Mar. 03, 2025
Guides
With competitive price and timely delivery, Xingtai Steel sincerely hope to be your supplier and partner.
Rebar is a shortened word form of reinforcing bar, which is a bar typically made of steel that is used to reinforce concrete and to improve its tensile strength. Concrete performs well under compression but is much weaker in tension. By adding reinforcement to concrete pours, the overall performance of concrete structures under loaded conditions is improved.
Rebar commonly has a deformation on the surface that is used to help concrete adhere to it. There are also plain rebar designs available that are used in applications such as highway pavement.
Steel rebar is marked to identify the size, the type of steel used, the yield strength which aligns with the grade of steel, and the point of origin or mill which produced the product. The steel types include carbon steel, low-alloy steel, stainless steel, rail steel, axle steel, and low-carbon chromium steel. The grade of steel may be designated as a numerical value or by a series of lines or dots that represent the grade.
The common types of rebar used in construction for the reinforcement of concrete include:
Tempered steel rebar
Basalt rebar
Epoxy coated rebar
Fiberglass rebar
Stainless steel rebar
Threaded rebar
Welded Wire Fabric (WWF)
The most commonly used variety of rebar is tempered steel rebar, also known as carbon steel rebar or black bar. It is inexpensive but corrodes more easily than other types of rebar.
Basalt rebar is a product formed from basalt, which is an inert volcanic rock, and which offers several advantages over standard steel rebar. Basalt rebar is 2-3 times stronger than steel rebar and is about ¼ the weight for a similar diameter product. In addition, basalt rebar is non-conductive electrically or thermally, is non-hygroscopic, and is resistant to corrosion.
Epoxy coated rebar, also known as green rebar, is commonly used in construction applications where there is an increased risk of exposure to corrosive elements. Applications include ones such as marine environments, bridges, or other locations where deicing salts may be applied. The epoxy coating is applied by the factory and is typically applied using an electrostatic spray in accordance with ASTM A775/A775M. The added coating increases the corrosion resistance anywhere from 70 to 1,700 times that of black steel rebar, however it is delicate and is subject to being damaged during shipping or installation, which reduces the effectiveness of the epoxy coating.
Fiberglass rebar, known also as fiberglass reinforced polymer rebar or Glass Fiber Reinforced Polymer (GFRP) rebar, makes use of a fiberglass resin wrapped with a fiberglass roving ' an interlaced series of glass fibers ' to form a reinforcement bar for construction. The primary advantage of fiberglass rebar is that it will never corrode from exposure to salts or other elements. In addition, fiberglass rebar possesses higher tensile strength than steel, affords significant weight reduction (75% lighter than steel) which saves on material handling and shipping costs, and has non-conductive electrical properties and thermal insulator properties when compared to steel rebar.
Use Thomas' Supplier Discovery Platform to find Suppliers of Fiberglass Rebar.
Stainless steel rebar substitutes stainless steel for carbon steel in use as a concrete reinforcement material for applications where high corrosion resistance is desired or for critical components of the structure. Corrosion of carbon steel typically results from a combination of carbonization of the concrete with chloride diffusion, where chlorides penetrate the concrete as a result of using deicing agents such as chloride-based salts, or from exposure to seawater splash. The reaction of the corrosive elements on the steel causes the formation of rust which expands in volume up to 6-7 times that of the original metal. This expansion process generates forces that can lead to cracking, spalling, and in some cases potential structural failure of the concrete.
The corrosion-resistant properties of stainless steel eliminate these mechanisms. Stainless steel is highly resistant to the effects of corrosion from the chloride penetration and is not dependent on the high alkalinity of concrete to afford protection to the steel. While there is a higher initial cost to its use, total life-cycle costs for the construction project over its service period may be reduced when the high costs of repair and maintenance are considered for the alternatives.
In the U.S., ASTM A955/A955M defines the requirements for the use of deformed and plain stainless steel bars for the reinforcement of concrete.
Use Thomas' Supplier Discovery Platform to find Suppliers of Stainless Steel Rebar.
Threaded rebar also referred to as jumbo rebar, contains single or double threaded ends on the bar to enable the use of standard UNC fasteners to be used for securing items in place, similar to an anchor bolt. Threads need to be cut by either first milling down the rebar to generate a turned-down section that is equal in diameter to the rebar deformation at its lowest point, and then utilizing a roll or cut thread process.
While not identified using the word rebar, welded wire fabric is a product constructed of fusion welded low carbon steel wire or stainless steel wire joined into a square grid pattern or mesh in common sizes that is used for the reinforcement of concrete slabs. It serves to enhance the tensile strength of concrete slabs in the same manner as other types of rebar.
Galvanized rebar adds a zinc coating to the steel rebar either with a hot or cold plating process or by use of electroplating, thus providing surface protection to help prevent rust and corrosion. European rebar makes use of an alloy principally containing the element manganese and is known for its low cost, however, they bend more easily and are not tolerant of applications that would expose the structure to severe weather such as tornados, hurricanes, and earthquakes.
This article presented a brief summary of a few of the common types of rebar used in construction to enhance the tensile strength of concrete. For information on additional topics, consult our other guides or visit the Thomas Supplier Discovery Platform to locate potential sources of supply or view details on specific products.
Sources:
Steel reinforcement
Two bundles of full-length rebar, which will be placed, bent, or cut as required by installation
Rebar (short for reinforcing bar), known when massed as reinforcing steel or reinforcement steel,[1] is a steel bar used as a tension device in reinforced concrete and reinforced masonry structures to strengthen and aid the concrete under tension. Concrete is strong under compression, but has low tensile strength. Rebar significantly increases the tensile strength of the structure. Rebar's surface features a continuous series of ribs, lugs or indentations to promote a better bond with the concrete and reduce the risk of slippage.
The most common type of rebar is carbon steel, typically consisting of hot-rolled round bars with deformation patterns embossed into its surface. Steel and concrete have similar coefficients of thermal expansion,[2] so a concrete structural member reinforced with steel will experience minimal differential stress as the temperature changes.
Other readily available types of rebar are manufactured of stainless steel, and composite bars made of glass fiber, carbon fiber, or basalt fiber. The carbon steel reinforcing bars may also be coated in zinc or an epoxy resin designed to resist the effects of corrosion, especially when used in saltwater environments. Bamboo has been shown to be a viable alternative to reinforcing steel in concrete construction.[3][4] These alternative types tend to be more expensive or may have lesser mechanical properties and are thus more often used in specialty construction where their physical characteristics fulfil a specific performance requirement that carbon steel does not provide.
