Bars – Introduction , Types, Best One To Use 15, RCC-Steel Bars

Term Paper CIV 101 Elements of RCC Topic: - Bars – Introduction , Types, Best One To Use

Subbmitted To Mr. Amit Dhir

Subbmitted By Atish Kumar Roll No.:- 15 Class: - Diploma Civil Semester: - 5th

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Contents 1) Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . 3 2) Type of Steel Bars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3) Mild Steel Bar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4) Various Grades of Mild Steel Bars . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5) Deformed Steel Bars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 6) TMT Bars (Thermo Mechanically Treated Bars).. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 7) Features of TMT Bars. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8) HSD Steel Bars (High Strength Deformed Bars) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 9) Features of HSD Bars

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10) The strength of bonds of deformed bars. . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . 9 11) Steel Bars for RCC Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 12) General Precautions for Steel Bars in Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 13) Weight of Different Steel Bars. . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 14) Stainless Steel bars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 15) Best one to Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 16) Referance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

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Introduction A rebar, or reinforcing bar, is a common steel bar, and is commonly used in reinforced concrete and reinforced masonry structures. It is usually formed from carbon steel, and is given ridges for better mechanical anchoring into the concrete. It can also be described as reinforcement or reinforcing steel.

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Type of Steel Bars Generally there are two types of steel bars available in the market.

1. Mild steel bars 2. Deformed steel bars

Mild steel bars (as per IS: 432, part-I -1982) Mild steel bars are used for tensile stress of RCC (Reinforced cement concrete) slab beams etc. in reinforced cement concrete work. These steel bars are plain in surface and are round sections of diameter from 6 to 50 mm. These rods are manufactured in long lengths and can be cut quickly and be bent easily without damage.

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Various Grades of Mild Steel Bars Reinforcement bars in accordance with standard IS No. 432 part-I can be classified into following types. 1) Mild Steel Bars: Mild steel bars can be supplied in two grades a)Mild steel bars grade-I designated as Fe 410-S or Grade 60 b) Mild steel bars grade-II designated as Fe-410-o or Grade 40 2) Medium Tensile Steel Bars designated as Fe- 540-w-ht or Grade 75 Physical Requirement:

Grade II Mild steel bar are not recommended for use in structures located in earth quake zones subject to severe damage and for structures subject to dynamic loading (other than wind loading) such as railways and highways bridges. Every lot or consignment of mild steel bars brought at the site of work should be tested in laboratory before use in the work. However for small work one can use mild steel bars on the basis of verifying tests results made by manufacturer in his own laboratory; which are available with supplier. Some of manufacturers stamped MS bars grade with their make /name and also give certification of test and grade. On the basis of the above information you can store mild steel bars grade-wise at the site of work. 5

Deformed Steel Bars (as per IS: 1786-1985) As deformed bars are rods of steels provided with lugs, ribs or deformation on the surface of bar, these bars minimize slippage in concrete and increases the bond between the two materials. Deformed bars have more tensile stresses than that of mild steel plain bars. These bars can be used without end hooks. The deformation should be spaced along the bar at substantially uniform distances. To limit cracks that may develop in reinforced concrete around mild steel bars due to stretching of bars and some lose of bond under load it is common to use deformed bars that have projecting ribs or are twisted to improve the bond with concrete. These bars are produced in sections from 6 mm to 50 mm dia. In addition the strength of bonds of deformed bars calculated should be 40 to 80 % higher than that of plain round bars of same nominal size. And it has more tensile stress than that of plain round bars of same nominal size. Cold twisted deformed (Ribbed or Tor Steel Bars) bars are recommended as best quality steel bars for construction work by structural Engineer.

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TMT Bars (Thermo Mechanically Treated Bars) TMT Bars,Thermo mechanically treated bars are high strength deformed steel bars used in reinforced cement concrete (RCC) work manufactured with the help of advancement of technology. TMT bars are latest production in MS steel bars and have superior properties such as strength, ductility, welding ability, bending ability and highest quality standards at international level.

Features of TMT Bars         

Better ductility and malleability High yield strength and toughness More bonding strength Earthquake resistance Corrosion resistance High thermal resistance Economical and safe in use No loss in strength at welded joints Ordinary electrodes used for welding the joints

Caution  While purchasing TMT bars, notice identification mark on these bars from manufacturing firm.  For big projects it is advised to check that only one type/grade of bars is brought to the site and is used in the project after conducting test for each lot. Do not use mixed, 2 or 3 types/grades bars in RCC work at one work.

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HSD Steel Bars (High Strength Deformed Bars) High strength deformed bars IS: 1786-1985 are steel bars which are provided with lugs, ribs, projection or deformation on the surface and are produced in form of cold twisted deformed bars. These bars are extensively used for reinforcement purposes in a construction. Due to ribs or projections on the surface, these steel bars minimize slippage in concrete and increase the bond between two materials i.e. between cement concrete and steel bars. The deformed bars have more compressive and tensile stress than that of mild steel plain bars. High strength deformed bars have improved anchorage; therefore they can be used without end hooks or bent up ends of bars. This reduces labor for fabrication of steel reinforcement. The deformation is spaced on bar at uniform distances. These bars are produced in sizes or sections from 4 mm to 50 mm in diameter. Generally cracks develop in reinforced concrete around mild steel bars due to stretching of bars, loss of bond under the load. To minimize this problem, deformed bars having projecting ribs or twisted surface which improves the bond with the concrete should be used in RCC work.

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Features of HSD Bars 

Low carbon value:- HSD Bars have lower carbon level, resulting in good ductility, strength and welding ability.

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Superior bonding strength:- HSD bars are well known for their excellent bonding strength when used with concrete.

