.
3. Sacrificial primers (cathodic protection) contain pigments such as elemental zinc. Since zinc is
higher than iron in the galvanic series, when corrosion conditions exist the zinc gives up
electrons to the steel, becomes the anode, and corrodes to protect the steel. There should be
close contact between the steel and the sacrificial primer in order to have an effective corrosion
protection.
MECHANICAL PROPERTIES OF STEEL

Ultimate strength

High-temperature effects

Ductility

Hardness

Toughness

Fatigue resistance
ALUMINUM
 Aluminum is the most plentiful metal on Earth, representing 8% of its crust. Although plentiful,
aluminum exists primarily as oxides.
 The process of extracting aluminum from oxide is very energy intensive. In fact, approximately
2% to 3% of the electricity used in the United States is consumed in aluminum production.
 Of the 24 million tons of aluminum produced annually, approximately 75% is from ore reduction
and 25% is from recycled materials.
In terms of the amount of metal produced, aluminum is second only to steel.

About 25% of aluminum produced is used for containers and packaging; 20% for architectural
applications, such as doors, windows, and siding; and 10% for electrical conductors.
CHARACTERISTICS OF ALUMINUM
The advantages of aluminum are that it (Budinski and Budinski, 2010)

has one-third the density of steel

has high reflectivity

has good thermal and electrical conductivity

can be die cast

has high strength-to-weight ratio

is easily machined

can be given a hard surface by anodizing and

has good formability
hard coating

is nonmagnetic

has alloys that are weldable

is nontoxic

will not rust
PRODUCTION OF ALUMINUM
USES OF ALUMINUM
1. It is used to make door and window frames.
2. Aluminium structural members are becoming popular.
3. Aluminium wires are used as conductors of electricity.
4. It is used as a foil.
5. Aluminium powder serves as pigments in paints.
TYPES OF ALUMINUM ALLOYS
Two types of Aluminum Alloys: wrought and cast alloys.

Alloying elements enhance the physical properties of aluminum for specific purposes creates
these alloys.

Wrought aluminum alloys are designated using four-digit system, with the first digit specifying
the alloying element. The following table lists the major series including the alloying elements
and general uses for each series.
WELDING AND FASTENING
Aluminum pieces can be joined either by welding or by using fasteners.
WELDING
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requires that the tough oxide coating on aluminium be broken and kept from reforming during
welding, so arc welding is generally performed in the presence of an inert gas that shields the
weld from oxygen in the atmosphere.
The two common processes by which aluminium is welded are
1. gas metal arc welding, GMAW,
2. gas tungsten arc welding, GTAW.
-
GMAW process, the filler wire also serves as the electrode.
-
GTAW uses a tungsten electrode and a separate filler wire. Welding can alter the tempering of
the aluminium in the area of the weld.
-
For example, the tensile strength of 6061-T6 is 290 MPa, but the tensile strength of a weld in
this alloy is only about 165 MPa.
-
For design purposes, it is assumed the weld affects an area of 25 mm on each side of the weld.
FASTENING
Fasteners like bolts or rivets can join aluminum pieces.
-
Bolts can be either aluminum or steel. When steel bolts are used, they must be either
galvanized, aluminized, cadmium plated, or made of stainless steel to prevent the development
of galvanic corrosion.
- Rivet fasteners are made of aluminum and are cold driven. Both bolt and rivet joints are
designed based on the shear strength of the fastener and the bearing strength of the material
being fastened.
CORROSION
Aluminum develops a thin oxidation layer immediately upon exposure to the atmosphere. This tough
oxide film protects the surface from further oxidation.
The alloying elements alter the corrosion resistance of the aluminum.
The alloys used for airplanes are usually given extra protection by painting or “cladding” with a thin coat
of a corrosion-resistant alloy.
Painting is generally not needed for medium-strength alloys used for structural applications.
Galvanic corrosion occurs when aluminum is in contact with any of several metals in the presence of
an electrical conductor, such as water.
The best protection for this problem is to break the path of the galvanic cell by painting, using an
insulator, or keeping the dissimilar metals dry.
MASONRY

A masonry structure is formed by combining masonry units, such as stones, blocks, or brick,
with mortar.

One of the oldest construction materials. Pyramids of Egypt, Great wall of China, Greek and
Roman ruins.
Masonry units can be classified as

Concrete masonry units – can be either solid or hollow

Clay bricks – typically solid

Structural clay tiles – hollow units that are larger than clay bricks and are used for structural
and non-structural masonry applications, such as partition walls and filler panels.