History
[
edit
]
Reinforcing bars in masonry construction have been used since Antiquity, with Rome using iron or wooden rods in arch construction, later iron tie rods and anchor plates were employed across Medieval Europe, as a device to reinforce arches, vaults, and cupolas.[5][6] 2,500 meters of rebar was used in the 14th Century Château de Vincennes.[7]
During the 18th century, rebar was used to form the carcass of the Leaning Tower of Nevyansk in Russia, built on the orders of the industrialist Akinfiy Demidov. The cast iron[citation needed] used for the rebar was of high quality, and there is no corrosion on the bars to this day. The carcass of the tower was connected to its cast iron tented roof, crowned with one of the first known lightning rods.[8]
However, it was not until the mid-19th century that rebar displayed its greatest strengths with the embedding of steel bars into concrete, thus producing modern reinforced concrete. Several people in Europe and North America developed reinforced concrete in the s. These include Joseph-Louis Lambot of France, who built reinforced concrete boats in Paris () and Thaddeus Hyatt of the United States, who produced and tested reinforced concrete beams. Joseph Monier of France is one of the most notable figures for the invention and popularization of reinforced concrete. As a French gardener, Monier patented reinforced concrete flower pots in , before proceeding to build reinforced concrete water tanks and bridges.[9]
The Alvord Lake Bridge in San Francisco's Golden Gate Park, the first reinforced concrete bridge built in the United States
Ernest L. Ransome, an English engineer and architect who worked in the United States, made a significant contribution to the development of reinforcing bars in concrete construction. He invented twisted iron rebar, which he initially thought of while designing self-supporting sidewalks for the Masonic Hall in Stockton, California. His twisted rebar was, however, not initially appreciated and even ridiculed at the Technical Society of California, where members stated that the twisting would weaken the iron.[10] In , Ransome worked on the West Coast mainly designing bridges. One of these, the Alvord Lake Bridge in San Francisco's Golden Gate Park, was the first reinforced concrete bridge built in the United States. He used twisted rebar in this structure.[11]
At the same time Ransome was inventing twisted steel rebar, C.A.P. Turner was designing his "mushroom system" of reinforced concrete floor slabs with smooth round rods and Julius Kahn was experimenting with an innovative rolled diamond-shaped rebar with flat-plate flanges angled upwards at 45° (patented in ). Kahn predicted concrete beams with this reinforcing system would bend like a Warren truss, and also thought of this rebar as shear reinforcement. Kahn's reinforcing system was built in concrete beams, joists, and columns.
The system was both praised and criticized by Kahn's engineering contemporaries: Turner voiced strong objections to this system as it could cause catastrophic failure to concrete structures. He rejected the idea that Kahn's reinforcing system in concrete beams would act as a Warren truss and also noted that this system would not provide the adequate amount of shear stress reinforcement at the ends of the simply supported beams, the place where the shear stress is greatest. Furthermore, Turner warned that Kahn's system could result in a brittle failure as it did not have longitudinal reinforcement in the beams at the columns.
This type of failure manifested in the partial collapse of the Bixby Hotel in Long Beach, California and total collapse of the Eastman Kodak Building in Rochester, New York, both during construction in . It was, however, concluded that both failures were the consequences of poor quality labor. With the increase in demand of construction standardization, innovative reinforcing systems such as Kahn's were pushed to the side in favor of the concrete reinforcing systems seen today.[12]
Requirements for deformations on steel bar reinforcement were not standardized in US construction until about . Modern requirements for deformations were established in "Tentative Specifications for the Deformations of Deformed Steel Bars for Concrete Reinforcement", ASTM A305-47T. Subsequently, changes were made that increased rib height and reduced rib spacing for certain bar sizes, and the qualification of 'tentative' was removed when the updated standard ASTM A305-49 was issued in . The requirements for deformations found in current specifications for steel bar reinforcing, such as ASTM A615 and ASTM A706, among others, are the same as those specified in ASTM A305-49.[13]
Use in concrete and masonry
[
edit
]
Rebar has been placed atop a temporary wooden formwork deck prior to pouring concrete. The large horizontal rebar "cages" will be encased within a beam , while several thick vertical rebar stubs will stick out of the pour to form the base of a future column
Concrete is a material that is very strong in compression, but relatively weak in tension. To compensate for this imbalance in concrete's behavior, rebar is cast into it to carry the tensile loads. Most steel reinforcement is divided into primary and secondary reinforcement:
Primary reinforcement refers to the steel which is employed to guarantee the resistance needed by the structure as a whole to support the design loads.
Secondary reinforcement, also known as distribution or thermal reinforcement, is employed for durability and aesthetic reasons, by providing enough localized resistance to limit cracking and resist stresses caused by effects such as temperature changes and shrinkage.
Secondary applications include rebar embedded in masonry walls, which includes both bars placed horizontally in a mortar joint (every fourth or fifth course of block) or vertically (in the horizontal voids of cement blocks and cored bricks, which is then fixed in place with grout. Masonry structures held together with grout have similar properties to concrete - high compressive resistance but a limited ability to carry tensile loads. When rebar is added they are known as "reinforced masonry".
A similar approach (of embedding rebar vertically in designed voids in engineered blocks) is also used in dry-laid landscape walls, at least pinning the lowest course in place into the earth, also employed securing the lowest course and/or deadmen in walls made of engineered concrete or wooden landscape ties.
In unusual cases steel reinforcement may be embedded and partially exposed, as in the steel tie bars that constrain and reinforce the masonry Nevyansk Tower or ancient structures in Rome and the Vatican.
Physical characteristics
[
edit
]
Steel has a thermal expansion coefficient nearly equal to that of modern concrete. If this were not so, it would cause problems through additional longitudinal and perpendicular stresses at temperatures different from the temperature of the setting.[14] Although rebar has ribs that bind it mechanically to the concrete, it can still be pulled out of the concrete under high stresses, an occurrence that often accompanies a larger-scale collapse of the structure. To prevent such a failure, rebar is either deeply embedded into adjacent structural members (40'60 times the diameter), or bent and hooked at the ends to lock it around the concrete and other rebar. This first approach increases the friction locking the bar into place, while the second makes use of the high compressive strength of concrete.
Common rebar is made of unfinished tempered steel, making it susceptible to rusting. Normally the concrete cover is able to provide a pH value higher than 12 avoiding the corrosion reaction. Too little concrete cover can compromise this guard through carbonation from the surface, and salt penetration. Too much concrete cover can cause bigger crack widths which also compromises the local guard. As rust takes up greater volume than the steel from which it was formed, it causes severe internal pressure on the surrounding concrete, leading to cracking, spalling, and, ultimately, structural failure. This phenomenon is known as oxide jacking.
This is a particular problem where the concrete is exposed to salt water, as in bridges where salt is applied to roadways in winter, or in marine applications. Uncoated, corrosion-resistant low carbon/chromium (microcomposite), silicon bronze, epoxy-coated, galvanized, or stainless steel rebars may be employed in these situations at greater initial expense, but significantly lower expense over the service life of the project.[15][16]
Extra care is taken during the transport, fabrication, handling, installation, and concrete placement process when working with epoxy-coated rebar, because damage will reduce the long-term corrosion resistance of these bars.[17] Even damaged epoxy-coated bars have shown better performance than uncoated reinforcing bars, though issues from debonding of the epoxy coating from the bars and corrosion under the epoxy film have been reported.[18] These epoxy-coated bars are used in over 70,000 bridge decks in the US, but this technology was slowly being phased out in favor of stainless steel rebar as of because of its poor performance.[19][20]
Requirements for deformations are found in US-standard product specifications for steel bar reinforcing, such as ASTM A615 and ASTM A706, and dictate lug spacing and height.