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Welding capability:- Since these bars have lower carbon content, they have 100%

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welding capability than conventional bars. High tensile strength:- HSD bars feature high tensile strength. They offer great asset in construction process, where a lot of bending and re bending is required.

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Wide application range :- These bars have wide application range like in building residential, commercial and industrial structures, bridges, etc.

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Satisfactorily malleability:- minimum weight and maximum strength and suitable for both compression and tension reinforcement.

The strength of bonds of deformed bars In addition, the calculated strength of bonds of deformed bars should be 40 to 80 % higher than that of plain round bars of same nominal size. Tor steel possesses the strength of 1.5 to 2.0 times of mild steel in compression as well as in tension, whereas it costs only 10% more than mild steel. Deformed steel bars have minimum 0.2% proof stress or yield stress in N/mm square. Proof stress is the stress at which non proportional elongation equal to 0.2% of the original gauge length takes place. Hence deformed steel bars are very economical to use in RCC work. Structural Engineer recommends cold twisted deformed (Ribbed or Tor Steel Bars) bars as they are best quality steel bars for construction work. Mechanical properties of high strength deformed (HSD) steel bars for concrete reinforcement

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Steel Bars for RCC Work All finished steel bars for reinforced work should be neatly rolled to the dimension and weights as specified. They should be sound, free from cracks, surface flaws, laminations, rough, jagged and imperfect edges and other defects. It should be finished in a work manlike manner.

Column made of steel bars

General Precautions for Steel Bars in Reinforcement           

Steel bars are clear, free from loose mil scales, dust and loose rust coats of paints, oil or other coatings which may destroy or reduce bond strength. Steel bars should be stored in such a way as to avoid distortion and to prevent deterioration and corrosion. Steel bars should not be clean by oily substance to remove the rust. The bar is bent correctly and accurately to the size and shape as shown in drawings. If possible, the bar of full length is used. Overlapping bars do not touch each other and these should be kept apart with concrete. The overlap if given should be staggered. The cranks in the bar at the end should be kept in position by using spots. The steel bars should not be disturbed while lying cements concrete. Required cover under steel bars should be given before laying the cement concrete. No overlap is given in the bar having a diameter more than 36 mm, if required, the bar should be welded.

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Weight of Different Steel Bars When we want to purchase Mild steel members from the market, the shopkeeper quotes the price of steel members in weight. When any type of steel members for use in house construction is required, we calculate the length of steel member in feet or meter but we are ignorant about the weight of steel.

Here are details of weight per meter for various types of steel members:This will help us for estimated weight and cost. It will also help at the time of purchase to avoid pilferage in weight. M S Steel round & square Bar

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Stainless Steel Reinforcing Bars

Introduction Deterioration of reinforced concrete caused by corrosion of the carbon steel reinforcing bars (rebars) is a worldwide problem. The corrosion product ("rust") occupies a greater volume than the original steel bar and this creates a pressure which causes cracking and subsequent spalling of the surrounding concrete.

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Corrosion of carbon steel rebars is greatly accelerated when chlorides are present in the concrete (along with the requisite moisture and oxygen levels to sustain the corrosion reactions). In some parts of the world, chlorides may be incorporated into the original mix due to their presence in the sand, aggregate or water. Most often, chlorides penetrate through the "cover" when the external surfaces of the concrete are exposed to seawater, marine atmospheres or de-icing salts. Several methods are currently employed in an attempt to reduce the corrosion of carbon steel rebars. These include: rebar coatings (fusion-bonded epoxy, galvanizing); increased concrete cover; reduced water/cement ratios; corrosion inhibitors added to the concrete mix, concrete sealers, cathodic protection; and concrete coatings or membranes. However, there is increasing interest in the use of reinforcing materials that have inherently good corrosion resistance, thus minimizing the need for maintenance and monitoring of the structure. Stainless steels are such materials and they have been used as concrete rebars in Europe, North America, Asia, Australia and Africa.

Advantages  

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Stainless steel reinforcing bars (rebar) and associated products are available to extend the lifetime of concrete structures in corrosive environments. Highway bridges, parking garages, coastal facilities and other structures have been built using stainless steel rebars. Some installations date back some 20 years ... one marine structure has a service history of 60 years ! In addition to improved corrosion resistance, austenitic stainless steel reinforcing can be supplied in the non-magnetic condition. This property is desirable in certain military, medical and scientific applications. Several grades of stainless steel combine favorable strength, ductility and toughness over a wide temperature range (including very low temperatures). These mechanical properties are advantageous for resistance to earthquakes. inherently good corrosion resistance. reduced life cycle cost for concrete structures. good strength. good weldability for common rebar grades. good ductility for common rebar grades (capable of 3d U-bends). no coatings to chip, crack or degrade. no coating damage to repair. no "exposed" cut ends to coat or cover. capable of withstanding shipping, handling, bending. magnetic or non-magnetic, depending on the alloy specified. good high- and low-temperature mechanical properties of common rebar grades. 13

Best One to Use Stainless Steel bars are very good for use, but Stainless Steel bars not used commonly, these type of bars used mostly in Megastructure and Highway bridges in Developed country like USA, Australia, South Africa, UK, U.A.E. and Qatar etc. Because Stainless Steel bars are very costly. Deformed steel bars are also best for using. Because  Affordable and Safe Construction in the 21st Century  Steely Protection Against Earthquake Damage  Enhancing the Safety of a Building  Stainless Steels

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Reference    

http://en.wikipedia.org/wiki/Rebar http://www.google.co.in ( For Searching) http://www.stainless-rebar.org/index.html http://www.corrosionsource.com/corrosioneering/journal/Jul02_Q iu/Jul02_Qiu_9.htm  http://www.cartech.com/techarticles.aspx?id=1576

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