Glass blocks – typically solid
 Stone – typically solid
1. CONCRETE MASONRY UNITS

Solid concrete units are commonly called concrete bricks.
 Hollow units are known as concrete blocks, hollow blocks, or cinder blocks. Hollow units
have a net cross-sectional area in every plane parallel to the bearing surface less than
75% of the gross cross-sectional area in the same plane. If this ratio is 75% or more, the
unit is categorized as solid (Portland Cement Association, 1991).
Concrete masonry units are manufactured in three classes, based on their density:
 Lightweight units – pumice, scoria, cinders, expanded clay and expanded shale are
used to manufacture lightweight units. Lightweight units have higher thermal and fire
resistance properties and lower sound resistance than normal weight units.
 Medium-weight units –
 Normal-weight units – well-graded sand, gravel, and crushed stone are used to
manufacture normal-weight units.
Concrete masonry units can be classified as

Load bearing (ASTM C90) and

Non – load bearing (ASTM C129).
Load-bearing units must satisfy a higher minimum compressive strength requirement than non–loadbearing units.
2. CLAY BRICKS
 are small, rectangular blocks made of fired clay. The clays used for brick making vary
widely in composition from one place to another. Clays are composed mainly of silica
(grains of sand), alumina, lime, iron, manganese, sulfur, and phosphates, with different
proportions. Bricks are manufactured by grinding or crushing the clay in mills and mixing
it with water to make it plastic. The plastic clay is then molded, textured, dried, and finally
fired. Bricks are manufactured in different colors, such as dark red, purple, brown, gray,
pink, or dull brown, depending on the firing temperature of the clay during manufacturing.
The firing temperature for brick manufacturing varies from 900°C to 1200°C. Clay bricks
have an average density of 2 Mg/m3.
Clay bricks are used for different purposes

Building bricks – (common bricks) are used as a structural material and are typically
strong and durable.

Facing bricks – are used for facing and aesthetic purposes and are available in different
sizes, colors, and textures.

Floor bricks – are used on finished floor surfaces and are generally smooth and dense,
with high resistance to abrasion.

Paving bricks – are used as a paving material for roads, sidewalks, patios, driveways,
and interior floors. Paving bricks are available in different colors, such as red, gray, or
brown, are typically abrasion resistant and could usually be vitrified (glazed to render it
impervious to water and highly resistant to corrosion).
MORTAR
 Mortar is a mixture of cementitious material, aggregate, and water. Mortar can be classified as
cement-lime mortar, cement mortar, or masonry cement mortar.
Mortar is used for the following functions:

bonding masonry units together, either non-reinforced or reinforced

serving as a seating material for the units

leveling and seating the units

providing aesthetic quality of the structure
 Mortar starts to bind masonry units when it sets. During construction, bricks and blocks should
be rubbed and pressed down in order to force the mortar into the pores of the masonry units to
produce maximum adhesion. It should be noted, however, that mortar is the weakest part of the
masonry wall. Therefore, thin mortar layers generally produce stronger walls than do thick layers.
 Since mortar is used as an adhesive and sealant, it is very important that it forms a complete,
strong, and durable bond with the masonry units and with the rebars that might be used to
reinforce masonry walls. The ability to bond individual units is measured by the tensile bond
strength of mortar (ASTM C952), which is related to the force required to separate the units. The
tensile bond strength affects the shear and flexural strength of masonry. The tensile bond
strength is usually between 0.14 and 0.55 MPa and is affected by the amount of lime in the mix.
 Other properties that affect the performance of mortar are workability, tensile strength,
compressive strength, resistance to freeze and thaw, and water retention.
GROUT
 Grout is a high-slump concrete consisting of portland cement, sand, fine gravel, water, and
sometimes lime.
 The minimum compressive strength of grout is 14 MPa at 28 days, according to ASTM C476.
Grout is used to fill the cores or voids in hollow masonry units for the purpose of
(1) bonding the masonry units,
(2) bonding the reinforcing steel to the masonry,
(3) increasing the bearing area,
(4) increasing fire resistance, and
(5) improving the overturning resistance by increasing the weight.
PLASTER
 Plaster is a fluid mixture of portland cement, lime, sand, and water, which is used for finishing
either masonry walls or framed (wood) walls.
 Plaster is used for either exterior or interior walls. Stucco is plaster used to cover exterior walls.
The average compressive strength of plaster is about 13.8 MPa at 28 days.
Other Sustainability Considerations

Abundance of raw materials

Efficient use of raw materials

Use of recycled materials

Recyclable

Sustainable measures in acquisition or

Salvageable
manufacture

Durable
Use of regionally available materials

Non-toxic
(near to the building project site)

Avoidance of construction waste.


Regional
manufacture
or fabrication
(near to the building project site)