Fibre-reinforced plastic rebar is also used in high-corrosion environments. It is available in many forms, such as spirals for reinforcing columns, common rods, and meshes. Most commercially available rebar is made from unidirectional fibers set in a thermoset polymer resin, and is often referred to as FRP.
Some special construction such as research and manufacturing facilities with very sensitive electronics may require the use of reinforcement that is non-conductive to electricity, and medical imaging equipment rooms may require non-magnetic properties to avoid interference. FRP rebar, notably glass fibre types have low electrical conductivity and are non-magnetic which is commonly used for such needs. Stainless steel rebar with low magnetic permeability is available and is sometimes used to avoid magnetic interference issues.
Reinforcing steel can also be displaced by impacts such as earthquakes, resulting in structural failure. The prime example of this is the collapse of the Cypress Street Viaduct in Oakland, California as a result of the Loma Prieta earthquake, causing 42 fatalities. The shaking of the earthquake caused rebars to burst from the concrete and buckle. Updated building designs, including more circumferential rebar, can address this type of failure.
Sizes and grades
[
edit
]
US sizes
[
edit
]
US/Imperial bar sizes give the diameter in units of 1'8 inch (3.2 mm) for bar sizes #2 through #8, so that #8 = 8'8 inch = 1-inch (25 mm) diameter.
There are no fractional bar sizes in this system. The "#" symbol indicates the number sign, and thus "#6" is read as "number six". The use of the "#" sign is customary for US sizes, however "No." is sometimes used instead. Within the trades rebar is known by a shorthand utilizing the bar diameter as descriptor, such as "four-bar" for bar that is four-eighths (or one-half) of an inch.
The cross-sectional area of a bar, as given by πr², works out to (bar size/9.027)², which is approximated as (bar size/9)² square inches. For example, the area of #8 bar is (8/9)² = 0.79 square inches.
Bar sizes larger than #8 follow the 1'8-inch rule imperfectly and skip sizes #12-13, and #15-17 due to historical convention. In early concrete construction bars 1 inch and larger were only available in square sections, and when large format deformed round bars became available around [21] the industry manufactured them to provide the cross-sectional area equivalent of standard square bar sizes that were formerly used. The diameter of the equivalent large format round shape is rounded to the nearest 1'8 inch to provide the bar size. For example, #9 bar has a cross section of 1.00 square inch (6.5 cm2), and therefore a diameter of 1.128 inches (28.7 mm). #10, #11, #14, and #18 sizes correspond to 11'8 inch, 11'4, 11'2, and 2 inch square bars, respectively.[22]
Sizes smaller than #3 are no longer recognized as standard sizes. These are most commonly manufactured as plain round undeformed rod steel, but can be made with deformations. Sizes smaller than #3 are typically referred to as "wire" products and not "bar", and specified by either their nominal diameter or wire gage number. #2 bars are often informally called "pencil rod" as they are about the same size as a pencil.
When US/Imperial sized rebar are used in projects with metric units, the equivalent metric size is typically specified as the nominal diameter rounded to the nearest millimeter. These are not considered standard metric sizes, and thus is often referred to as a soft conversion or the "soft metric" size. The US/Imperial bar size system recognizes the use of true metric bar sizes (No. 10, 12, 16, 20, 25, 28, 32, 36, 40, 50 and 60 specifically) which indicates the nominal bar diameter in millimeters, as an "alternate size" specification. Substituting a true metric size for a US/Imperial size is called a hard conversion, and sometimes results in the use of a physically different sized bar.
Steel reinforcement bars with color codes indicating the grade
US rebar size chart Imperial
bar size
Metric bar
size (soft)
Linear Mass Density Nominal diameter Nominal area
lb
'
ft
kg
'
m
(in) (mm) (in²) (mm²) #2[a] No.6 0.167 0.249 0.250 =
2
'
8
=
1
'
4
6.35 0.05 32 #3 No.10 0.376 0.560 0.375 =
3
'
8
9.53 0.11 71 #4 No.13 0.668 0.994 0.500 =
4
'
8
=
1
'
2
12.7 0.20 129 #5 No.16 1.043 1.552 0.625 =
5
'
8
15.9 0.31 200 #6 No.19 1.502 2.235 0.750 =
6
'
8
=
3
'
4
19.1 0.44 284 #7 No.22 2.044 3.042 0.875 =
7
'
8
22.2 0.60 387 #8 No.25 2.670 3.973 1.000 =
8
'
8
25.4 0.79 510 #9 No.29 3.400 5.060 1.128 '
9
'
8
28.7 1.00 645 #10 No.32 4.303 6.404 1.270 '
10
'
8
32.3 1.27 819 #11 No.36 5.313 7.907 1.410 '
11
'
8
35.8 1.56 1,006 #14 No.43 7.650 11.384 1.693 '
14
'
8
43.0 2.25 1,452 #18 No.57 13.60 20.239 2.257 '
18
'
8
57.3 4.00 2,581^Historic size designation that is no longer in common use.[
citation needed
]
Canadian sizes
[
edit
]
Metric bar designations represent the nominal bar diameter in millimeters, rounded to the nearest 5 mm.
Metric
bar size
Linear Mass Density
(kg/m)
Nominal diameter
(mm)
Cross-sectional
Area (mm²)
10M 0.785 11.3 100 15M 1.570 16.0 200 20M 2.355 19.5 300 25M 3.925 25.2 500 30M 5.495 29.9 700 35M 7.850 35.7 45M 11.775 43.7 55M 19.625 56.4
European sizes
[
edit
]
Metric bar designations represent the nominal bar diameter in millimetres. Preferred bar sizes in Europe are specified to comply with Table 6 of the standard EN ,[23] although various national standards still remain in force (e.g. BS in the United Kingdom). In Switzerland some sizes are different from European standard.
Steel reinforcement in storage
Metric
bar size
Linear mass
density (kg/m)
Nominal
diameter (mm)
Cross-sectional
area (mm²)
6,0 0.222 6 28.3 8,0 0.395 8 50.3 10,0 0.617 10 78.5 12,0 0.888 12 113 14,0 1.21 14 154 16,0 1.58 16 201 20,0 2.47 20 314 25,0 3.85 25 491 28,0 4.83 28 616 32,0 6.31 32 804 40,0 9.86 40 50,0 15.4 50
Australian sizes
[
edit
]
Reinforcement for use in concrete construction is subject to the requirements of Australian Standards AS (Concrete Structures) and AS/NZS (Steel Reinforcing for Concrete). There are other standards that apply to testing, welding and galvanizing.
The designation of reinforcement is defined in AS/NZS using the following formats:
Reinforcement steel bar Grade 500 Class N Nominal Diameter (mm) Cross-sectional area (mm sq) Mass per metre length, kg/m 12 113 0.888 16 201 1.58 20 314 2.47 24 452 3.55 28 616 4.83 32 804 6.31 36 7.99
Shape/ Section
D- deformed ribbed bar, R- round / plain bar, I- deformed indented bar
Ductility Class
L- low ductility, N- normal ductility, E- seismic (Earthquake) ductility
Standard grades (MPa)
250N, 300E, 500L, 500N, 500E
Examples:
For more information, please visit a706 rebar.
