Steel is a versatile building material that can be manufactured in various forms like sections, bars, plates, and sheets to serve both structural and non-structural purposes in construction. Different types and grades of steel like mild steel, high carbon steel, high tensile steel, and reinforced bars have specific chemical compositions and mechanical properties making them suitable for uses like building frames, reinforcement, tools, and machine parts. Rolled sections, bars, plates, and sheets are designated according to their dimensions, weight, and other specifications to uniquely identify the type and size of each steel product.

1. Building Construction Materials
Steel
Mr. K. R. Patil
Assistant Professor
Department of Civil Engineering
D. Y. Patil College of Engineering &
Technology, Kolhapur

2. Steel
• Steel is the most suitable building material among metallic materials.
• This is due to a wide range and combination of physical and
mechanical properties of steel.
• By suitably controlling the carbon content and heat treatment, a desired
combination of hardness, ductility and strength can be obtained in steel.
• Properties and uses of various types of steel
1. Mild steel
• Mild steel is also known as low carbon or soft steel.
• It is ductile, malleable, tougher and elastic.
• It rusts quickly.
• Carbon content –0.15 – 0.3 %
• Ultimate tensile strength – 600 - 800 N/mm2
• Mild steel is used in the form of rolled sections, reinforcing bars, roof
coverings, sheet piles and in railway tracks.

3. 2. High carbon steel
• It is also known as hard steel. It is tougher and more elastic than mild
steel.
• Carbon content –0.6 – 0.8 %
• Ultimate tensile strength – 1400 - 2000 N/mm2
• High carbon steel is used for reinforcing cement concrete and
prestressed concrete members. It is also used for making tools and
machine parts.
3. High tensile steel
• It is a medium carbon steel. It is also known as high strength steel.
• Carbon content –0.55 – 1.5 %
• Ultimate tensile strength – 2000 N/mm2
• Minimum elongation – 10 %
• High tensile steel is used in prestressed concrete construction.

4. • Rolled Steel Sections
• Structural steel can be rolled into various shapes and sizes in rolling
mills. I.S. Hand Book No. 1 published by Bureau of Indian Standards
provides the dimensions, weights and geometrical properties of
various sections.
Rolled steel I-sections ( Fig. a)
Rolled steel channel sections ( Fig. b)
Rolled steel T-sections ( Fig. c)
Rolled steel angle-sections ( Fig. d)
Rolled steel tube-sections ( Fig. e)
Rolled steel bars ( Fig. f)
Rolled steel flats ( Fig. g)
Rolled steel plates
Rolled steel sheets

5. 1. An I-section is designated by its depth and weight.
• e.g. ISLB (Indian Standard Light Weight Beams) 500@735.7
N/m means, the I-section is 500 mm deep and its self weight is
735.7 N per metre length.
• A channel-section is designated by its depth and weight.
• e.g. ISLC (Indian Standard Light Weight Channels) 350@380.6
N/m means that the channel section is 350 mm deep and the self
weight is 380.6 N per metre length.
• A T-section is designated by its depth and weight.
• e.g. ISNT 125@268.8 N/m means that the Tee section is 125 mm
deep and the self weight is 268.8 N per metre length.
• An angle-section is designated by its leg length and thickness.
• e.g. ISA 40 x 25 x 6 mm means, the section is unequal angle with
legs 40 mm and 25 mm in length and thickness of legs 6 mm.

6. • Steel tubes are designated by their outside diameter and self weight.
• Steel flats are designated by width and thickness of the section.
• e.g. 30 ISF 10 mm means the flat is 30 mm wide and 10 mm thick.
• Steel plates are designated by length, width and thickness of the
section.
• e.g. ISPL 2000 mm x 1000 mm x 8 mm means the plate is 2000 mm
long, 1000 mm wide and 8 mm thick.
• Steel sheets are designated by length, width and thickness of the
section.
• e.g. ISSH 2000 mm x 600 mm x 4 mm means the sheet is 2000 mm
long, 600 mm wide and 4 mm thick.
• Round bars are generally used as reinforcement in reinforced concrete
structures.
• Round bars and square bars are also used for decorative purposes and
grills for windows, fencing, parapets, etc.

7. • Reinforcing steel bars
• Cement concrete is most commonly used construction material throughout the
world.
• Concrete is very good in compression but is extremely weak in tension.
• To overcome this weakness, steel reinforcement is required. Steel
reinforcement is available in the form of bars of specific diameters with
different chemical composition like mild steel and high tensile strength.
• Types and grades of reinforcing bars
• High yield strength deformed (HYSD) bars
• These bars have ribs or deformations on the surface, which prevent longitudinal
movement of the bar relative to the surrounding concrete.
• Thus, the deformed surface ensures better bond between reinforcement and
concrete. HYSD bars result in a considerable increase in yield, tensile and bond
strength when twisted hot or cold.
• Cold twisted deformed (CTD) bars are most suitable for construction purpose
and are widely used in India. CTD bars with trademark TOR are called Tor-
steel.
• Tor steel is high strength deformed bars with high yield and bond strength. CTD
bars are available in Fe-415 grade.

8. • Thermo-mechanically treated (TMT) bars
• These are extra high strength bars, which eliminate cold twisting. In
this process, the steel bars receive a short intensive cooling as they pass
through a water cooling system after the last rolling mill stand. The
reduction in temperature converts the surface layer into a hardened
structure.
• TMT bars can be used for general concrete reinforcement in buildings,
bridges and various other concrete structures. They are highly
recommended for use in high-rise buildings because of saving in steel
due to the higher strength.
• TMT bars are available in TMT 415, TMT 500 and TMT 550 types.
Here the number indicates minimum yield strength in N/mm2.
• The latest development in reinforcing bars is thermo-mechanically
treated high-strength corrosion resistant (TMT-HCR) bars. These bars
have superior resistance to aggressive weather conditions. TMT-HCR
bars are widely used in coastal and marine environments which are
susceptible too corrosion, bridges, dams, industrial structures, high rise
buildings and underground structures.

9. • Uses of Steel:
• Structural material in trusses, stanchions, beam in the form of various
sections.
• Non structural components for grills, stairs, windows & doors.
• In fabrication of steel pipes, tubes, tanks, ducts etc.
• Used as corrugated sheets which act as roof over the structures.
• Mild steel is used as distribution steel in R.C.C. members.
• Tor steel is used as main steel in R. C. C. members.
• High tensile steel cables are used in prestressed concrete girders.