D500N12 is deformed bar, 500 MPa strength, normal ductility and 12 mm nominal diameter - also known as "N12"
Bars are typically abbreviated to simply 'N' (hot-rolled deformed bar), 'R' (hot-rolled round bar), 'RW' (cold-drawn ribbed wire) or 'W' (cold-drawn round wire), as the yield strength and ductility class can be implied from the shape. For example, all commercially available wire has a yield strength of 500 MPa and low ductility, while round bars are 250 MPa and normal ductility.
New Zealand
[
edit
]
Reinforcement for use in concrete construction is subject to the requirements of AS/NZS (Steel Reinforcing for Concrete). There are other standards that apply to testing, welding and galvanizing.
'Reinforcement steel bar Grade 300 & 500 Class E
Nominal Diameter (mm) Cross-sectional area (mm sq) Mass per metre length, kg/m 6 28.3 0.222 10 78.5 0.617 12 113 0.888 16 201 1.58 20 314 2.47 25 491 3.85 32 804 6.31 40 9.86
India
[
edit
]
Rebars are available in the following grades as per IS:- FE 415/FE 415D/FE 415S/FE 500/FE 500D/FE 500S/FE 550, FE550D, FE 600. Rebars are quenched with water at a high level pressure so that the outer surface is hardened while the inner core remains soft. Rebars are ribbed so that the concrete can have a better grip. Coastal regions use galvanized rebars to prolong their life. BIS rebar sizes are 10, 12, 16, 20, 25, 28, 32, 36, 40 and 50 millimeters.
Jumbo and threaded bar sizes
[
edit
]
Very large format rebar sizes are widely available and produced by specialty manufacturers. The tower and sign industries commonly use "jumbo" bars as anchor rods for large structures which are fabricated from slightly oversized blanks such that threads can be cut at the ends to accept standard anchor nuts.[24][25] Fully threaded rebar is also produced with very coarse threads which satisfy rebar deformation standards and allow for custom nuts and couplers to be used.[26] Note that these customary sizes while in common use, do not have consensus standards associated with them, and actual properties may vary by manufacturer.
Jumbo rebar size chart Imperial
bar size
Metric bar
size (soft)
Linear Mass Density Nominal diameter
(outside of threaded zone)
Nominal area
(outside of threaded zone)
lb
'
ft
(kg/m) (in) (mm) (in²) (mm²) #14J - 9.48 14.14 1.88 47.8 2.78 #18J - 14.60 21.78 2.34 59.4 4.29 Threaded rebar size chart Imperial
bar size
Metric bar
size (soft)
Linear Mass Density Maximum diameter Nominal area
lb
'
ft
(kg/m) (in) (mm) (in²) (mm²) (#18 and smaller are the same as US/Imperial sizes) #20 No.63 16.70 24.85 2.72 69 4.91 #24 No.75 24.09 35.85 3.18 81 7.06 #28 No.90 32.79 48.80 3.68 94 9.62 1" No.26 3.01 4.48 1.25 32 0.85 548 1
1
'
4
" No.32 4.39 6.53 1.45 37 1.25 806 1
3
'
8
" No.36 5.56 8.27 1.63 41 1.58 1
3
'
4
" No.46 9.23 13.73 2.01 51 2.58 2
1
'
2
" No.65 18.20 27.08 2.80 71 5.16 3" No.75 24.09 35.85 3.15 80 6.85
Grades
[
edit
]
Rebar is available in grades and specifications that vary in yield strength, ultimate tensile strength, chemical composition, and percentage of elongation.
The use of a grade by itself only indicates the minimum permissible yield strength, and it must be used in the context of a material specification in order to fully describe product requirements for rebar. Material specifications set the requirements for grades as well as additional properties such as, chemical composition, minimum elongation, physical tolerances, etc. Fabricated rebar must exceed the grade's minimum yield strength and any other material specification requirements when inspected and tested.
In US use, the grade designation is equal to the minimum yield strength of the bar in ksi ( psi) for example grade 60 rebar has a minimum yield strength of 60 ksi. Rebar is most commonly manufactured in grades 40, 60, and 75 with higher strength readily available in grades 80, 100, 120 and 150. Grade 60 (420 MPa) is the most widely used rebar grade in modern US construction. Historic grades include 30, 33, 35, 36, 50 and 55 which are not in common use today.
Some grades are only manufactured for specific bar sizes, for example under ASTM A615, Grade 40 (280 MPa) is only furnished for US bar sizes #3 through #6 (soft metric No.10 through 19). Sometimes limitations on available material grades for specific bar sizes is related to the manufacturing process used, as well as the availability of controlled quality raw materials used.
Some material specifications cover multiple grades, and in such cases it is necessary to indicate both the material specification and grade. Rebar grades are customarily noted on engineering documents, even when there are no other grade options within the material specification, in order to eliminate confusion and avoid potential quality issues such as might occur if a material substitution is made. Note that "Gr." is the common engineering abbreviation for "grade", with variations on letter capitalization and the use of a period.[27]
In certain cases, such as earthquake engineering and blast resistant design where post-yield behavior is expected, it is important to be able to predict and control properties such as the maximum yield strength and minimum ratio of tensile strength to yield strength. ASTM A706 Gr. 60 is an example of a controlled property range material specification which has a minimum yield strength of 60 ksi (420 MPa), maximum yield strength of 78 ksi (540 MPa), minimum tensile strength of 80 ksi (550 MPa) and not less than 1.25 times the actual yield strength, and minimum elongation requirements that vary by bar size.
In countries that use the metric system, the grade designation is typically the yield strength in megapascals MPa, for example grade 400 (similar to US grade 60, however metric grade 420 is actually the exact substitution for the US grade).
Common US specifications, published by ACI and ASTM, are:
American Concrete Institute: "ACI 318-14 Building Code Requirements for Structural Concrete and Commentary", ISBN 978-0--930-3 ()
ASTM A82: Specification for Plain Steel Wire for Concrete Reinforcement
ASTM A184/A184M: Specification for Fabricated Deformed Steel Bar Mats for Concrete Reinforcement
ASTM A185: Specification for Welded Plain Steel Wire Fabric for Concrete Reinforcement
ASTM A496: Specification for Deformed Steel Wire for Concrete Reinforcement
ASTM A497: Specification for Welded Deformed Steel Wire Fabric for Concrete Reinforcement
ASTM A615/A615M: Deformed and plain carbon-steel bars for concrete reinforcement
ASTM A616/A616M: Specification for Rail-Steel Deformed and Plain Bars for Concrete Reinforcement
ASTM A617/A617M: Specification for Axle-Steel Deformed and Plain Bars for Concrete Reinforcement
ASTM A706/A706M: Low-alloy steel deformed and plain bars for concrete reinforcement
ASTM A722/A722M: Standard Specification for High-Strength Steel Bars for Prestressed Concrete
ASTM A767/A767M: Specification for Zinc-Coated (Galvanized) Steel Bars for Concrete Reinforcement
ASTM A775/A775M: Specification for Epoxy-Coated Reinforcing Steel Bars
ASTM A934/A934M: Specification for Epoxy-Coated Prefabricated Steel Reinforcing Bars
ASTM A955: Deformed and plain stainless-steel bars for concrete reinforcement (Supplementary Requirement S1 is used when specifying magnetic permeability testing)
ASTM A996: Rail-steel and axle-steel deformed bars for concrete reinforcement
ASTM A: Standard Specification for Deformed and Plain, Low-carbon, Chromium, Steel Bars for Concrete Reinforcement
ASTM marking designations are:
Historically in Europe, rebar is composed of mild steel material with a yield strength of approximately 250 MPa (36 ksi). Modern rebar is composed of high-yield steel, with a yield strength more typically 500 MPa (72.5 ksi). Rebar can be supplied with various grades of ductility. The more ductile steel is capable of absorbing considerably more energy when deformed - a behavior that resists earthquake forces and is used in design. These high yield strength ductile steels are usually produced using the TEMPCORE process,[28] a method of thermomechanical processing. The manufacture of reinforcing steel by re-rolling finished products (e.g. sheets or rails) is not allowed.[29] In contrast to structural steel, rebar steel grades are not harmonized yet across Europe, each country having their own national standards. However some standardization of specification and testing methods exist under EN and EN ISO :
BS EN : Steel for the reinforcement of concrete. Weldable reinforcing steel. General. ()
BS : Steel for the reinforcement of concrete. Weldable reinforcing steel. Bar, coil and decoiled product. Specification. (/)
BS : Steel wire for the reinforcement of concrete products. Specification ()
BS : Steel fabric for the reinforcement of concrete. Specification ()
BS : Stainless steel bars for the reinforcement of and use in concrete. Requirements and test methods. (/)
DIN 488-1: Reinforcing steels - Part 1: Grades, properties, marking ()
DIN 488-2: Reinforcing steels - Part 2: Reinforcing steel bars ()
DIN 488-3: Reinforcing steels - Part 3: Reinforcing steel in coils, steel wire ()
DIN 488-4: Reinforcing steels - Part 4: Welded fabric ()
DIN 488-5: Reinforcing steels - Part 5: Lattice girders ()
DIN 488-6: Reinforcing steel - Part 6: Assessment of conformity ()
BS EN ISO -1: Steel for the reinforcement and prestressing of concrete. Test methods. Reinforcing bars, wire rod and wire. ()
BS EN ISO -2: Steel for the reinforcement and prestressing of concrete. Test methods. Welded fabric. ()
Placing rebar
[
edit
]
Steel wire used to secure rebar before it is set in concrete. A centimeter rule is provided for reference.
Rebar cages are fabricated either on or off the project site commonly with the help of hydraulic benders and shears. However, for small or custom work a tool known as a Hickey, or hand rebar bender, is sufficient. The rebars are placed by steel fixers ("rodbusters" or concrete reinforcing iron workers), with bar supports and concrete or plastic rebar spacers separating the rebar from the concrete formwork to establish concrete cover and ensure that proper embedment is achieved. The rebars in the cages are connected by spot welding, tying steel wire, sometimes using an electric rebar tier, or with mechanical connections. For tying epoxy-coated or galvanized rebars, epoxy-coated or galvanized wire is normally used, respectively.
Stirrups
[
edit
]
Stirrup sample
Stirrups form the outer part of a rebar cage. Stirrups are usually rectangular in beams, and circular in piers and are placed at regular intervals along a column or beam to secure the structural rebar and prevent it from shifting out of position during concrete placement. The main usage for stirrups or ties is to increase the shear capacity of reinforced concrete component it is included in.[30]
Welding
[
edit
]
The American Welding Society (AWS) D 1.4 sets out the practices for welding rebar in the US Without special consideration the only rebar that is ready to weld is W grade (Low-alloy ' A706). Rebar that is not produced to the ASTM A706 specification is generally not suitable for welding without calculating the "carbon-equivalent". Material with a carbon-equivalent of less than 0.55 can be welded.
ASTM A 616 & ASTM A 617 (now replaced by the combined standard A996) reinforcing bars are re-rolled rail steel and re-rolled rail axle steel with uncontrolled chemistry, phosphorus and carbon content. These materials are not common.
Rebar cages are normally tied together with wire, although spot welding of cages has been the norm in Europe for many years, and is becoming more common in the United States. High strength steels for prestressed concrete cannot be welded.[citation needed]
Reinforcement placement in rolls
[
edit
]
Roll reinforcement system is a remarkably fast and cost-efficient method for placing a large quantity of reinforcement over a short period of time. Roll reinforcement is usually prepared off-site and easily unrolled on site. Roll reinforcement placement has been applied successfully in slabs (decks, foundations), wind energy mast foundations, walls, ramps, etc.
Mechanical connections
[
edit
]
Also known as "mechanical couplers" or "mechanical splices", mechanical connections are used to connect reinforcing bars together. Mechanical couplers are an effective means to reduce rebar congestion in highly reinforced areas for cast-in-place concrete construction. These couplers are also used in precast concrete construction at the joints between members.
The structural performance criteria for mechanical connections varies between countries, codes, and industries. As a minimum requirement, codes typically specify that the rebar to splice connection meets or exceeds 125% of the specified yield strength of the rebar. More stringent criteria also requires the development of the specified ultimate strength of the rebar. As an example, ACI 318 specifies either Type 1 (125% Fy) or Type 2 (125% Fy and 100% Fu) performance criteria.[31]
For concrete structures designed with ductility in mind, it is recommended that the mechanical connections are also capable of failing in a ductile manner, typically known in the reinforcing steel industry as achieving "bar-break". As an example, Caltrans specifies a required mode of failure (i.e., "necking of the bar").[32]
Safety
[
edit
]
Rebars with temporary plastic safety caps installed
To prevent injury, the protruding ends of steel rebar are often bent over or covered with special steel-reinforced plastic caps.[33]
Designations
[
edit
]
Reinforcement is usually tabulated in a "reinforcement schedule" on construction drawings. This eliminates ambiguity in the notations used around the world. The following list provides examples of the notations used in the architectural, engineering, and construction industry.
New Zealand Designation Explanation HD-16-300, T&B, EW High strength (500 MPa) 16 mm diameter rebars spaced at 300 mm centers (center-to-center distance) on both the top and bottom face and in each way as well (i.e., longitudinal and transverse). 3-D12 Three mild strength (300 MPa) 12 mm diameter rebars R8 Stirrups @ 225 MAX D grade (300 MPa) smooth bar stirrups, spaced at 225 mm centres. By default in New Zealand practice all stirrups are normally interpreted as being full, closed, loops. This is a detailing requirement for concrete ductility in seismic zones; If a single strand of stirrup with a hook at each end was required, this would typically be both specified and illustrated. United States Designation Explanation #4 @ 12 OC, T&B, EW Number 4 rebars spaced 12 inches on center (center-to-center distance) on both the top and bottom faces and in each way as well, i.e. longitudinal and transverse. (3) #4 Three number 4 rebars (usually used when the rebar perpendicular to the detail) #3 ties @ 9 OC, (2) per set Number 3 rebars used as stirrups, spaced at 9 inches on center. Each set consists of two ties, which is usually illustrated. #7 @ 12" EW, EF Number 7 rebar spaced 12 inches apart, placed in each direction (each way) and on each face.
Reuse and recycling
[
edit
]
Workers extracting rebar from demolition rubble in China
Rebar is frequently recycled, and rebar is often made entirely from recycled steel.[34] Nucor, the largest steel producer in the United States, claims its steel bar products are made from 97% recycled steel.[35]
References
[
edit
]
Dr. N. Subramanian, Ph.D., FNAE
Headed bars: An alternative to hooked bars
Headed bars may provide a desirable alternative to hooked bars from the consideration of design as well as constructability. They are available with rectangular, round, or elliptical heads and the heads may be formed by friction welding of plates, forging an upset bearing surface at the end of a reinforcing bar, or forging threads into the end of the bar, which are then used to attach the plate.
The use of headed bars instead of hooked bars offer several advantages like requirement of reduced development length, reduced congestion, ease of transport and fixing at site, better concrete consolidation, and better performance under seismic loads. The heads of 4Ab size provides anchorage through a combination of bond and bearing, whereas the heads of 9Ab size provides anchorage only through bearing. ACI 318-19 provided an equation to determine the development length of headed bars. Headed bars can be used advantageously in a variety of applications, including beam-column joints, knee joints, pile caps, column-roof slab connections, anchor cantilever beams, dapped end beams, corbels, transverse shear reinforcements, and shear wall cross ties.
Introduction
Historically bonded straight or hooked rebars were used to provide rebar anchorage. This method of anchoring reinforcement in concrete assumes sufficient bond between the rebar and the concrete. However, straight or hooked rebar may not provide the most effective anchorage and there are a few situations where headed bars may provide a desirable solution. When such headed bars are used, the required anchorage is achieved through bearing on the head or a combination of rebar bond and bearing on rebar deformations (see Fig.1)
Figure 1: Anchorage achieved through bearing on head and a combination of rebar bond and bearing on rebar deformations (Source: Thompson et al., )
Figure 1: Anchorage achieved through bearing on head and a combination of rebar bond and bearing on rebar deformations (Source: Thompson et al., )
The use of hooks often results in steel congestion, difficult fabrication and construction, and greater potential for poor concrete placement. In addition, cyclic loading tends to degrade the anchorage capacity due to the slip. The use of anchor plates or heads either welded or threaded to the longitudinal bar (often called headed bars) has been identified as a viable alternative to hooked bars in a variety of applications such as beam-column joints, knee joints, pile caps, column-roof slab connections, anchor cantilever beams, dapped end beams, corbels, transverse shear reinforcements, and shear wall cross ties. They also provide a number of advantages like ease of fabrication, construction, and concrete placement.
History of Headed Bars
Headed reinforcing bars have evolved from headed stud anchors. Studies on stud anchors began during 's by the Nelson Stud Welding Company at Lehigh University (McMackin et al., ). Subsequently shear studs were found to be useful as punching shear reinforcement in flat slabs, based on the work by Dilger and Ghali at the University of Calgary, Canada (Dilger and Ghali, and Mokhtar et al., ). They found that closed stirrups are structurally deficient as punching shear reinforcement and difficult to construct, and hence suggested double-headed shear studs as an alternate solution. They recommended a head size of 10 times the bar area is necessary for proper anchorage of the studs. Based on these recommendations, the company Decon patented and commercially produced stud-rails with larger head areas in .
Caltrans in USA also performed a study of headed reinforcement in the 's, in order to anchor large diameter bars connecting bridge piers and box-girder superstructures (Stoker et al., ). The Alaska Oil and Gas Association (AOGA) was interested in the 's to use double-headed bars as shear reinforcement in heavily reinforced concrete offshore oil platforms, who conducted several series of tests. Although the results of these tests are proprietary, some of them have been reported by Berner et al. ().
A friction-welded headed bar was developed, based on the work performed by Norwegian Contractors, Metalock and SINTEF (Thompson et al., ). This bar design has already been used extensively in several offshore and coastal structures. Some of them include: Oseburg Platform A, Gullfaks Platform C, the Ekofisk Barrier Wall, and Sleipner Platform A (both the original and revised designs), all of which are located in the North Sea (Berner and Hoff, ). Metalock patented the friction-welding technology and produced and started to sell friction-welded headed bars in the USA, under the banner of Headed Reinforcement Corporation (HRC).
At the same time, ERICO developed a threaded headed bar and marketed it in Europe during the 's (Thompson et al., ). In the 's, after its use in the offshore industry was successful, ERICO began to sell this product in the US market, under the trademark Lenton Terminator. Their headed bars had a smaller head than the products of HRC and Decon, with heads having only 4 times the bar area rather than 10 (Thompson et al., ). ERICO and HRC now support headed bar research focused primarily on bridge and seismic related applications. An extensive research was sponsored by HRC at the University of Texas at Austin and conducted by three Ph.D. students: DeVries, Bashandy, and Thompson (Bashandy, , DeVries, , DeVries, et al.,, and Thompson, ). They explored many of the potential applications and proposed anchorage provisions, and some of these provisions have been included in the ACI 318 Building Code (Thompson et al., ). Marchetto (), Alrasyid, et al. (), Lequesne (), and Wright and McCabe () provide more literature review on headed bars.
Manufacturers and Standards of Headed bars
As mentioned earlier, HRC and ERICO are the first manufacturers of the headed bar. HRC produced friction-welded heads and provided four types of heads: square, rectangular, circular, and oval. ERICO produced a tapered thread connection between the reinforcing bar and the head, which when screwed provided a headed bar. Other firms such as Dextra Group, Bar Splice, and Dayton are also manufacturing similar types of headed bars.
Many headed deformed bar manufacturers offer products made from a variety of stainless steel alloys also. Headed deformed bars are also offered in epoxy and galvanic coatings. These coatings typically conform to the same coating standards as the reinforcing bar coatings (ASTM A775, A934, and A767).
Figure 2: Obstruction limits for Class HA heads, as per ASTM A970 (Source: CRSI, )
Figure 2: Obstruction limits for Class HA heads, as per ASTM A970 (Source: CRSI, )
Class HA heads must have a net bearing area of at least 4 times the area of the bar, Ab (Abrg ' 4Ab). The net bearing area will be the area of the head minus area of the bar (Abrg = Ahead - Ab). The bearing area has to be a single, nominally flat surface perpendicular to the longitudinal axis of the bar.
Class HA heads must not have obstructions in the deformation pattern in front of the head greater than 2db, (where db is the nominal diameter of bar) along the axis of the bar. The obstructions must not have a diameter greater than 1.5db, as shown in Fig 2.
Class HA heads must develop the minimum specified tensile strength of the bar.
Class HA heads must be marked with a letter 'H' to indicate it was produced in conformance with Annex A1 of ASTM A970.
It has to be noted that all the headed bars available in the market do not meet the Class HA requirements of ASTM A970.
Headed bars with rectangular, round, or elliptical heads are available. The heads may be welded, forged, or threaded (Fig. 3).
Welded Heads: In this type, the head is welded to the reinforcing bar either through stick welding or friction welding. For head attachment method, A970 limits its use to ASTM A706 reinforcement.
Forged Heads: In this type, the head is produced by integrally hot-forging the head from the bar itself. For this method of head attachment, A970 permits either ASTM A706 or A615 reinforcing bars.
Threaded Heads: In this type, the head is attached to the rebar using taper or straight threads (internal to the head) or by a separate internally threaded nut and counter nut (see Fig.3(c)). For threaded heads, A970 permits either ASTM A615 or A706 reinforcing bars to be used.
Figure 3: Types of heads: (a) Friction welded head, (b) Forged head, (c) Threaded head, (d) Various types of headed bars with a standard hook (25 mm diameter) (Source: Thompson et al., )
Figure 3: Types of heads: (a) Friction welded head, (b) Forged head, (c) Threaded head, (d) Various types of headed bars with a standard hook (25 mm diameter) (Source: Thompson et al., )
Advantages of Using Headed Bars
The advantages of using headed bars are particularly evident when used in heavily reinforced concrete sections, where rebar congestion results in constructability problems. Hence, they are being used increasingly in civil infrastructure projects, nuclear power plants, and multi-storey buildings, where reinforcement congestion normally occurs.
The advantages of headed bars over reinforcing bars with a standard hook are:
The use of headed bars eliminates the requirement of bending the bars for satisfying anchorage length and also allows the reduction in tension development length.
The use of headed bars results in reduced congestion, ease of placement, and better concrete consolidation. Such reduction of congestion will also result in better behavior under seismic loads.
It is easier to insert the longitudinal bar in a cage during construction. Longitudinal bars with a hook protruding at one or both ends can make insertion of the hooked bar into a reinforcing bar cage difficult, especially if there are bars transverse to the hooked bar.
Since headed bars do not protrude as much as hooks there is less impact on cover constraints.
The transportation of straight lengths of rebars with headed ends is easier than transporting rebars with bent anchorages.
The on-site handling and fixing also become easier. Thus, the use of headed bars can offer considerable time and cost advantages as well as potential improvement in the quality of concrete. The head can be screwed or unscrewed to suit any adjustment if needed.
Types of Headed Bars
Most manufacturers of headed bars produce products with two sizes -4Ab and 9Ab- of heads (Goodman, ). The smaller 4Ab head will have a net bearing area of at least four times the cross-sectional area of rebars, complying with ACI 318-19 and ASTM A970 requirements (The net bearing area equals the area of the head minus the nominal area of the bar (Abrg = Ahead ' Ab). In this case, the anchorage is provided through a combination of bond (development length) and bearing. This small size head is used to terminate reinforcing bars in lieu of a standard hook (replacing standard hooks), which will improve constructability and reduce congestion. In most cases, the installation parameters for the headed bar are the same as that of the hooked bar they are replacing. It has to be noted that ACI 318-19 code does allow for a shorter development length when using headed bars.
The larger 9Ab heads will have a net bearing area of nine times the cross-sectional area of rebars (this was the standard in the USA prior to and the standard head in Europe and Canada now. It has a gross bearing area (including the area of bar > 10 Ab). Caltrans in the USA approved the use of full-size (9Ab) headed bars for bridges. It is important to note that the 9Ab head is bond-independent (no development length required). The anchorage in this case is provided through bearing alone directly beneath the head. The 9Ab heads are used to terminate reinforcing bars when the point of maximum stress is close to the end of the bar or when the development length leading up to the head is neglected during design.
As mentioned already, headed bar reinforcement is usually formed by friction welding of plates, by forging an upset bearing surface at the end of a reinforcing bar, or by forging threads into the end of the bar, which are then used to attach the plate. Headed bar reinforcement must comply with ASTM A970/A970M-18 requirements, which include tensile tests that confirm that necking occurs at least one diameter away from the head. Headed bar reinforcement must be made of A706-Grade 60 steel and meets the stress and strain requirements of Caltrans Seismic Design Criteria (SDC).
The Behavior of Headed Bars
Thompson et al. () suggested that the headed bar anchorage is provided by a combination of head bearing and bond. The initial anchorage is provided by the bond between the concrete and rebar. As additional load is applied to the bar, the bond achieves peak capacity and begins to decline. As the process of bond deterioration occurs, the bond anchorage is transferred to the head, causing a rise in the head bearing. The anchorage capacity at failure is provided by a combination of peak head bearing and reduced bond. Thompson et al. () opinioned that strut-and-tie models are the best for determining the anchorage length and that the node and strut dimensions play a critical role in defining the anchorage length. They also recommended a minimum anchorage length of 6db.
Tests conducted by Chun et al. () and Kang et al. () reveal that the hysteretic behaviour of exterior joints constructed with headed bars was similar to or even superior to joints with hooked bars. Head size with a net area of four times the bar area was sufficient to anchor the beam reinforcement effectively (with a development length shorter than that needed for hooked bars) within the exterior beam-column joint. For roof-level connections, anchoring the column heads above the beam bars and adding an additional layer of transverse reinforcement led to improved behavior.
Development Length of Headed Bars
As per ACI 318-19, the headed bar should comply with the provisions of ASTM A970. However, in Europe, the ISO is followed. In India, IS 456, IRC 112 as well as the design guide SP 34 allow the use of headed bars. It has to be noted that the IRC 112 provisions are similar to the Eurocode 2 provisions. Though the IS 456: states that mechanical devices can be used to anchor bars with the approval of the engineer-in-charge, it does not contain any clause to calculate the anchorage length. Clause 25.4.4.2 of the ACI 318-19 code suggests Eqn. 1 to determine the development length of headed deformed bars in tension, Ldt (see Fig. 4).
Where, Ldt = development length in tension of headed deformed bar, measured from the critical section to the bearing (inside) face of the head, (mm), 'e, 'p, 'o, and 'c are factors used to modify development length based on reinforcement coating, parallel tie reinforcement, side cover and confinement, and concrete strength, respectively ( 'e = 1.2 for epoxy-coated bars = 1.0 for uncoated or zinc-coated bars- values of other modification factors are given in Table 25.4.4.3 of ACI 318-19), fy = specified yield strength of the reinforcing bar (MPa), fc' = specified compressive cylinder strength of concrete (MPa) ' 40 MPa, and db = nominal diameter of the bar (mm). Note that Eqn. 1 results in a development length of approximately 80% of that required for hooked bars. Also Eqn. 1 is not a function of the head size, though it is indirectly accounted for the minimum requirements.
Figure 4: Development length of headed deformed bars (Source: CRSI, )
Figure 4: Development length of headed deformed bars (Source: CRSI, )
ACI 318-19 required that the headed bar should satisfy the following: (1) The yielding strength of bar should not exceed 420 MPa; (2) The maximum bar diameter should be ' 36mm; (3) The net bearing area should be at least 4Ab, where Ab is the area of bar; (4) Clear cover of the bar should not be less than 2db, (5) Clear spacing between bars should not be less than 4db, and (6) Normal weight concrete is used. The above restrictions are based on the available experimental results (Thompson et al., , Shao, et al., ). CRSI () suggests that when measuring cover, the measurement is taken from the edge of concrete to the bar, not to the head. However, it is better to take the cover from the edge of concrete to the head. Similarly, as per CRSI (), the spacing is measured from the inner edge of each bar, and not to the reinforcing bar centerline or the head.
In a recen
Construction of house needs different materials and hence needs study. The general guide points have been discussed by us in Material Buying Guide In General. Here we discuss buying guide for steel.
One need to do adequate research when you plan to buy steel bars. The steel bars are important for the life of the structural system. They are known as rebars in short form. They are also known as reinforcing bar or reinforcement steel.
Steel bars and cement are the most important materials used in the building. The strength of building is directly related to the strength of steel bars. We already discussed the cement buying guide in our recent content.
There are two types of steel bars in the market.
Mild steel bars are plain in surface and are round sections of diameter from 6 to 50 mm. They can be manufactured in long length and can be cut quickly and bend easily without damage.
Mild steel bars are available in Fe410-S (Grade 60) or Fe410-O (Grade 40).
Medium tensile steel bars are available in Fe540 (Grade 75)
High strength deformed steel bars are provided with lugs, ribs or deformation on the surface of the bar to improve the bond with the concrete. They are also twisted to improve the bond with the concrete.
Cold twisted deformed bars (Ribbed or Tor Steel Bars) are recommended as best quality steel bars for construction work.
They are available in Grade Fe415, Fe415D, Fe500, Fe500D, Fe550, Fe550D, and Fe600.
Fe indicates the specified 0.2 percent proof stress or yield stress in Newton per square millimeter.
You will have to spend a lot of time towards reviewing types, brands and its grade while buying.
Steel bars are needed as reinforcement in RCC structure. Concrete is the materials that is very weak in tension but strong in compression. To compensate for this imbalance of concrete, we provide steel bars in concrete to increase its tensile strength.
You therefore have to select the right type and grade of steel bars depending on your requirement or as considered in structural design/structural drawing by the structural engineer.
First you have to decide why and where do you need steel? i.e. for foundation, slab, and beam, column or for water tank and where is your area located? I.e. near the sea shore is It in corrosion prone area? You may than need CRS steel.
You can check the quality of steel bars by following steps
Check the percentage of deviation (Rolling Margin) in weight of reinforcement steel.
Rolling margin is very important when you buy in tonnes, and you get paid in lengths.
Avoid using steel from those rolling mills which use 'rerolled or scrap steel' as a row material. These are likely to have higher carbon content, which are prone to high corrosion.
b) Always ask for 'chemical composition' test from the supplier. Apart from other material, the content of carbon is very important. It should not be more that 0.25 percent as it would accelerate corrosion and which will not only reduce the life of building but also will increase periodical repairing work.
Normally in advanced countries, people don't buy steel, but they buy 'Readymade cut bars' as per designed length and shape i.e. as per bar bending schedule.
They have to be simply placed in position. But here also you need to exercise many of the above points.
When you buy 'Readymade Cut bars', check the following
(i) Check the shape and length of each type of bar as per bar bending schedule.
(ii) Check nos and stack each bar separately.
(iii) Always check the hooks, its shape and length.
(iv) Check the quantity.
Check whether the steel bars you buy bears a national certification like ASTM A706, JIS G, BS, ASTM A615, JIS G and IS 432 (Mild Steel Bar), IS (High Strength Deformed Steel Bar) etc. The certification assures you about its quality as well as the reputation of the manufacturer.
When you buy steel bars, you should read all the technical specifications which are either described in the product literature or on the manufacturer's website. We have to check whether the product specification represented by sales persons and the literature confirms or not. Try to understand and follow all the cautions of use and advice for use, etc. as per the written specifications in the literature. It is also necessary to read the terms and condition of warranty, guarantee, etc.
You may economise and save on each and every individual item, but you should not save on steel bars. They are the definite requirement of your house and directly related to safety and stability of your house.
It is advisable to provide steel bars as specified in drawing or as instructed by the structural consultant. Some people avoid consulting the structural consultant and providing the steel as per thumb rule to save the fees of the structural consultant. They forgot that every structure has carried different behaviour and one cannot use the same thumb rule for different structures. Do not get away by idiotic thumb rule of using this 2 to 3 kg of steel per Sq.ft. One thing we can tell you that thumb rules will raise your budget in future as they ultimately increase the cost of repairing work. They either excess your budget by over design or reduce the lifespan of the structure by under design.
You should also estimate the exact quantity of steel diameter wise. The wastage of steel bars will cost you high. You need to work out quantity in advance so you can bargain with the supplier or distributor.
You must search for the right supplier or distributor and their location. You should also find out whether it is directly available from the manufacturers or distributors or retailers etc. The price will definitely depend on from whom you buy the steel bars.
The cost of transportation, taxes and duties including the cost of loading and unloading at the site are the necessary point to remember as they also affect your budget while buying steel bars. Steel being heavy material, they form substantial weight and hence higher cost of the transportation.
Always use the popular brand of steel bars as they may have a certain quality. It is advisable to use the brand suggested by your structural consultant or use the government-approved brand or ISI brand.
The Price of steel bars vary between Rs 30 to Rs 60 per kg. Kamdhenu, Thermax, Tata Tiscon, Jindal, Essar, Vizag and Electro are the popular brands of steel bars in India who make different types of steel with different grade.
Always try to learn how to test the materials on site as well as in laboratory in case of bulk buying.
Study the above factors of steel bars and then select the right material and the supplier.
It is advisable to place written order if you are buying the large quantity. It should include specifications of steel bars, rates including taxes, transportation, and loading-unloading charges, etc. It should also include quantity, time of delivery, warranty, guarantee, terms of payment including advance.
When you receive steel bars at the site, please check the make, quantity and quality. Also check ISI marks, brand and whether there are any damages to the steel bars.
Also check the weight of steel bar received on site by at approved weighbridge.
Use this formula for the actual weight of steel (site) = Total weight of truck with steel bars ' The empty weight of truck (Weight without steel).
Do not stack directly on the ground as the ground moisture will rust it. Store the steel bars in godown and place wooden batten below them so they should not directly rest on ground.
If you are satisfied with the quality and quantity of the steel bars, then make payment as per the contract and obtain the receipt of payment. Preserve all the bills, product literature and the warrant/guarantee certificate, etc.
The steel bars are generally one-time purchase, and it has a long lasting service life when embedded in concrete. If we leave them in open environment, they get corroded fast. Hence try to use them as early as possible or store steel bars in warehouse.
You can buy steel bars in 8 mm (18 nos per bundle), 10 mm (12 nos per bundle), 12 mm (8 nos per bundle), and 16 mm (5 nos per bundle) sizes. They are commonly used for house construction. You can also buy steel bars with the bigger diameter of 20 mm (3 nos per bundle), 25 mm, 28 mm, and 32 mm, which are used for high-rise buildings only. They are generally packed in the bundle, and above 20 mm diameter, they are available in the single piece.
The standard length of steel bars is 12 meter, but you can select the length as per your requirement.
Nowadays Thermo Mechanically Treated (TMT) steel and Corrosion Resistance Steel (CRS) are also used in Reinforced Concrete Framed Structure construction. They have good elongation, bending strength, ductility and high tensile strength and high corrosion resistance.
If you want to learn more, please visit our website astm a615 rebar.
Previous: None
If you are interested in sending in a Guest Blogger Submission,welcome to write for us!
All Comments ( 0 )